Change search
Refine search result
15161718 851 - 884 of 884
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 851.
    Yin, Bo
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Core-shell nanoparticle and renewable resource plasticizers for PVC2011Licentiate thesis, comprehensive summary (Other academic)
  • 852.
    Yin, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Aminlashgari, Nina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Yang, Xi
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Glucose esters as biobased PVC plasticizers2014In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 58, p. 34-40Article in journal (Refereed)
    Abstract [en]

    Utilization of glucose, produced by liquefaction of cellulose or other abundant biomass sources, as raw material for production of green plasticizers would offer an attractive alternative to traditional phthalate plasticizers. Three glucose hexanoate esters (GHs) were synthesized by one-step reaction and evaluated as green plasticizers for poly(vinyl chloride) (PVC). The esterification was carried out for three different time periods to obtain plasticizers with different number of hexanoate groups, as the degree of substitution could influence the miscibility between PVC and GHs. A fast and powerful laser desorption ionization-mass spectrometry (LDI-MS) method was developed to obtain molecular level structural information of the plasticizer structures. All the GHs showed good miscibility with PVC and the GH blends exhibited better mechanical properties, in the form of higher strain at break and lower modulus, as compared to glucose pentaacetate (GPA) and sucrose octaacetate (SOA) blends that were studied in comparison. Altogether the results indicate that the synthesized glucose esters have large potential as green PVC plasticizers and they could be a promising option to overcome the environmental problems caused by phthalate plasticizers.

  • 853.
    Yin, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Core-shell nanoparticle-plasticizers for design of high-performance polymeric materials with improved stiffness and toughness2011In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, no 24, p. 8670-8677Article in journal (Refereed)
    Abstract [en]

    Core-shell nanoparticle-plasticizers were synthesized and blended with PVC in an attempt to simultaneously improve the toughness and stiffness of the resulting materials. Halloysite, kaolin and silicon dioxide nanofillers, representing acicular, layered and spherical morphologies, were surface-grafted with poly(butylene adipate) (PBA). The surface-grafting was confirmed by FTIR and the amount of PBA grafted on the surface was determined by TGA. In the case of halloysite and silicon dioxide nanoparticles their dispersion and miscibility in the PVC matrix were remarkably improved by the surface-grafting as shown by SEM, tensile testing and DMA. The tensile stress at break for the PVC films containing 5 wt% surface-treated halloysite nanoparticles increased 15%, modulus by 65% and the strain at break was 30 times higher compared to PVC containing 5 wt% untreated halloysite nanoparticles. The PVC films containing 5 wt% surface-treated silicon dioxide nanoparticles exhibited remarkably higher strain at break values compared to plain PVC/silicon dioxide composites, but also somewhat lower stress at break values probably due to the considerably higher amount of PBA grafted on the silicon dioxide surfaces. The higher storage modulus for PVC with surface modified silicon dioxide, however, still indicates higher stiffness for the material containing surface treated nanoparticles. Altogether the results show that the nanoparticle-plasticizer concept could be applied to simultaneously improve the toughness and stiffness of the materials and further improvements could be achieved after optimization of the number of PBA chains and their molecular weight.

  • 854.
    Yin, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Oligomeric Isosorbide Esters as Alternative Renewable Resource Plasticizers for PVC2011In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 119, no 4, p. 2400-2407Article in journal (Refereed)
    Abstract [en]

    Oligo(isosorbide adipate) (OSA), oligo(isosorbide suberate) (OSS), and isosorbide dihexanoate (SDH) were synthesized and evaluated as renewable resource alternatives to traditional phthalate plasticizers. The structure of the synthesized oligomers was confirmed by nuclear magnetic resonance spectroscopy (H-1-and C-13-NMR), and molecular weight was determined by size exclusion chromatograph. The plasticizers were blended with poly(vinyl chloride) (PVC), and the miscibility and properties of the blends were evaluated by differential scanning calorimetry, fourier transform infrared spectroscopy, tensile testing, and thermogravimetry. Especially the blends plasticized with SDH had almost identical properties with PVC/diisooctyl phthalate (DIOP) blends. The blends containing OSA and OSS plasticizers, based on dicarboxylic acids, had somewhat lower strain at break but higher stress at break and better thermal stability compared to the PVC/DIOP or PVC/SDH blends. All the synthesized isosorbide plasticizers showed potential as alternative PVC plasticizers.

  • 855.
    Yu, Wenbin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Degradation of polyethylene pipes distributing chlorinated water: depletion of stabilizers, release of degraded products and polymer degradation2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents the study of antioxidants depletions in chlorinated media (10 ppm Cl2 - and ClO2 - aqueous media), polyethylene pipes degradations scenarios and migration of the degraded species to aqueous phase. Pressure testing on pipes and squalane testing with controlled pH aqueous media (6.8 ± 0.2) containing either Cl2 or ClO2 were used for assessing the degradation products. Though squalane test used a liquid hydrocarbon instead of real plastic, it provided reliable data with an efficient and readily way of sampling. Medium density polyethylene pipes stabilized with hindered phenol and phosphite antioxidants were pressure tested with water containing 4 ppm chlorine dioxide (ClO2) at 90 °C as internal medium. The stabilizers were rapidly consumed towards the inner pipe wall; the rate of consumption was four times greater than in chlorinated (Cl2) aqueous (4 ppm, pH = 6.8) at the same temperature. The depletion of stabilizers occurred far into the pipe wall. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that in the surface layer which came into contact with the oxidizing medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains. The depletion rate of the antioxidant exposed to ClO2 - aqueous media was also four times faster than that exposed to Cl2 - aqueous media by squalane test. The aqueous media was extracted to condense the remaining antioxidants and the degraded species from the squalane solution. The absorption spectra from infrared spectroscopy illustrated that carbonyl groups exist in degraded species from both ClO2 - and Cl2 - aqueous, and chlorine-carbon bond presented only in ClO2 - aqueous. It was proved by liquid chromatography that the peaks of oxidizing species formed in ClO2 aqueous media were more intense and they were different from the ones degraded compounds in Cl2.

     

     

     

     

  • 856.
    Yu, Wenbin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Azhdar, Bruska
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Andersson, D.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Reitberger, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry (closed 20110630).
    Hassinen, J.
    Exova AB, Studsvik, Tystberga, Sweden.
    Hjertberg, T.
    Borealis AB, Stenungsund, Sweden.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Deterioration of polyethylene pipes exposed to water containing chlorine dioxide2011In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 96, no 5, p. 790-797Article in journal (Refereed)
    Abstract [en]

    Chlorine species used as disinfectants in tap water have a deteriorating effect on many materials including polyethylene. There are only very few scientific reports on the effect on polyethylene pipes of water containing chlorine dioxide. Medium-density polyethylene pipes stabilized with hindered phenol and phosphite antioxidants were pressure tested with water containing 4 ppm chlorine dioxide at 90 degrees C and pH = 6.8 as internal medium. The stabilizers were rapidly consumed towards the inner pipe wall; the rate of consumption was four times greater than in chlorinated water (4 ppm, pH = 6.8) at the same temperature. The depletion of stabilizer occurred far into the pipe wall. A supplementary study on a polymer analogue (squalane) containing the same stabilizer package showed that the consumption of the phenolic antioxidant was 2.5 times faster when exposed water containing chlorine dioxide than on exposure to chlorinated water. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that in the surface layer which came into contact with the oxidising medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains. Scanning electron microscopy showed that propagation of cracks through the pipe wall was assisted by polymer degradation.

  • 857.
    Yu, Wenbin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Characterization of degradation products from a phenolic antioxidant in squalane exposed to chlorinated aqueous mediaIn: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321Article in journal (Other academic)
  • 858.
    Yu, Wenbin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Reitberger, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE).
    Hjertberg, T.
    Oderkerk, J.
    Costa, F. R.
    Englund, V.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Chlorine dioxide resistance of different phenolic antioxidants in polyethylene2015In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 111, p. 1-6Article in journal (Refereed)
    Abstract [en]

    A series of polyethylene tape samples containing 8 different phenolic antioxidants (concentration = 0.1 +/- 0.01 wt.%) were exposed to water containing 10 ppm chlorine dioxide buffered to pH = 6.8 at 70 degrees C for different periods of time. The degradation rate and depletion time of the antioxidants in the polyethylene were obtained by oxidation induction time measurements using DSC. The majority of the tape samples (6 out of 8) showed a simple behaviour: the rate of antioxidant loss decreased and the antioxidant depletion time increased in linear fashion with increasing initial molar concentration of phenolic groups in the polymer. The tape that contained Hostanox O3 had a high initial phenolic concentration but it exhibited a short antioxidant depletion time due to the limited solubility of this antioxidant in polyethylene. Tapes containing Irganox 1330 and Cyanox 1790 showed antioxidant depletion times that were almost twice that of the other antioxidants with the same initial molar concentration of phenolic groups.

  • 859.
    Yu, Wenbin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Sedghi, Ehram
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Nawaz, Sohail
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hjertberg, T.
    Oderkerk, J.
    Costa, F. R.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Assessing the Long-­term Performance of Polyethylene Stabilised WithPhenolic Antioxidants Exposed to Water Containing Chlorine Dioxide2013In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 32, no 2, p. 359-365Article in journal (Refereed)
    Abstract [en]

    The addition of chlorine dioxide disinfectant to tap water prevents the spread of infection but has a serious drawback in that it degrades materials used in piping, including pipes made of polyethylene. Efficient methods are required to assess the long-term performance of different combinations of antioxidants and polyethylene grades. We have previously presented a screening method which exposes solutions of phenolic antioxidants in squalane (a liquid, low molar mass analogue of polyethylene) to 70 °C water containing either chlorine dioxide or chlorine. This method assesses the stability of the antioxidants towards these aqueous chlorinated media by determining the oxidation induction time through differential scanning calorimetry. The same experimental set-up with two modifications was used in developing a new method. A 0.3 mm thick polyethylene tape replaced the squalane phase and the supply of fresh water containing chlorine dioxide (10 ppm at pH = 6.8) was continuous; this required minimum attention from the operator over the longer exposure time periods used. Tapes of medium-density polyethylene containing 0.1 wt.% of six different phenolic antioxidants were studied. A linear relationship was established between the times to reach antioxidant depletion in the polyethylene tape samples and the times in the squalane samples (with the same antioxidants at the same concentration). A linear relationship was also found between the initial antioxidant consumption rates in polyethylene and squalane. Infrared spectroscopy and scanning electron microscopy of drawn samples revealed the onset of surface oxidation and surface embrittlement in tape samples exposed beyond the time for antioxidant depletion.

  • 860. Zammarano, Mauro
    et al.
    Krämer, Roland H
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Harris, Jr
    Ohlemiller, J
    Shields, R
    Rahatekar, S
    Lacerda, Silvia
    Gilman, W
    Flammability reduction of flexible polyurethane foams via carbon nanofiber network formation2008In: Polymers for Advanced Technologies, ISSN 1042-7147, E-ISSN 1099-1581, Vol. 19, no 6, p. 588-595Article in journal (Refereed)
    Abstract [en]

    Untreated polyurethane flexible foams (PUFs) are prone to rapid fire growth due to their low density and low thermal conductivity. Furthermore, the low viscosity of the decomposition products generates severe dripping that increases the fire hazard related to the combustion of PUFs. In fact, this downward flow of flaming liquid often results in a pool-fire that promotes flame propagation and boosts the rate of heat release (HRR) due to a significant increase in the burning area and to feed-back between the flame on the pool-fire and the residual foam. In this work the effect of nartoparticles, i.e., clays and carbon nanofibers (CNFs), on the HRR is investigated with special attention given to melt dripping. A modified cone calorimeter test has been developed for this purpose. It is shown that CNFs form an entangled fiber network which eliminates melt dripping and decreases the HRR.

  • 861.
    Zander, Zachary K.
    et al.
    University of Akron, United States.
    Hua, Geng
    University of Akron, United States.
    Wiener, Clinton G.
    University of Akron, United States.
    Vogt, Bryan D.
    University of Akron, United States.
    Becker, Matthew L.
    University of Akron, United States.
    Control of Mesh Size and Modulus by Kinetically Dependent Cross-Linking in Hydrogels2015In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, p. n/a-n/aArticle in journal (Refereed)
    Abstract [en]

    Kinetically controlled cross-linking processes produce mechanically distinguishable hydrogels using identical precursor chemistry. The oxime ligation demonstrates tunable reaction kinetics with pH and buffer strength, which induce changes in the structural features of hydrogels and determine their mechanical properties. Small-angle neutron scattering and swelling studies provide an insight into how structural properties correlate with mechanical properties for this hydrogel system.

  • 862. Zeng, Xianghui
    et al.
    Zhang, Yuning
    Wu, Zhihua
    Lundberg, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nystrom, Andreas M.
    Hyperbranched Copolymer Micelles as Delivery Vehicles of Doxorubicin in Breast Cancer Cells2012In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 50, no 2, p. 280-288Article in journal (Refereed)
    Abstract [en]

    Four types of drug nanoparticles (NPs) based on amphiphilic hyperbranched block copolymers were developed for the delivery of the chemotherapeutic doxorubicin (DOX) to breast cancer cells. These carriers have their hydrophobic interior layer composed of the hyperbranched aliphatic polyester, Boltorn (R) H30 or Boltorn (R) H40, that are polymers of poly 2,2-bis (methylol) propionic acid (bis-MPA), while the outer hydrophilic shell was composed of about 5 poly(ethylene glycol) (PEG) segments of 5 or 10 kDa molecular weight. A chemotherapeutic drug DOX, was further encapsulated in the interior of these polymer micelles and was shown to exhibit a controlled release profile. Dynamic light scattering and transmission electron microscopy analysis confirmed that the NPs were uniformly sized with a mean hydrodynamic diameter around 110 nm. DOX-loaded H30-PEG10k NPs exhibited controlled release over longer periods of time and greater cytotoxicity compared with the other materials developed against our tested breast cancer cell lines. Additionally, flow cytometry and confocal scanning laser microscopy studies indicated that the cancer cells could internalize the DOX-loaded H30-PEG10k NPs, which contributed to the sustained drug release, and induced more apoptosis than free DOX did. These findings indicate that the H30-PEG10k NPs may offer a very promising approach for delivering drugs to cancer cells. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 280-288, 2012

  • 863.
    Zhang, Jinbao
    et al.
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    Hao, Yan
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    Yang, Li
    Uppsala Univ, Dept Engn Sci, Nanotechnol & Funct Mat, Uppsala, Sweden..
    Mohammadi, Hajar
    Univ Isfahan, Dept Chem, Esfahan 8174673441, Iran..
    Vlachopoulos, Nick
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, CH G1 523, CH-1015 Lausanne, Switzerland..
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, CH G1 523, CH-1015 Lausanne, Switzerland..
    Sheibani, Esmaeil
    Univ Isfahan, Dept Chem, Esfahan 8174673441, Iran..
    Electrochemically polymerized poly (3, 4-phenylenedioxythiophene) as efficient and transparent counter electrode for dye sensitized solar cells2019In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 300, p. 482-488Article in journal (Refereed)
    Abstract [en]

    A new conducting polymer poly (3, 4-phenylenedioxythiophene) is synthesized by the electrochemical polymerization technique with different solvents. We find that solvents used in electrochemical polymerization play important roles for the catalytic activity and morphology of the formed conducting polymers. The obtained poly (3, 4-phenylenedioxythiophene) is for the first time employed as counter electrode electrocatalyst in dye sensitized solar cells with cobalt-based electrolytes. We demonstrate that a polymer prepared from a mixed acetonitrile-dichloromethane solvent exhibit higher catalytic activity for redox reactions, as compared to that from a single solvent, dichloromethane. The devices based on this mixed solvent-based polymer from a mixed solvents show a high power conversion efficiency of 5.97%. An additional advantageous feature of the electrochemically polymerized poly (3, 4-phenylenedioxythiophene) for solar cell applications is the high transparency in the visible and nearinfrared region. We also investigate the beneficial effect of the poly (3, 4-phenylenedioxythiophene) layer thickness on device performance, and concluded that the series resistance and charge transfer resistance are greatly influenced by the thickness of polymer, as evidenced by electrochemical impedance spectroscopy measurements. The optimal thickness for poly (3, 4-phenylenedioxythiophene) is about 100 nm. Furthermore, the high catalytic activity and transparency of the new conducting polymer as counter electrode shows great promise for other optoelectronic applications.

  • 864. Zhang, Yuning
    et al.
    Lundberg, Pontus
    Diether, Maren
    Porsch, Christian
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Janson, Caroline
    Lynd, Nathaniel A.
    Ducani, Cosimo
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hawker, Craig J.
    Nystrom, Andreas M.
    Histamine-functionalized copolymer micelles as a drug delivery system in 2D and 3D models of breast cancer2015In: Journal of materials chemistry. B, ISSN 2050-750X, E-ISSN 2050-7518, Vol. 3, no 12, p. 2472-2486Article in journal (Refereed)
    Abstract [en]

    Histamine functionalized block copolymers based on poly(allyl glycidyl ether)-b-poly(ethylene oxide) (PAGE-b-PEO) were prepared with different ratios of histamine and octyl or benzyl groups using UV-initiated thiol-ene click chemistry. At neutral pH, the histamine units are uncharged and hydrophobic, while in acidic environments, such as in the endosome, lysosomes, or extracellular sites of tumours, the histamine groups are positively charged and hydrophilic. pH responsible polymer drug delivery systems is a promising route to site specific delivery of drugs and offers the potential to avoid side effects of systemic treatment. Our detailed in vitro experiments of the efficacy of drug delivery and the intracellular localization characteristics of this library of NPs in 2D and 3D cultures of breast cancer revealed that the 50% histamine-modified polymer loaded with DOX exhibited rapid accumulation in the nucleus of free DOX within 2 h. Confocal studies showed enhanced mitochondrial localization and lysosomal escape when compared to controls. From these combined studies, it was shown that by accurately tuning the structure of the initial block copolymers, the resulting self-assembled NPs can be designed to exploit histamine as an endosomal escape trigger and the octyl/benzyl units give rise to a hydrophobic core resulting in highly efficacious drug delivery systems (DDS) with control over intracellular localization. Optimization and rational control of the intracellular localization of both DDS and the parent drug can give nanomedicines a substantial increase in efficacy and should be explored in future studies.

  • 865.
    Zhao, Weifeng
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. Sichuan University.
    Chemical Pathways to Electrically Conductive Hemicellulose Hydrogels2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hydrogels have been extensively explored and are widely used in diverse biomedical applications, such as scaffolds for tissue engineering and vehicles for drug delivery. As one type of important natural polymer-based hydrogel, hemicellulose hydrogels have interesting attributes, including being renewable, non-toxic, biocompatible, biodegradable, and abundantly available. A prominent way to extend their potential is by combining them with desirable properties from other materials. The focus of this thesis is to develop a new family of electrically conductive hemicellulose-based hydrogels (ECHHs) using O-acetyl-galactoglucomannan (AcGGM) and aniline oligomers through different chemical pathways.

    A first approach to synthesize the ECHHs includes two steps: first, carboxylated AcGGM (C-AcGGM) is dissolved with glycidyl methacrylate, followed by polymerization initiated by ammonium persulfate; second, the resulting hydrogels are covalently coupled to varying amounts of aniline tetramer (AT), which is homogeneously distributed throughout the network. The swelling ratios of C-AcGGM hydrogels decrease as the degree of substitution of maleic anhydride increases. The swelling ratios and conductivities of ECHHs are tuned by the AT content.

    To develop a simpler and greener approach to synthesize ECHHs under ambient conditions, AcGGM is in-situ cross-linked in the presence of aniline pentamer (AP) in basic water. Hydrogel equilibrium swelling ratios (ESRs) vary from 12.7 to 10.4, regulated by cross-linker concentration. The ESRs are also tuned from 9.6 to 6.0 by changing the AP contents from 10 % (w/w) to 40 % (w/w) while simultaneously altering conductivities from 9.05×10-9 to 1.58×10-6 S/cm.

    ECHHs with controllable conductivity, tunable swelling behavior and acceptable mechanical properties extend the applications of hemicellulose to include e.g. biosensors and electronic devices.

  • 866.
    Zhao, Weifeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Glavas, Lidija
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    A robust pathway to electrically conductive hemicellulose hydrogels with high and controllable swelling behavior2014In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 55, no 13, p. 2967-2976Article in journal (Refereed)
    Abstract [en]

    A robust pathway to synthesize electrically conductive hemicellulose hydrogels (ECHHs) based on O-acetylgalactoglucomannan (AcGGM) and conductive aniline tetramer (AT) is presented. These ECHHs were obtained by functionalizing carboxylated AcGGM with glycidyl methacrylate (GMA) and subsequently covalently immobilizing AT onto GMA. Hydrogel swelling ratios (SRs) were regulated by the degree of substitution (DS) of the carboxylated AcGGM, the maximum varied as follows: SRDS=1.14 < SRDS=0.60 < SRDS=0.24. The SR can also be tuned from 548% to 228% by changing the AT contents from 10% (w/w) to 40% (w/w) while simultaneously altering conductivities from 2.93 x 10(-8) to 1.12 x 10(-6) S/cm. Free-standing ECHHs with tunable conductivity and degree of swelling, as presented herein, have a broad potential for biomedical applications.

  • 867.
    Zhao, Weifeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. Sichuan University, China .
    Glavas, Lidija
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Facile and Green Approach towards Electrically Conductive Hemicellulose Hydrogels with Tunable Conductivity and Swelling Behavior2014In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, no 14, p. 4265-4273Article in journal (Refereed)
    Abstract [en]

    A one-pot reaction to synthesize electrically conductive hemicellulose hydrogels (ECHHs) is developed via a facile and green approach in water and at ambient temperature. ECHHs were achieved by cross-linking O-acetyl-galactoglucomannan (AcGGM) with epichlorohydrin in the presence of conductive aniline pentamer (AP) and were confirmed by infrared spectroscopy (IR) and elemental analysis. All hydrogels had macro-porous structures, and the thermal stability of ECHHs was improved by the addition of AP. Hydrogel equilibrium swelling ratios (ESRs) varied from 13.7 to 11.4 and were regulated by cross-linker concentration. The ESRs can also be tuned from 9.6 to 6.0 by changing the AP content level from 10 to 40% (w/w) while simultaneously altering conductivity from 9.05 x 10(-9) to 1.58 X 10(-6) S/cm. ECHHs with controllable conductivity, tunable swelling behavior, and acceptable mechanical properties have great potential for biomedical applications, such as biosensors, electronic devices, and tissue engineering.

  • 868.
    Zhao, Yadong
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Towards Large-scale and Feasible Exploitation of Tunicate Cellulose and Cellulose Nanocrystals for Different Applications2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Tunicates are a group of filter-feeding animals that live in the ocean. They are widely distributed throughout the world and are a major contributor to the fouling problem in aquaculture. In addition to their natural abundance, large-scale farming will further render them readily available in high quantities, and they should instead be providing us food, energy, chemicals and materials. As tunicates are the sole known animal group synthesizing cellulose, the primary target for this bioresources exploitation should be cellulose preparation and application. Moreover, cellulose exploitation should be conducted in both a technically and economically feasible manner.

    Among the tunicates, Ciona intestinalis (termed Ciona hereafter) is one of the most abundant species in Norwegian and Swedish coastal waters. Upon comprehensive quantification of the principal chemical compositions, cellulose has been confirmed to exist as cellulose-protein fibrils cemented by non-cellulose glycans and lipids and is almost exclusively present in the Ciona tunic fraction. Using the tunic as raw material, Ciona cellulose was prepared following a unique prehydrolysis-kraft cooking-bleaching sequence with a yield of 21.64% and by a modified Updegraff method with a yield of 23.65% on a dried ash-free mass basis. To improve the Ciona cellulose dispersibility and processability, Ciona cellulose nanocrystals (CNs) were prepared using different processes, namely acid hydrolysis, 2,2,6,6‑tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation and enzymatic hydrolysis as well as acid hydrolysis followed by TEMPO-mediated oxidation. The CN preparation yield was 30.0-73.4%, depending on the process applied.

    By conducting comprehensive characterizations, it was found that the Ciona cellulose was nearly 100% pure, with a large weight average degree of polymerization (DPw=4200), a high surface area (133 m2/g), a large aspect ratio (length of several micrometres and diameter of ~16 nm), a high crystallinity (89%) in the form of nearly pure Iβ crystals, and a good thermal stability (onset degradation temperature of 226 ºC). When obtained in membrane form, the cellulose preserved the native interwoven microfibril network structure in the original tunic. It had a high ductility (tensile strain of 19.24%) in the wet state and good mechanical strength (tensile strength of 41.19 MPa and Young’s Modulus of 1.98 GPa) when dried. The CNs obtained were smaller in DPw, shorter in morphological size (length), similar or higher in crystallinity and more thermally stable than the starting cellulose to different extents and with different charged structures and charge contents dependent on the method/procedure used.

    Several applications have been examined. First, the Ciona cellulose in pulp form was utilized in the fabrication of sponge cloth to replace cotton, and the product obtained was of similar quality to the commercial one made from cotton. Second, the Ciona cellulose in membrane form was tested in the cultivation of human umbilical vein endothelial cells and mouse NIH‑3T3 cells for evaluations of cell proliferation performance and medical application potential. The performance was very positive. Third, the Ciona cellulose membrane and two CNs were applied as the matrix for high-quality zinc-blende CdSe/CdS core/shell nanocrystal quantum dots (QDs) for the development of mechanically strong and high-performance fluorescent material. The QDs were firmly attached to the Ciona CNs with uniform monolayer distribution and a high packing density. The obtained composites preserved both the high-quality optical properties from the QDs and the matrix morphology and thus expectedly the excellent mechanical properties from the cellulose. Finally, the Ciona CNs were processed to composite films cemented by konjac glucomannan for material development. Newly introduced hydrogen bonds between these two compatible polysaccharides and thus strong cementing effects were observed. The composite films showed excellent mechanical properties in addition to improved transparency, thermal stability and hydrophobicity compared with the CN’s neat films.

    Feasible tunicate cellulose exploitation demands the sound large-scale farming of Ciona for the highest possible cellulose content in the farmed animal, the exploitation of species other than Ciona, the complete utilization of fractions other than the tunic used and the value-added productions of other by-products. Composition quantification of the adult Ciona specimens collected from different farms showed that the carbohydrate content was linearly correlated with the body weight, which in turn was affected by the farm location, deployment time and sub-sea depth of the settling structures. Through analysing the Ciona intestinal content, it was found that both eukaryotes and prokaryotes contributed to the diet of the animal, and their quantities were positively correlated with the animal size (body weight). The tunics of three other tunicate species, Halocynthia roretzi, Styela plicata, and Ascidia sp., have been examined for tunicate cellulose preparation following the prehydrolysis-kraft cooking‑bleaching procedure. They were all found to be good sources for similar quality tunicate cellulose exploitation, thus verifying the universal applicability of the procedure. Based on more detailed chemical composition analyses, all the fractions other than the tunic, termed the inner body tissues fraction, from all four tunicate species were found to have excellent nutritional values: a high protein content with good quality amino acids and high contents of omega-3 (n-3) fatty acids and essential elements. Their toxic element contents were under the regulated limits for human food. They should therefore all be explored as human food sources. Furthermore, many different chemical structures, many of which were found for the first time, were present in the tunicate animals studied, ranging from collagens, glycosaminoglycans, and sterols to phospholipids. These structures should be explored as various bioactive by‑products during tunicate cellulose exploitation. For example, the prepared Ciona lipids had a high content of n-3 fatty acids, which presented mainly in the form of phospholipids. They should be an excellent alternative to markedly high value fish oils, but with a higher bioavailability.

    The techniques and knowledge obtained by this study will provide a basis for the promising large-scale and feasible exploitation of tunicate cellulose and cellulose nanocrystals for different applications.

  • 869.
    Zhao, Yadong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Moser, Carl
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindström, Mikael E
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Cellulose Nanofibers from Softwood, Hardwood, and Tunicate: Preparation-Structure-Film Performance Interrelation2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 15, p. 13508-13519Article in journal (Refereed)
    Abstract [en]

    This work reveals the structural variations of cellulose nanofibers (CNF) prepared from different cellulose sources, including softwood (Picea abies), hardwood (Eucalyptus grandis × E. urophylla), and tunicate (Ciona intestinalis), using different preparation processes and their correlations to the formation and performance of the films prepared from the CNF. Here, the CNF are prepared from wood chemical pulps and tunicate isolated cellulose by an identical homogenization treatment subsequent to either an enzymatic hydrolysis or a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation. They show a large structural diversity in terms of chemical, morphological, and crystalline structure. Among others, the tunicate CNF consist of purer cellulose and have a degree of polymerization higher than that of wood CNF. Introduction of surface charges via the TEMPO-mediated oxidation is found to have significant impacts on the structure, morphology, optical, mechanical, thermal, and hydrophobic properties of the prepared films. For example, the film density is closely related to the charge density of the used CNF, and the tensile stress of the films is correlated to the crystallinity index of the CNF. In turn, the CNF structure is determined by the cellulose sources and the preparation processes. This study provides useful information and knowledge for understanding the importance of the raw material for the quality of CNF for various types of applications.

  • 870.
    Zhao, Yadong
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Tagami, Ayumu
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Dobele, Galina
    Latvian State Inst Wood Chem, 27 Dzerbenes Str, LV-1006 Riga, Latvia..
    Lindström, Mikael E.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Sevastyanova, Olena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    The Impact of Lignin Structural Diversity on Performance of Cellulose Nanofiber (CNF)-Starch Composite Films2019In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 11, no 3, article id 538Article in journal (Refereed)
    Abstract [en]

    Lignin fractions having different molecular weights and varied chemical structures isolated from kraft lignins of both softwood and hardwood via a sequential solvent fractionation technique were incorporated into a tunicate cellulose nanofibers (CNF)-starch mixture to prepare 100% bio-based composite films. The aim was to investigate the impact of lignin structural diversity on film performance. It was confirmed that lignin's distribution in the films was dependent on the polarity of solvents used for fractionation (acetone > methanol > ethanol > ethyl acetate) and influenced the optical properties of the films. The -OH group content and molecular weight of lignin were positively related to film density. In general, the addition of lignin fractions led to decrease in thermal stability and increase in Young's modulus of the composite films. The modulus of the films was found to decrease as the molecular weight of lignin increased, and a higher amount of carboxyl and phenolic -OH groups in the lignin fraction resulted in films with higher stiffness. The thermal analysis showed higher char content formation for lignin-containing films in a nitrogen atmosphere with increased molecular weight. In an oxygen atmosphere, the phenol content, saturated side chains and short chain structures of lignin had impacts on the maximum decomposition temperature of the films, confirming the relationship between the chemical structure of lignin and thermo-oxidative stability of the corresponding film. This study addresses the importance of lignin diversities on composite film performance, which could be helpful for tailoring lignin's applications in bio-based materials based on their specific characteristics.

  • 871.
    Zhao, Yadong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Wang, Miao
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Fatty acid and lipid profiles with emphasis on n-3 fatty acids and phospholipids from Ciona intestinalis2015In: Lipids, ISSN 0024-4201, E-ISSN 1558-9307, Vol. 50, no 10, p. 1009-1027Article in journal (Refereed)
    Abstract [en]

    In order to establish Ciona intestinalis as a new bioresource for n-3 fatty acids-rich marine lipids, the animal was fractionated into tunic and inner body tissues prior to lipid extraction. The lipids obtained were further classified into neutral lipids (NL), glycolipids (GL) and phospholipids (PL) followed by qualitative and quantitative analysis using GC-FID, GC-MS, H-1 NMR, 2D NMR, MALDI-TOF-MS and LC-ESI-MS methods. It was found that the tunic and inner body tissues contained 3.42-4.08 % and 15.9-23.4 % of lipids respectively. PL was the dominant lipid class (42-60 %) irrespective of the anatomic fractions. From all lipid fractions and classes, the major fatty acids were 16:0, 18:1n-9, C20:1n-9, C20:5n-3 (EPA) and C22:6n-3 (DHA). The highest amounts of long chain n-3 fatty acids, mainly EPA and DHA, were located in PL from both body fractions. Cholestanol and cholesterol were the dominant sterols together with noticeable amounts of stellasterol, 22 (Z)-dehydrocholesterol and lathosterol. Several other identified and two yet unidentified sterols were observed for the first time from C. intestinalis. Different molecular species of phosphatidylcholine (34 species), sphingomyelin (2 species), phosphatidylethanolamine (2 species), phosphatidylserine (10 species), phosphatidylglycerol (9 species), ceramide (38 species) and lysophospholipid (5 species) were identified, representing the most systematic PL profiling knowledge so far for the animal. It could be concluded that C. intestinalis lipids should be a good alternative for fish oil with high contents of n-3 fatty acids. The lipids would be more bioavailable due to the presence of the fatty acids being mainly in the form of PL.

  • 872.
    Zheng, Chao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Li, Dongfang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardants2019In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 34, no 1, p. 96-106Article in journal (Refereed)
    Abstract [en]

    Sustainable thermal insulating materials produced from cellulosic fibers provide a viable alternative to plastic insulation foams. Industrially available, abundant, and inexpensive mechanical pulp fiber and recycled textile fiber provide potential raw materials to produce thermal insulating materials. To improve the fire retardancy of low-density thermal insulating materials produced from recycled cotton denim and mechanical pulp fibers, bio-based fire retardants, such as sulfonated kraft lignin, kraft lignin, and nanoclays, were coated onto sustainable insulating material surfaces to enhance their fire retardancy. Microfibrillated cellulose was used as a bio-based binder in the coating formula to disperse and bond the fire-retardant particles to the underlying thermal insulating materials. The flammability of the coated thermal insulating materials was tested using a single-flame source test and cone calorimetry. The results showed that sulfonated kraft lignin-coated cellulosic thermal insulating materials had a better fire retardancy compared with that for kraft lignin with a coating weight of 0.8 kg/m(2). Nanoclay-coated samples had the best fire retardancy and did not ignite under a heat flux of 25 kW/m(2), as shown by cone calorimetry and single-flame source tests, respectively. These cost-efficient and bio-based fire retardants have broad applications for improving fire retardancy of sustainable thermal insulating materials.

  • 873.
    Zhong, Qi
    et al.
    Zhejiang Sci Tech Univ, Natl Base Int Sci & Technol Cooperat Text & Consu, Engn Res Ctr Ecodyeing & Finishing Text, Key Lab Adv Text Mat & Mfg Technol,Minist Educ, Hangzhou 310018, Zhejiang, Peoples R China.;Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat Fachgebiet Phys Weicher Mat, James Franck Str 1, D-85748 Garching, Germany..
    Mi, Lei
    Zhejiang Sci Tech Univ, Natl Base Int Sci & Technol Cooperat Text & Consu, Engn Res Ctr Ecodyeing & Finishing Text, Key Lab Adv Text Mat & Mfg Technol,Minist Educ, Hangzhou 310018, Zhejiang, Peoples R China..
    Metwalli, Ezzeldin
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat Fachgebiet Phys Weicher Mat, James Franck Str 1, D-85748 Garching, Germany..
    Biessmann, Lorenz
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat Fachgebiet Phys Weicher Mat, James Franck Str 1, D-85748 Garching, Germany..
    Philipp, Martine
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat Fachgebiet Phys Weicher Mat, James Franck Str 1, D-85748 Garching, Germany..
    Miasnikova, Anna
    Univ Potsdam, Inst Chem, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Laschewsky, Andre
    Univ Potsdam, Inst Chem, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany.;Fraunhofer Inst Angew Polymerforschung, Geiselbergstr 69, D-14476 Potsdam, Germany..
    Papadakis, Christine M.
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat Fachgebiet Phys Weicher Mat, James Franck Str 1, D-85748 Garching, Germany..
    Cubitt, Robert
    Inst Laue Langevin, 6 Rue Jules Horowitz, F-38000 Grenoble, France..
    Schwartzkopf, Matthias
    Deutsch Elektronen Synchrotron DESY, Photon Sci, Notkestr 85, D-22607 Hamburg, Germany..
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.
    Wang, Jiping
    Zhejiang Sci Tech Univ, Natl Base Int Sci & Technol Cooperat Text & Consu, Engn Res Ctr Ecodyeing & Finishing Text, Key Lab Adv Text Mat & Mfg Technol,Minist Educ, Hangzhou 310018, Zhejiang, Peoples R China..
    Mueller-Buschbaum, Peter
    Tech Univ Munich, Phys Dept, Lehrstuhl Funkt Mat Fachgebiet Phys Weicher Mat, James Franck Str 1, D-85748 Garching, Germany..
    Effect of chain architecture on the swelling and thermal response of star-shaped thermo-responsive (poly(methoxy diethylene glycol acrylate)-block-polystyrene)(3) block copolymer films2018In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, no 31, p. 6582-6594Article in journal (Refereed)
    Abstract [en]

    The effect of chain architecture on the swelling and thermal response of thin films obtained from an amphiphilic three-arm star-shaped thermo-responsive block copolymer poly(methoxy diethylene glycol acrylate)-block-polystyrene ((PMDEGA-b-PS)(3)) is investigated by in situ neutron reflectivity (NR) measurements. The PMDEGA and PS blocks are micro-phase separated with randomly distributed PS nanodomains. The (PMDEGA-b-PS)(3) films show a transition temperature (TT) at 33 degrees C in white light interferometry. The swelling capability of the (PMDEGA-b-PS)(3) films in a D2O vapor atmosphere is better than that of films from linear PS-b-PMDEGA-b-PS triblock copolymers, which can be attributed to the hydrophilic end groups and limited size of the PS blocks in (PMDEGA-b-PS)(3). However, the swelling kinetics of the as-prepared (PMDEGA-b-PS)(3) films and the response of the swollen film to a temperature change above the TT are significantly slower than that in the PS-b-PMDEGA-b-PS films, which may be related to the conformation restriction by the star-shape. Unlike in the PS-b-PMDEGA-b-PS films, the amount of residual D2O in the collapsed (PMDEGA-b-PS)(3) films depends on the final temperature. It decreases from (9.7 +/- 0.3)% to (7.0 +/- 0.3)% or (6.0 +/- 0.3)% when the final temperatures are set to 35 degrees C, 45 degrees C and 50 degrees C, respectively. This temperature-dependent reduction of embedded D2O originates from the hindrance of chain conformation from the star-shaped chain architecture.

  • 874.
    Zhou, Xiamo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Haraldsson, Klas Tommy
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Nania, Salvatore
    Karolinska Univ Hosp, Dept Clin Sci Intervent & Technol, Novum Hiss 6A, S-14196 Huddinge, Sweden..
    Ribet, Federico
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Palano, Giorgia
    Karolinska Univ Hosp, Dept Clin Sci Intervent & Technol, Novum Hiss 6A, S-14196 Huddinge, Sweden..
    Heuchel, Rainer
    Karolinska Univ Hosp, Dept Clin Sci Intervent & Technol, Novum Hiss 6A, S-14196 Huddinge, Sweden..
    Loehr, Matthias
    Karolinska Univ Hosp, Dept Clin Sci Intervent & Technol, Novum Hiss 6A, S-14196 Huddinge, Sweden..
    van der Wijngaart, Wouter Metsola
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Human Cell Encapsulation in Gel Microbeads with Cosynthesized Concentric Nanoporous Solid Shells2018In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 21, article id 1707129Article in journal (Refereed)
    Abstract [en]

    Encapsulation of therapeutic cells in core-shell microparticles has great promise for the treatment of a range of health conditions. Unresolved challenges related to control of the particle morphology, mechanical stability, and immunogenicity hinder dissemination of this promising approach. Here, a novel polymer material for cell encapsulation and a combined novel, easy to control, synthesis method are introduced. Core-shell cell encapsulation is demonstrated with a concentric core-shell morphology formed during a single UV exposure, resulting in particles that consist of a synthetic hydrogel core of polyethylene glycol diacrylate and a solid, but porous, shell of off-stoichiometric thiol-ene. The encapsulated human cells in 100 mu m diameter particles have >90% viability. The average shell thickness is controlled between 7 and 13 mu m by varying the UV exposure, and the shell is measured to be permeable to low molecular weight species (<180 Da) but impermeable to higher molecular weight species (>480 Da). The unique material properties and the orthogonal control of the microparticle core size, shell thickness, shell permeability, and shell surface properties address the key unresolved challenges in the field, and are expected to enable faster translation of novel cell therapy concepts from research to clinical practice.

  • 875. Zhu, Hongli
    et al.
    Luo, Wei
    Ciesielski, Peter N.
    Fang, Zhiqiang
    Zhu, J. Y.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Himmel, Michael E.
    Hu, Liangbing
    Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications2016In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 116, no 16, p. 9305-9374Article, review/survey (Refereed)
    Abstract [en]

    With the arising of global climate change and resource shortage, in recent years, increased attention has been paid to environmentally friendly materials. Trees are sustainable and renewable materials, which give us shelter and oxygen and remove carbon dioxide from the atmosphere. Trees are a primary resource that human society depends upon every day, for example, homes, heating, furniture, and aircraft. Wood from trees gives us paper, cardboard, and medical supplies, thus impacting our homes, school, work, and play. All of the above-mentioned applications have been well developed over the past thousands of years. However, trees and wood have much more to offer us as advanced materials, impacting emerging high-tech fields, such as bioengineering, flexible electronics, and clean energy. Wood naturally has a hierarchical structure, composed of well-oriented microfibers and tracheids for water, ion, and oxygen transportation during metabolism. At higher magnification, the walls of fiber cells have an interesting morphology-a distinctly mesoporous structure. Moreover, the walls of fiber cells are composed of thousands of fibers (or macrofibrils) oriented in a similar angle. Nanofibrils and nanocrystals can be further liberated from macrofibrils by mechanical, chemical, and enzymatic methods. The obtained nanocellulose has unique optical, mechanical, and barrier properties and is an excellent candidate for chemical modification and reconfiguration. Wood is naturally a composite material, comprised of cellulose, hemicellulose, and lignin. Wood is sustainable, earth abundant, strong, biodegradable, biocompatible, and chemically accessible for modification; more importantly, multiscale natural fibers from wood have unique optical properties applicable to different kinds of optoelectronics and photonic devices. Today, the materials derived from wood are ready to be explored for applications in new technology areas, such as electronics, biomedical devices, and energy. The goal of this study is to review the fundamental structures and chemistries of wood and wood-derived materials, which are essential for a wide range of existing and new enabling technologies. The scope of the review covers multiscale materials and assemblies of cellulose, hemicellulose, and lignin as well as other biomaterials derived from wood, in regard to their major emerging applications. Structure properties application relationships will be investigated in detail. Understanding the fundamental properties of these structures is crucial for designing and manufacturing products for emerging applications. Today, a more holistic understanding of the interplay between the structure, chemistry, and performance of wood and wood-derived materials is advancing historical applications of these materials. This new level of understanding also enables a myriad of new and exciting applications, which motivate this review. There are excellent reviews already on the classical topic of woody materials, and some recent reviews also cover new understanding of these materials as well as potential applications. This review will focus on the uniqueness of woody materials for three critical applications: green electronics, biological devices, and energy storage and bioenergy.

  • 876.
    Zhu Ryberg, Yingzhi
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Wood Hydrolysate for Renewable Products2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Renewable biomass has been used by mankind for a long time for different purposes, from simply food to industrial products. Among a large family of polysaccharides, hemicellulose is non-edible but has shown a potential in many industrial fields such as medicine, agriculture and packaging. However, a complicated process is usually required to extract highly purified hemicellulose for further applications, which makes it not practical and economical for real industrial applications.

    This thesis presents the utilization of a wood hydrolysate which was simply upgraded and recovered instead of being highly purified from the liquid by-product in the pulp industry. This softwood hydrolysate is rich in hemicellulose, O-acetyl galactoglucomannan (AcGGM), and also contains some lignin.

    Films and coatings were produced based on this wood hydrolysate by blending with two other polysaccharide co-components, carboxymethyl cellulose (CMC) and chitosan. Different recipes with a variety of concentrations and compositions were prepared. For comparison, highly purified AcGGM-based films and coatings were also produced.

    Mechanical properties and water vapor and oxygen barrier properties of the films and coatings were investigated. It was found that as a co-component, chitosan improved the mechanical properties best, and CMC gave better oxygen barrier properties at both 50% and 80% relative humidity. The wood-hydrolysate-based films gave much lower oxygen permeability (OP) values than AcGGM-based films.

    In order to reveal why the less purified wood hydrolysate gave a better oxygen barrier, both theoretical and experimental studies were carried out. A group calculation based on Hansen’s Solubility parameter theory (HSP) showed that there were strong interactions between lignin and AcGGM in the wood hydrolysate and also that CMC was more compatible with wood hydrolysate/AcGGM than chitosan. These led to an affinity between components and gave a more compact molecular structure, and thus a smaller free volume in the matrix. This interpretation was in agreement with the Positron annihilation lifetime spectra (PALS) data, which showed that wood-hydrolysate-based films had a smaller free volume (hole size) and narrower distribution than AcGGM-based films. It also showed that CMC-co-component films had smaller hole radii in the matrix than chitosan-co-component films. Thermal properties and FTIR also shed light on the influence and nature of these interactions.

     

  • 877.
    Zhu Ryberg, Yingzhi
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Conceptual approach to renewable barrier film design based on wood hydrolysate2011In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, no 4, p. 1355-1362Article in journal (Refereed)
    Abstract [en]

    Biomass is converted to oxygen barriers through a conceptually unconventional approach involving the preservation of the biomass native interactions and macromolecular components and enhancing the effect by created interactions With a co-component. A combined calculation/assessment model is elaborated to understand, quantify, and predict which compositions that provide an intermolecular affinity high enough to mediate the molecular packing needed to create a functioning barrier. The biomass used is a wood hydrolysate, a polysaccharide-rich but not highly refined mixture where a fair amount of the native intermolecular and intramolecular hernicelluloses-lignin interactions are purposely preserved, resulting in barriers with very low oxygen permeabilities (OP) both at 50 and 80% relative humidity and, considerably lower OPs than coatings based on the corresponding highly purified spruce hemicellulose, O-acetyl galactoglucomannan (AcGGM). The component interactions and, mutual affinities effectively mediate an immobilization of the chain segments in a dense disordered structure, modeled through the Hansen's solubility parameter concept and quantified on the nanolength scale by positron annihilation lifetime spectrum (PALS).

  • 878. Zorn, Anna-Marie
    et al.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Carlmark Malkoch, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Barner-Kowollik, Christopher
    High temperature synthesis of vinyl terminated polymers based on dendronized acrylates: a detailed product analysis study2011In: POLYMER CHEMISTRY, ISSN 1759-9954, Vol. 2, no 5, p. 1163-1173Article in journal (Refereed)
    Abstract [en]

    The combination of dendrons and high temperature acrylate polymerization represents a viable route to form dendronized macromonomers. Dendronized acrylates based on 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) were synthesized using dendrimer synthesis and click chemistry (copper catalyzed azide alkyne cycloaddition (CuAAC)). The synthesis was carried out up to the 3rd generation and with a carbon spacer length of 6 or 9 between the acrylic function and the dendron core. These dendronized acrylates were subjected to auto-initiated high temperature acrylate polymerization. The polymerization was performed at 140 degrees C in a 5 wt% solution of hexyl acetate with a 2,2'-azobis(isobutyronitrile) (AIBN) concentration of 5 x 10(-3) g mol(-1). The vinyl terminated polymers were in-depth characterized via size exclusion chromatography (SEC) and size exclusion chromatography coupled to electrospray ionization mass spectrometry (SEC-ESI-MS) to assess the generated product spectrum and the efficiency of the process. The achievable number average molecular weight, M-n, was between 1700 and 4400 g mol(-1). The degree of polymerization, DPn, decreases with increasing generations of the dendronized acrylates from 6.3 to 3.4. The purity of vinyl terminated oligomers containing a geminal double bond is up to 83%, with the dendronized acrylates of the 1st generation providing the best result. Moderate deprotection of the acetonide groups occurred spontaneously during the macromonomer formation process and reached its maximum at generation 3.

  • 879.
    Öberg Hed, Kim
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Advanced polymeric scaffolds for functional materials in biomedical applications2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Advancements in the biomedical field are driven by the design of novel materials with controlled physical and bio-interactive properties. To develop such materials, researchers rely on the use of highly efficient reactions for the assembly of advanced polymeric scaffolds that meet the demands of a functional biomaterial. In this thesis two main strategies for such materials have been explored; these include the use of off-stoichiometric thiol-ene networks and dendritic polymer scaffolds. In the first case, the highly efficient UV-induced thiol-ene coupling (TEC) reaction was used to create crosslinked polymeric networks with a predetermined and tunable excess of thiol or ene functionality. These materials rely on the use of readily available commercial monomers. By adopting standard molding techniques and simple TEC surface modifications, patterned surfaces with tunable hydrophobicity could be obtained. Moreover, these materials are shown to have great potential for rapid prototyping of microfluidic devices. In the second case, dendritic polymer scaffolds were evaluated for their ability to increase surface interactions and produce functional 3D networks. More specifically, a self-assembled dendritic monolayer approach was explored for producing highly functional dendronized surfaces with specific interactions towards pathogenic E. coli bacteria. Furthermore, a library of heterofunctional dendritic scaffolds, with a controllable and exact number of dual-purpose azide and ene functional groups, has been synthesized. These scaffolds were explored for the production of cell interactive hydrogels and primers for bone adhesive implants. Dendritic hydrogels decorated with a selection of bio-relevant moieties and with Young’s moduli in the same range as several body tissues could be produced by facile UV-induced TEC crosslinking. These gels showed low cytotoxic response and relatively rapid rates of degradation when cultured with normal human dermal fibroblast cells. When used as primers for bone adhesive patches, heterofunctional dendrimers with high azide-group content led to a significant increase in the adhesion between a UV-cured hydrophobic matrix and the wet bone surface (compared to patches without primers).

  • 880.
    Östmark, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Tuning Properties of Surfaces and Nanoscopic Objects using Dendronization and Controlled Polymerizations2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In this study, dendronization and grafting via controlled polymerization techniques, atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP), have been explored. Modification of surfaces and cellulose using these techniques, which enable grafting of well-defined polymer architectures, has been investigated. The interest in using cellulose stems from its renewability, biocompatibility, high molecular weight, and versatile functionalization possibilities.

    Dendronization was performed using disulfide-cored didendrons of 2,2-bis(methylol)propionic acid (bis-MPA) on gold surfaces, for the formation of self-assembled monolayers. It was found that the height of the monolayer increased with increasing dendron generation and that the end-group functionality controlled the wettability of the modified surface.

    Superhydrophobic cellulose surfaces could be obtained when a ‘graft-on-graft’ architecture was obtained using ATRP from filter paper after subsequent post-functionalized using a perfluorinated compound. The low wettability could be explained by a combination of a high surface roughness and the chemical composition.

    Biobased dendronized polymers were synthesized through the ‘attach to’ route employing dendronization of soluble cellulose, in the form of hydroxypropyl cellulose (HPC). The dendronized polymers were studied as nanosized objects using atomic force microscopy (AFM) and it was found that the dendron end-group functionality had a large effect on the molecular conformation on surfaces of spun cast molecules.

    ATRP of vinyl monomers was conducted from an initiator-functionalized HPC and an initiator-functionalized first generation dendron, which was attached to HPC. The produced comb polymers showed high molecular weight and their sizes could be estimated via AFM of spun cast molecules on mica and from dynamic light scattering in solution, to around 100-200 nm. The comb polymers formed isoporous membranes, exhibiting pores of a few micrometers, when drop cast from a volatile solvent in a humid environment. HPC was also used to initiate ROP of ε-caprolactone, which was chain extended using ATRP to achieve amphiphilic comb block copolymers. These polymers could be suspended in water, cross-linked and were able to solubilize a hydrophobic compound.

  • 881.
    Östmark, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Harrisson, Simon
    Center for Materials Innovation, Department of Chemistry, Washington University in Saint Louis.
    Wooley, Karen L.
    Center for Materials Innovation, Department of Chemistry, Washington University in Saint Louis.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Comb Polymers Prepared by ATRP from Hydroxypropyl Cellulose2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 4, p. 1138-1148Article in journal (Refereed)
    Abstract [en]

    Hydroxypropyl cellulose (HPC) was used as a core molecule for controlled grafting of monomers by ATRP, the aim being to produce densely grafted comb polymers. HPC was either allowed to react with an ATRP initiator or the first generation initiator-functionalized 2,2-bis(methylol)propionic acid dendron to create macroinitiators having high degrees of functionality. The macroinitiators were then "grafted from" using ATRP of methyl methacrylate (MMA) or hexadecyl methacrylate. Block copolymers were obtained by chain extending PMMA-grafted HPCs via the ATRP of tert-butyl acrylate. Subsequent selective acidolysis of the tert-butyl ester moieties was performed to form a block of poly(acrylic acid) resulting in amphiphilic block copolymer grafts. The graft copolymers were characterized by H-1 NMR and FT-IR spectroscopies, DSC, TGA, rheological measurements, DLS, and tapping mode AFM on samples spin coated upon mica. It was found that the comb (co)polymers were in the nanometer size range and that the dendronization had an interesting effect on the rheological properties.

  • 882.
    Östmark, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindqvist, Josefina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nyström, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Dendronized Hydroxypropyl Cellulose: Synthesis and Characterization of Biobased Nanoobjects2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 12, p. 3815-3822Article in journal (Refereed)
    Abstract [en]

    Dendronized polymers containing a cellulose backbone have been synthesized with the aim of producing complex molecules with versatile functionalization possibilites and high molecular weight from biobased starting materials. The dendronized polymers were built by attaching premade acetonide-protected 2,2-bis(methylol)propionic acid functional dendrons of generation one to three to a hydroxypropyl cellulose backbone. Deprotection or functionalization of the end groups of the first generation dendronized polymer to hydroxyl groups and long alkyl chains was performed, respectively. The chemical structures of the dendronized polymers were confirmed through analysis using H-1 NMR and FT-IR spectroscopies. From SEC analysis, the dendronized polymers were found to have an increasing polystyrene-equivalent molecular weight up to the second generation (M-n = 50 kg mol(-1)), whereas the polystyrene-equivalent molecular weight for the third generation was lower than for the second, although the same grafting density was obtained from H-1 NMR spectroscopy for the second and third generations. Tapping-mode atomic force microscopy was used to characterize the properties of the dendronized polymers in the dry state, exploring both the effect of the polar substrate mica and the less polar substrate highly oriented pyrolytic graphite (HOPG). It was found that the molecules were in the size range of tens of nanometers and that they were apt to undertake a more elongated conformation on the HOPG surfaces when long alkyl chains were attached as the dendron end-groups.

  • 883.
    Östmark, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Macakova, Lubica
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Auletta, Tommaso
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dendritic Structures Based on Bis(hydroxymethyl)propionic Acid as Platforms for Surface Reactions2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 10, p. 4512-4519Article in journal (Refereed)
    Abstract [en]

    In this paper we present results related to the self-assembly of different generations of disulfide-cored 2,2-bis(hydroxymethyl)propionic acid-based dendritic structures onto gold surfaces. These molecular architectures, ranging from generation 1 to generation 3, contain removable acetonide protecting groups at their periphery that are accessible for hydrolysis with subsequent formation of OH-terminated surface-attached dendrons. The deprotection has been investigated in detail as a versatile approach to accomplish reactive surface platforms. A special focus has been devoted to the comparison of the properties of the layers formed by hydrolysis of the acetonide moieties directly on the surface and in solution, prior to the layer formation.

  • 884.
    Östmark, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nyström, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Unimolecular Nanocontainers Prepared by ROP and Subsequent ATRP from Hydroxypropylcellulose2008In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 41, no 12, p. 4405-4415Article in journal (Refereed)
    Abstract [en]

    Hydroxypropylcellulose (HPC) is used as a macroinitiator for ring-opening polymerization of epsilon-caprolactone for the synthesis of a high molecular weight comb polymer consisting of a cellulose backbone and PCL grafts. The PCL end groups are converted into initiating sites for ATRP and chain extension of the PCL block is performed through grafting of tert-butyl acrylate to different lengths. The comb block copolymers are thereafter converted to amphiphilic polymers through deprotection of the tert-butyl group by acidic treatment, resulting in PCL-block-PAA grafts. These block copolymers are suspended in water and cross-linked using a water-soluble diamine to different attempted cross-link densities. Initial studies of the solubilization and encapsulation capacities of the amphiphilic polymers are performed using the hydrophobic model compound pyrene.

15161718 851 - 884 of 884
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf