Endre søk
Begrens søket
13141516 751 - 789 of 789
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 751.
    Yang, Ting
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Mechanical and swelling properties of hydrogels2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Hydrogels have been used as one of the novel soft materials in many biomedical applications such as drug delivery and tissue engineering for recent decades.

    In the main part of this work, bi-functional poly(ethylene glycol) (PEG) precursors with either thiols (PEG-SH) or allyls (PEG-Al) , covering molecular weights from 3 kDa to 8 kDa were synthesized and thoroughly characterized by 1H NMR, 13C NMR, FT-Raman and MALDI-TOF techniques. By combining PEG precursors with complementary trifunctional crosslinkers, a library of well-defined single-network hydrogels was efficiently constructed via the robust UV-initiated thiol-ene coupling (TEC) chemistry. Novel sequential interpenetrating network (seqIPN) hydrogels based on PEG were fabricated by diffusing and afterwards crosslinking secondary-network precursors within dense (2 kDa) to loose (8 kDa) primary networks. The impacts of polymer chain length and diffusion time on the swelling and mechanical properties were assessed for the seqIPN hydrogels. Additionally, disperse red 13 decorated PEG 2 kDa and 8 kDa were synthesized and used as probes to monitor the secondary-network precursor diffusion rate by UV/Vis spectroscopy. 

    FT-Raman and leaching tests were conducted to evaluate the efficiency of the TEC reaction for the development of PEG networks and their gel fractions. All gels were fully crosslinked within 5 minutes and with the gel fraction above 84%. The chain length of PEG, location of functional groups of PEGs, solvents, solid content were found to have directly influence on the mechanical and swelling properties of PEG single-network hydrogels. The utilization of the diffusion time dependent seqIPN strategy enabled further freedom to control the swelling and mechanical properties of PEG hydrogels, with the degree of water swelling ranged from 280 – 870% and the tensile modulus ranging from 1135 kPa to 175 kPa.

    Furthermore, the seqIPN strategy was utilized for fiber reinforced free radical polymerized hydrogels. N, N-dimethylacrylamide (DMA) with crosslinker poly(ethylene glycol) diacrylate were diffused in bacterial cellulose (BC) aerogel thereafter UV crosslinked to form BC-DMA hydrogels. FT-Raman and leaching tests were conducted to evaluate the efficiency of the free radical polymerization and the BC-DMA gel fractions. After UV cure for 10 minutes, robust DMA networks were formed within BC aerogels with over 94% gel fraction. The high porosity and robust interpenetrating DMA network within BC fibers were further analysed with FE-SEM. Compression tests showed that fiber reinforced DMA hydrogels have higher compression modulus than DMA hydrogels, ranging from 4.4 to 8.3 MPa with water content from 78 to 70%.

  • 752.
    Yang, Ting
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Mechanical properties of N, N-dimethylacrylamide hydrogels reinforced with bacterial cellulose aerogelManuskript (preprint) (Annet vitenskapelig)
  • 753.
    Yang, Ting
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Long, Hui
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gamstedt, E. Kristofer
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Characterization of Well-Defined Poly(ethylene glycol) Hydrogels Prepared by Thiol-ene Chemistry2011Inngår i: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 49, nr 18, s. 4044-4054Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Considering the large number of applications for hydrogels, a better understanding of the relation between molecular structure and mechanical properties for well-defined hydrogel is essential. A new library has been compiled of poly(ethylene glycol) polymers (PEG) of different length end functionalized with diallyl, dithiol, and dimethacrylate, and crosslinked with complementary trifunctional crosslinkers. In this study, the hydrogels were initially analyzed by FT-Raman and NMR to study the conversion ratio of the functional groups. The effects of solvent type, solid content concentration, curing time and length of the PEG chains on the final leaching, swelling and tensile properties of the hydrogels were studied.

  • 754.
    Yang, Ting
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Sequential interpenetrating poly(ethylene glycol) hydrogels prepared by UV-initiated thiol–ene coupling chemistry2013Inngår i: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 51, nr 2, s. 363-371Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Poly(ethylene glycol) (PEG)-diallyls, ranging from 2 to 8 kDa, were successfully reacted with a trifunctional thiol crosslinker via thiol–ene coupling reaction to construct four different primary PEG hydrogels. These systems were used as scaffolds for the preparation of a library of sequential interpenetrating networks (SeqIPNs). The solid content of the secondary networks varied between 21 and 34% and was dependent on the length of the absorbing PEGs. The gel fractions for the IPNs were above 85%. Additionally, the lowest degree of swelling was found for the IPN based on 2-kDa PEG (315%), whereas the 8-kDa PEG IPN exhibited a value of 810%. The SeqIPN strategy facilitated hydrogel systems that cover a larger domain of tensile modulus (192–889 kPa) when compared with single hydrogel networks (175–555 kPa).

  • 755.
    Yang, Ting
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    The influence of diffusion time on the properties of sequential interpenetrating PEG hydrogels2013Inngår i: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 51, nr 6, s. 1378-1386Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Four sets comprising a total of 16 sequential interpenetrating network (SeqIPN) hydrogels were efficiently fabricated via UV initiated thiol-ene coupling chemistry and from 2 kDa or 8 kDa primary poly(ethylene glycol) (PEG) networks (S2 and S8). Each primary system delivered four different SeqIPNs constructed after 2, 4, 20, and 44 h diffusion of secondary network PEG precursors, 2 kDa and 8 kDa. This allowed the assessment of both mechanical and swelling properties for a wide range of novel hydrogels ranging from loosely crosslinked SeqIPN 8-8 to densely crosslinked SeqIPN 2-2 systems. All gel fractions of secondary networks were above 83% and 44 h of diffusion was found sufficient to fully saturate the primary networks. Disperse red functionalized PEGs (2 kDa and 8 kDa) were further used as probes to investigate the diffusion mechanisms. The impact of diffusion time on loosely crosslinked S8 network with a swelling degree of 970% and tensile modulus of 175 kPa displayed a significant change in the final properties. For instance, a 2 h diffusion of 2 kDa PEG precursors generated a SeqIPN 8-2:2 comprising a secondary network solid content of 34% with a water swelling degree 580% and a tensile modulus of 365 kPa. On saturation, that is, 44 h of diffusion, SeqIPN 2-8:44 exhibited 64% of secondary network solid content, a swelling capacity of 380% and over fourfold of tensile modulus (758 kPa) when compared with the primary network S8. SeqIPN hydrogel with the highest tensile modulus and lowest degree of water swelling was obtained after 44 h diffusion of 2 kDa PEG precursors within the densely crosslinked S2 primary network. In this case, SeqIPN 2-2:44 noted a water swelling capability of 280% and a tensile modulus over 1 MPa. The latter was twofold when compared with S2 with a tensile modulus of 555 kPa. Consequently, the diffusion time of secondary network is a promising parameter to control and that enables the fabrication of PEG hydrogels with a wider window of mechanical and swelling properties.

  • 756.
    Yang, Xi
    KTH, Skolan för kemivetenskap (CHE).
    Polylactide and polycaprolactone grafted starch – synthesis, characterization and degradation2011Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Pollution is one of the most important issues in the world today. Renewable and degradable plastics attract more attention to the research. Starch can not only be used as food but also it has many other applications. In papermaking industry, textile, food processing, adhesive industry and some other areas, starch has its place.

    However starch-based materials show very poor mechanical properties due to their strong water absorption and poor interfacial adhesion with other components. This study aims to improve properties of starch-based materials. Starch granules surface were modified by lactic acid. Then polylactide and polycaprolactone were grafted on those surface modified starch granules. With the help of SEM, it was easy to notice that after grafting reactions, the smooth surface of starch granules became rough. However because of the purification process it was hard to calculate the grafting degree. Some films of starch, polylactide, polycaprolactone and grafted starch with different ratios were prepared and their properties and degradation behaviors were studied with DSC, Instron, SEM and FTIR. With PLA or PCL and surface grafting PLA or PCL in the matrix, water resistance of starch improved a lot. However maybe during the grafting process starch became more water soluble (gelatinized or amorphous) so water resistances of those films with grafted starch were less than those with raw starch granules. Films with grafted starch showed higher weight loss after degradation. The poor mechanical properties due to the severe phase separation between starch and PLA were, however, improved by grafting. It was also interest to find that films with 25% starch and 75% PCL showed good mechanical properties. The largest elongation at break and the largest tensile stress at tensile strength were shown by films with 25% st-g-PCL2 and 75%PCL.

  • 757.
    Yang, Xi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Strategies for Utilizing Biobased and Recycled Resources for Polylactide Plasticization2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    There are many aspects that should be considered to achieve truly "environmental friendly" and "sustainable" materials. These include the raw material resource, the energy consumption, the chemicals generated and used, the emissions during production, processing, transportation, disposal and so on. The work presented in this thesis focused on development of strategies for valorization of biopolymers and further utilization of the derived chemicals for plasticization of polylactide (PLA). This would retain the material value of the biopolymers, the degradability and biobased nature of PLA, while simultaneously broadening the application areas and properties of PLA.

    Two green, and efficient methodologies for chemical recycling of poly(3-hydroxybutyrate) (PHB), a natural biodegradable biopolymer produced in microorganisms as an energy storage material, were demonstrated. Full degradation to monomeric degradation products: crotonic acid (CA), 3-hydroxybutanoic acid (3HB) and 3-methoxybutanoic acid (3MB) was obtained in only 20 minutes through microwave assisted degradation in green solvents. Degradation parameters, such as solvent and basicity, were carefully evaluated for achieving high yield and fast degradation and the constituent ratio of degradation products could be tuned by adjusting the degradation time under the optimized condition. Meanwhile PHB oligomers with crotonic end groups (dPHB) were formed by thermal degradation of PHB during extrusion, which is an industrially viable process. The effects of degradation temperature and degradation time on the formation of degradation products were carefully adjusted, and the degradation kinetics at different temperatures were evaluated. Glucose, a depolymerization product of cellulose and starch, was modified by hexanoic acid to star shaped glucose esters (GHx) with different varying degrees of substitution by adjusting the reaction time.

    Two methodologies to plasticize PLA by utilizing the products from PHB recycling or the synthesized glucose esters were evaluated aiming at plasticizers with enhanced migration resistance compared to the physical blends or commercial analogues: 1) anchoring linear oligomeric plasticizers onto PLA and 2) blending low molar mass star shaped molecules into the PLA matrix. Specifically, PLA-CA-PBSA was prepared by coupling poly(butylene succinate-co-adipate) (PBSA) to CA functionalized PLA, PLA-g-dPHB was obtained by coupling dPHB onto the PLA main chain via reactive extrusion. PLA blends with star shaped GHx were also prepared. Decrease of Tg was observed for all the plasticized PLA samples. Blending GHx reduced the Tg of PLA by about 30 ºC and a decrease in Tg for approximately 25 ºC and 20 ºC was realized by coupling PLA with dPHB or PBSA, respectively. All plasticized PLA materials showed increased elongation at break. For PLA-g-dPHB a 66-fold increased elongation at break was achieved. The crystallization capacity of both PBSA and dPHB coupled PLA was improved at the same times as the PLA was plasticized. This is explained by the grafting points acting as nucleating sites and is further facilitated by the improved chain mobility of the PLA chains.

    The proposed approaches for PHB recycling, modification of glucose and the coupling or blending strategies demonstrated great promise for the concept of utilizing recycled biopolymers/biomass for plasticization of PLA.

  • 758.
    Yang, Xi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Migration resistant glucose esters as bioplasticizers for polylactide2015Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 132, nr 18, artikkel-id 41928Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Environmental and sustainability issues have catalyzed efforts to replace traditional polymer additives with biobased alternatives. Glucose pentaacetate (GPA) and sucrose octaacetate (SOA) as model commercial saccharide esters and three synthesized glucose hexanoate esters (GHs) were evaluated as bioplasticizers for polylactide (PLA). For the GHs different reaction times were utilized to reach plasticizers with different number of hexanoate groups to establish how the degree of substitution influences miscibility and migration resistance of the plasticizers. The synthesized GHs, GPA, and SOA all showed good miscibility with PLA. Largest improvements in strain at break were observed for the PLA films containing GH plasticizers. These films also exhibited simultaneous increase in stress at break as compared to plain PLA. The GH plasticizers had low tendency to migrate during aging in water and this migration resistance increased with increasing degree of substitution. The GHs are, thus, promising plasticizer alternatives for bioplastics as they also retain the biodegradable nature of these biobased materials.

  • 759.
    Yang, Xi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Microwave-Assisted Reaction in Green Solvents Recycles PHB to Functional Chemicals2014Inngår i: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 2, nr 9, s. 2198-2203Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An efficient microwave-assisted process for chemical recycling of poly(3-hydroxybutyrate) (PHB) in green solvents was demonstrated. Previously, PHB has been thermally recycled to crotonic acid and unsaturated oligomers. Our aim was to utilize green solvents (water, methanol, and ethanol) under alkaline conditions to achieve fast hydrolysis and monomeric or oligomeric degradation products with carboxyl and hydroxyl or methoxy or ethoxy end groups. Preliminary screening confirmed that the most efficient degradation process was obtained in alkaline methanol. In addition, sample amount, sodium hydroxide concentration, and degradation time all influenced the degradation process and final degree of degradation. Comparison with pure thermal degradation clearly demonstrated the effectiveness of the microwave-assisted process as the time and temperature needed for complete degradation was significantly reduced. Several characterization techniques were utilized for mapping the degradation processes and resulting degradation products. After optimization of the process, complete degradation of PHB to monomeric degradation products (3-hydroxybutanoic acid, 3-methoxybutanoic acid, and crotonic acid) was reached after only 20 min of microwave heating at 110 degrees C. Functional chemicals for synthesis or modification of biopolymers are thus obtainable from microwave-assisted degradation of PHB in green solvents. This offers new possibilities for retaining the material value of PHB via chemical recycling.

  • 760.
    Yang, Xi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Xu, Huan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Poly(lactide)-g-poly(butylene succinate-co-adipate) with High Crystallization Capacity and Migration Resistance2016Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 9, nr 5, artikkel-id 313Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Plasticized polylactide (PLA) with increased crystallization ability and prolonged life-span in practical applications due to the minimal plasticizer migration was prepared. Branched plasticized PLA was successfully obtained by coupling poly(butylene succinate-co-adipate) (PBSA) to crotonic acid (CA) functionalized PLA. The plasticization behavior of PBSA coupled PLA (PLA-CA-PBSA) and its counterpart PBSA blended PLA (PLA/PBSA) were fully elucidated. For both PLA-CA-PBSA and PLA/PBSA, a decrease of Tg to around room temperature and an increase in the elongation at break of PLA from 14% to 165% and 460%, respectively, were determined. The crystallinity was increased from 2.1% to 8.4% for PLA/PBSA and even more, to 10.6%, for PLA-CA-PBSA. Due to the inherent poor miscibility between the PBSA and PLA, phase separation occurred in the blend, while PLA-CA-PBSA showed no phase separation which, together with the higher crystallinity, led to better oxygen barrier properties compared to neat PLA and PLA/PBSA. A higher resistance to migration during hydrolytic degradation for the PLA-CA-PBSA compared to the PLA/PBSA indicated that the plasticization effect of PBSA in the coupled material would be retained for a longer time period.

  • 761. Yassin, Mohammed A.
    et al.
    Mustafa, Kamal
    Xing, Zhe
    Sun, Yang
    Fasmer, Kristine Eldevik
    Waag, Thilo
    Krueger, Anke
    Steinmueller-Nethl, Doris
    Wistrand, Anna Finne
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Leknes, Knut N.
    A Copolymer Scaffold Functionalized with Nanodiamond Particles Enhances Osteogenic Metabolic Activity and Bone Regeneration2017Inngår i: Macromolecular Bioscience, ISSN 1616-5187, E-ISSN 1616-5195, Vol. 17, nr 6, artikkel-id 1600427Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Functionalizing polymer scaffolds with nanodiamond particles (nDPs) has pronounced effect on the surface properties, such as improved wettability, an increased active area and binding sites for cellular attachment and adhesion, and increased ability to immobilize biomolecules by physical adsorption. This study aims to evaluate the effect of poly(l-lactide-co-e-caprolactone) (poly(LLA-co-CL)) scaffolds, functionalized with nDPs, on bone regeneration in a rat calvarial critical size defect. Poly(LLA-co-CL) scaffolds functionalized with nDPs are also compared with pristine scaffolds with reference to albumin adsorption and seeding efficiency of bone marrow stromal cells (BMSCs). Compared with pristine scaffolds, the experimental scaffolds exhibit a reduction in albumin adsorption and a significant increase in the seeding efficiency of BMSCs (p = 0.027). In the calvarial defects implanted with BMSC-seeded poly(LLA-co-CL)/ nDPs scaffolds, live imaging at 12 weeks discloses a significant increase in osteogenic metabolic activity (p = 0.016). Microcomputed tomography, confirmed by histological data, reveals a substantial increase in bone volume (p = 0.021). The results show that compared with conventional poly(LLA-co-CL) scaffolds those functionalized with nDPs promote osteogenic metabolic activity and mineralization capacity. It is concluded that poly(LLA-co-CL) composite matrices functionalized with nDPs enhance osteoconductivity and therefore warrant further study as potential scaffolding material for bone tissue engineering.

  • 762.
    Ye, Xinchen
    KTH, Skolan för kemivetenskap (CHE).
    Nanocomposites Based on Whey Protein Nano-Fibrils and Matrix2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The inclusion of nanoparticles has opened new possibilities to enhance and tune the properties of biobased materials. We here explored an approach to create protein homo-nanocomposites in which the nanoparticles and matrix are made from the same raw material. Whey protein isolate, as the raw material, are known to self-assemble into highly ordered nanofibrils under certain conditions. 2.5 - 15 % of protein nanofi brils solution was mixed with non-fibrillar matrix and 33 % glycerol as plasticizer. Tensile tests indicated increased elastic modulus and decreased  maximal elongation as function of increasing amounts of nanofibrils. The ultimate strength was less affected. It can be explained by the growth of  strongly  hydrogen-bonded peptide group in P-s heets observed by  IR  spectroscopy.  The  undulating  surface  and exifoliated P-sheets a lso have influence on the mechanical properties of the films.  Taken together, our study shows that it is possible to control the mechanical properties  of protein­  based materials  by addition  of protein nanofibrils.

  • 763.
    Yin, Bo
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Functional PVC Additives: Core-Shell Nanoparticle and Renewable Resource Plasticizers2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Several functional poly(vinyl chloride) (PVC) additives were designed: PVC plasticizers made from renewable resources as alternatives to traditional phthalate plasticizers and core-shell nanoparticle-plasticizers with the aim to design an additive that can improve several mechanical properties simultaneously. Monomeric and oligomeric PVC plasticizers based of isosorbide and glucose were synthesized. Their structures and molecular weights were determined by SEC, NMR, FTIR and LDI-MS. PVC was blended with the different plasticizers and miscibility, mechanical properties and thermal properties of the blends were analyzed. PVC/isosorbide dihexanoate (SDH) films exhibited similar properties as PVC/diisooctyl phthalate (DIOP) blends. PVC films plasticized by oligo(isosorbide suberate) (OSS) and oligo(isosorbide adipate) (OSA) showed better thermal stability and higher mechanical strength, but lower strain compared to the PVC/DIOP and PVC/SDH blends. Glucose ester plasticizers with slightly different chemical structures were synthesized by applying different reaction times. Results revealed that the plasticization efficiency was improved by larger number of hexanoate units on the glucose ring. Altogether the glucose esters showed great potential as renewable PVC plasticizers.

    Core-shell nanoparticle-plasticizers were designed with the aim to simultaneously improve both the stiffness and toughness of the materials. Halloysite, kaolin and silicon dioxide nanoparticles were surface-grafted by poly(butylene adipate) (PBA). The surface-grafting was confirmed by FTIR and the amount of grafting was determined by TGA. PVC/nanoparticles binary blends and PVC/PBA/nanoparticle ternary blends were prepared by solution casting. The dispersion of nanoparticles in the PVC matrix, as observed by SEM, was remarkably improved by the surface-grafting. The tensile stress at break for the PVC films containing 5 wt-% surface-treated halloysite nanoparticles (St-Halloy-5) increased 15 % compared with the material containing same amount of untreated halloysite nanoparticles (untreated Halloy-5) films. The St-Halloy-5 films also exhibited 30 times higher strain at break values compared to untreated Halloy-5 films. The PVC films containing 5 wt-% surface-treated silicon dioxide nanoparticles (St-SiO2-5) exhibited remarkably higher strain at break values even though the strength was slightly lower compared to the material with same amount untreated SiO2 particles. The nanoparticle surface treatment also improved the mechanical properties of PVC/PBA/nanoparticle ternary blends. PBA/St-Halloy exhibited most obvious improvement compared to PBA/Halloy, the values increased more than 100% for both stress at break and strain at break The results show that the designed nanoparticle-plasticizers could simultaneous improve the stiffness and toughness of PVC materials.

  • 764.
    Yin, Bo
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Aminlashgari, Nina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Glucose based green PVC plasticizersManuskript (preprint) (Annet vitenskapelig)
  • 765.
    Yin, Bo
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Core-shell nanoparticle-plasticizers for design of high-performance polymeric materials with improved stiffness and toughness2011Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, nr 24, s. 8670-8677Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 766.
    Yin, Bo
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Flexible and strong ternary blends of poly(vinyl chloride), poly(butylene adipate)and nanoparticle-plasticizers2013Inngår i: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 139, nr 2-3, s. 734-740Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multiple property enhancement was achieved for ternary blends of PVC, poly(butylene adipate) (PBA) plasticizer and PBA-grafted nanofillers as compared to ternary blends with untreated nanofillers. The blends with surface modified halloysite, kaolin or silicon dioxide nanofillers all exhibited higher stress at break and higher strain at break as compared to the corresponding composites with untreated nanoparticles. The strain at break was similar or improved compared to binary PVC/PBA blends. Most significant improvement was observed for the films containing surface treated halloysite nanofillers. Over 100% increase in stress at break and strain at break was obtained when compared to the corresponding nanocomposite containing untreated halloysite fillers. In addition to tensile testing the prepared films were characterized by DSC, SEM, TGA and FTIR imaging to evaluate the miscibility and thermal properties. Interestingly the FTIR imaging analysis revealed that the surface grafting of halloysite resulted not only in improved dispersion of halloysite filler, but also in more homogenous distribution of PBA plasticizer in the blends. During aging in contact with aqueous solution the films containing kaolin exhibited the smallest weight loss. This is explained by the plate like structure of kaolin which prevents the migration of PBA molecules.

  • 767.
    Yin, Bo
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Green Plasticizers from Liquefied Wood2014Inngår i: Waste and Biomass Valorization, ISSN 1877-2641, E-ISSN 1877-265X, Vol. 5, nr 4, s. 651-659Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Green plasticizers were designed from liquefied wood flour, a non-edible biobased waste product. Wood flour was liquefied to low molecular weight polyols by acid catalyzed reaction. The resulting polyol mixture, including the remaining liquefaction solvents glycerol and diethylene glycol, was further utilized for the synthesis of low molecular weight ester plasticizers. Monomeric (MLWP) and oligomeric (OLWP) plasticizers were prepared by esterification of the polyols by hexanoic acid or a mixture of hexanoic and adipic acid, respectively. Liquefied wood polyol mixture and the synthesized plasticizers were characterized by size exclusion chromatography, electrospray ionization-mass spectrometry and fourier transform infrared spectroscopy. MLWP, OLWP and traditional dioctyl phthalate (DIOP) plasticizer were blended with poly(vinyl chloride) (PVC) and tensile testing was performed to evaluate the plasticizing efficiency of the new plasticizers. In addition PVC blends containing model disaccharide ester, sucrose octaacetate (SOA), were prepared and tested. Highest strain at break was obtained after addition of SOA ester, which clearly shows the potential of sugar esters as PVC plasticizers. Addition of MLWP also resulted in slightly higher strain at break as compared to films plasticized with same amount of phthalate plasticizer, DIOP. Differential scanning calorimetry showed one concentration dependent glass transition temperature for all the studied blends indicating good miscibility. Our novel plasticizers are attractive environmentally friendly alternatives for phthalate plasticizers and could be prepared from biomass waste from agriculture and forest industry.

  • 768.
    Yin, Bo
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Oligomeric Isosorbide Esters as Alternative Renewable Resource Plasticizers for PVC2011Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 119, nr 4, s. 2400-2407Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 769.
    Yu, Wenbin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Reitberger, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hjertberg, T.
    Oderkerk, J.
    Costa, F. R.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Antioxidant consumption in squalane and polyethylene exposed to chlorinated aqueous media2012Inngår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, nr 11, s. 2370-2377Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Squalane stabilized with 0.2 wt.% of Irganox 1010 and a medium-density polyethylene containing 0.1 wt.% of the same antioxidant were exposed to two different aqueous media (water solutions containing either 10 ppm Cl-2 or 10 ppm ClO2, both buffered to pH = 6.8) at different temperatures between 30 and 70 degrees C. The squalane phase was characterized by differential scanning calorimetry (oxidation induction time, OIT) and infrared spectroscopy, and the aqueous media were analysed after concentrating the analytes using liquid-liquid extraction by liquid chromatography, mass spectrometry and infrared spectroscopy. OIT measurements were carried out on the polyethylene samples after exposure to the chlorinated aqueous media. Exposure of the squalane systems to water containing ClO2 resulted in discolouration by the formation of quinoid structures and a faster depletion of the antioxidant than exposure to water containing Cl-2. The activation energy for the loss of antioxidant activity on exposure to ClO2-water was very low (<10 kJ mol(-1)) in the squalane test (no diffusion control) and 21 +/- 2 kJ mol(-1) at a depth of 1-2 mm from the surface of polyethylene plaques (diffusion control). Calculation from earlier published OIT data from a HDPE exposed to Cl-2-water yielded an activation energy for the loss antioxidant activity of 68 kJ mol(-1). The antioxidant degradation products obtained from the exposure to the ClO2 aqueous medium were found at a higher concentration, were more polar and exhibited a higher proportion of low molar mass species than those obtained after exposure to the Cl-2 aqueous medium. The important chemical difference between ClO2 and Cl-2 is that the former is a one-electron oxidant whereas the latter preferentially reacts by hydrogen substitution. Possible further reactions, in agreement with the observations made, are proposed.

  • 770. Yurindatama, D.
    et al.
    Barsoum, Imad
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner. The Petroleum Institute, United Arab Emirates.
    Constitutive model and failure locus of a polypropylene grade used in offshore intake pipes2017Inngår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 57, s. 245-259Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BorECO®™ BA212E is a polypropylene block co-polymer which has become a common material in the manufacturing of large diameter non-pressurized gravity offshore intake pipelines. These lines are used for transportation of sea water for cooling of petrochemical process plants. The pipe sections are joined by butt heat fusion welding to create the pipeline. Recently a few premature failures of such pipelines have been reported in the field. Hence, there is a need to characterize the constitutive behavior of the pipe and weld material in order to properly design these pipes. The aim of this work is to determine the material constitutive behaviors of the pipe material and the welded joint material. Uniaxial tensile tests of both the pipe and weld joint material are conducted at various strain rates. Both the pipe and weld material show a rather high strain rate dependency, with the weld material having about half the yield strength than that of the pipe material. An analytical constitutive material model is developed for both the pipe and weld material, incorporating the effect of strain rate. The failure locus, expressed in terms of the equivalent plastic strain at failure vs. the stress triaxiality, for both materials is also determined as part of the constitutive model using notched dumbbell specimens. The constitutive model and failure loci for the pipe and weld material are implemented in a finite element model (FEM) and are validated by conducting a series of independent four-point bend experiments on both material types. The validation is carried out by comparing the FEM results of the four-point bend model with the experimental results, which show a rather good agreement.

  • 771. Zhang, Junqiao
    et al.
    Li, Debing
    Sun, Tianyang
    Liang, Lijun
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi. Zhejiang University, China.
    Wang, Qi
    Interaction of P-glycoprotein with anti-tumor drugs: the site, gate and pathway2015Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 11, nr 33, s. 6633-6641Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding the mechanism and pathway of anti-cancer drugs to be pumped out by P-glycoprotein (P-gp) in cancer cell is very important for the successful chemotherapy. P-gp is a member of ATP-binding cassette (ABC) transporters. In this study, random accelerated molecular dynamics (RAMD) simulation was used to explore the potential egress pathway of ligands from the binding pocket. This could be considered as a reverse process of drug binding. The most possible portal of drugs to dissociate is TM4/TM6, which is almost the same for different drugs, such as paclitaxel and doxorubicin. The interactions in the binding site are found to be remarkably stronger than that outside of the binding site. The results were suggested by the free energy calculation between P-gp and different drugs from metadynamics simulation. All the results indicate that the flexibility of inner residues, especially the residue Phe339, is very important for the drugs to access the binding site.

  • 772.
    Zhang, Le
    KTH, Skolan för kemivetenskap (CHE).
    Large Scale Production of Polylactide Microspheres for Controlled Drug Delivery2012Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Spray drying is presented as an efficient technique to manufacture spherical polylactide particles in large scale for use in controlled drug delivery applications. Poly (L-lactide) (PLLA) was synthesized by ring-opening polymerization and PLLA microspheres were produced by spray drying. The PLLA microspheres were morphologically characterized by SEM and the release profile of drug loaded in the microspheres were analyzed by UV-VIS. The morphology of PLLA microspheres was significantly influenced by solvent, molecular weight, and the operating settings of the instrument.

    PLLA particles loaded with diclofenac sodium and caffeine were produced using the 10,000 and 20,000 g/mol molecular weight PLLAs and the previously determined operating conditions. The morphologies of particles loaded with drug were influenced by solvent type. The drug encapsulation efficiency of caffeine was much higher than that of diclofenac sodium.

    The release rate was affected by the type of drug loaded and the particle morphology. Particles of small size released drug faster because of larger surface area and particles with a rough surface and high porosity also demonstrated an increased drug release rate. All loaded diclofenac sodium was released from the particles after 400 hours whereas only 30-50% of the loaded caffeine was released during the same time period.

  • 773. Zhang, M.
    et al.
    Wang, R.
    Xiang, T.
    Zhao, Wei-Feng
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi. Sichuan University, China.
    Zhao, C. -S
    Preparation, characterization and application of poly(sodium p-styrenesulfonate)/poly(methyl methacrylate) particles2016Inngår i: Journal of Industrial and Engineering Chemistry, ISSN 1226-086X, E-ISSN 1876-794X, Vol. 34, s. 415-421Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, poly(sodium p-styrenesulfonate)/poly(methyl methacrylate) particles were facilely prepared by in situ cross-linked polymerization followed with a liquid-liquid phase inversion technique. The particles exhibited selective adsorption for cationic dyes due to the negatively charged sulfonic groups. The intra-particle diffusion process was the rate-limiting step for the adsorption of methylene blue. More than 90% of cationic dye was removed by the adsorption column of the particles after three circulations. The particles could be facilely fabricated and industrially used for wastewater treatment.

  • 774. Zhang, Man
    et al.
    Wang, Rui
    Shi, Zhenqiang
    Huang, Xuelian
    Zhao, Weifeng
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Zhao, Changsheng
    Multi-responsive, tough and reversible hydrogels with tunable swelling property2017Inngår i: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 322, s. 499-507Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel family of multi-responsive, tough, and reversible hydrogels were prepared by the combination of dipole-dipole interaction, hydrogen bonding interaction and slightly chemical cross-linking, using monomers of acrylonitrile, sodium allylsulfonate and itaconic acid. Reversible gel-sol transition was achieved by the flexible conversion of the dipole-dipole interactions between acrylonitrile-acrylonitrile and acrylonitrile-sodium thiocyanate, and the hydrogels could freely form desired shapes. The dipole dipole and hydrogen bonding interactions improved the mechanical strength of the hydrogels with a compressive stress of 2.38 MPa. Meanwhile, the hydrogels sustained cyclic compressive tests with 60% strain, and exhibited excellent elastic property. The hydrogels were sensitive to pH and ionic strength, and could keep their perfect spherical structures without any obvious cracks even after immersing in strong ionic strength (or pH) solution for several reversible cycles. Furthermore, the hydrogels were recycled for environmental pollution remediation, and showed great potential to be applied in water treatments and other related fields.

  • 775.
    Zhao, Weifeng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi. Sichuan Univ, Peoples R China.
    Huang, Xuelian
    Wang, Yilin
    Sun, Shudong
    Zhao, Changsheng
    A recyclable and regenerable magnetic chitosan absorbent for dye uptake2016Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 150, s. 201-208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A recyclable and regenerable magnetic polysaccharide absorbent for methylene blue (MB) removal was prepared by coating magnetic polyethyleneimine nanoparticles (PEI@MNPs) with sulfonated chitosan (SCS) and further cross -linked with glutaraldehyde. The driving force for coating is the electrostactic interaction between positively charged PEI and negatively charged SCS. Infrared spectra, zeta potential, thermal gravimetric analysis and X-ray diffraction demonstrated the successful synthesis of magnetic polysaccharide absorbent. The self-assembly of polysaccharide with magnetic nanopartices did not alter the saturation magnetization value of the absorbent confirmed by vibrating sample magnetometer. The nanoparticles showed fast removal (about 30 min reached equilibrium) of MB. In particular, the removal ability of MB after desorption did not reduce, demonstrating an excellent regeneration ability. Our study provides new insights into utilizing polysaccharides for environmental remediation and creating advanced magnetic materials for various promising applications.

  • 776.
    Zhao, Weifeng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi. Sichuan University, China.
    Nugroho, Robertus Wahyu. N.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Zhao, Changsheng
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    In Situ Cross-Linking of Stimuli-Responsive Hemicellulose Microgels during Spray Drying2015Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, nr 7, s. 4202-4215Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chemical cross-linking during spray drying offers the potential for green fabrication of microgels with a rapid stimuli response and good blood compatibility and provides a platform for stimuli-responsive hemicellulose microgels (SRHMGs). The cross-linking reaction occurs rapidly in situ at elevated temperature during spray drying, enabling the production of microgels in a large scale within a few minutes. The SRHMGs with an average size range of similar to 1-4 mu m contain O-acetyl-galactoglucomannan as a matrix and poly(acrylic acid), aniline pentamer (AP), and iron as functional additives, which are responsive to external changes in pH, electrochemical stimuli, magnetic field, or dual-stimuli. The surface morphologies, chemical compositions, charge, pH, and mechanical properties of these smart microgels were evaluated using scanning electron microscopy, IR, zeta potential measurements, pH evaluation, and quantitative nanomechanical mapping, respectively. Different oxidation states were observed when AP was introduced, as confirmed by UV spectroscopy and cyclic voltammetry. Systematic blood compatibility evaluations revealed that the SRHMGs have good blood compatibility. This bottom-up strategy to synthesize SRHMGs enables a new route to the production of smart microgels for biomedical applications.

  • 777.
    Zhao, Weifeng
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. Sichuan University, China.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Zhao, Changsheng
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    In Situ Synthesis of Magnetic Field-Responsive Hemicellulose Hydrogels for Drug Delivery2015Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, nr 8, s. 2522-2528Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A one-pot synthetic methodology for fabricating stimuli-responsive hemicellulose-based hydrogels was developed that consists of the in situ formation of magnetic iron oxide (Fe3O4) nanoparticles during the covalent cross-linking of O-acetyl-galactoglucomannan (AcGGM). The Fe3O4 nanoparticle content controlled the thermal stability, macrostructure, swelling behavior, and magnetization of the hybrid hydrogels. In addition, the magnetic field-responsive hemicellulose hydrogels (MERHHs) exhibited excellent adsorption and controlled release profiles with bovine serum albumin (BSA) as the model drug. Therefore, the MFRHHs have great potential to be utilized in the biomedical field for tissue engineering applications, controlled drug delivery, and magnetically assisted bioseparation. Magnetic field-responsive hemicellulose hydrogels, prepared using a straightforward one-step process, expand the applications of biomass-derived polysaccharides by combining the renewability of hemicellulose and the magnetism of Fe3O4 nanoparticles.

  • 778.
    Zhao, Yadong
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Excellent chemical and material cellulose from tunicates: diversity in cellulose production yield and chemical and morphological structures from different tunicate species2014Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, nr 5, s. 3427-3441Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The high crystallinity and the high microfibrils aspect ratio of tunicate cellulose (TC) indicate TC's excellent chemical and material applications. However, its quantity and quality from different species have never been systematically reported and compared. In this study, the tunics of Ciona intestinalis (CI), Ascidia sp. (AS), Halocynthia roretzi (HR) and Styela plicata (SP) were processed to TC after an identical prehydrolysis-kraft cooking-bleaching sequence, while the tunicate fibrils were chemically and structurally characterized in situ and during the sequence. All tunics studied were composed of crystalline cellulose embedded with protein, lipids, sulfated glycans and mucopolysaccharides. The native composite structures are all very compact. However, the tunics from Phlebobranchia order (CI and AS) are soft, while those from Stolidobranchia, HR and SP, are hard. Fibrous cellulose could be prepared after removing the lipids, sulfated glycans and mucopolysaccharides through prehydrolysis, protein removal through kraft cooking and a final purification by bleaching. The final product is similar to 100 % pure cellulose which is in large molecular masses, composed of highly crystalline I-beta crystals, in elementary microfibrils form, with high specific surface area and thermal stability. There were lower TC yields from the soft tunics than from the hard ones. The cellulose fibrils had a section shape of lozenges with higher crystallinity. This study demonstrates that TC could be obtained in different yields and exhibited different chemical and morphological structures depending on the species. There is a great potential of tunicate resources for preparing excellent chemical and material cellulose.

  • 779.
    Zhao, Yadong
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Moser, Carl
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Transparent Composites Made from Tunicate Cellulose Membranes and Environmentally Friendly Polyester2018Inngår i: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 11, nr 10, s. 1728-1735Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of optically transparent composites were made by using tunicate cellulose membranes, in which the naturally organized cellulose microfibrillar network structure of tunicate tunics was preserved and used as the template and a solution of glycerol and citric acid at different molar ratios was used as the matrix. Polymerization through ester bond formation occurred at elevated temperatures without any catalyst, and water was released as the only byproduct. The obtained composites had a uniform and dense structure. Thus, the produced glycerol citrate polyester improved the transparency of the tunicate cellulose membrane while the cellulose membrane provided rigidity and strength to the prepared composite. The interaction between cellulose and polyester afforded the composites high thermal stability. Additionally, the composites were optically transparent and their shape, strength, and flexibility were adjustable by varying the formulation and reaction conditions. These composites of cellulose, glycerol, and citric acid are renewable and biocompatible and have many potential applications as structural materials in packaging, flexible displays, and solar cells.

  • 780.
    ZHAOXUAN, FENG
    KTH, Skolan för kemivetenskap (CHE).
    Synthesis and Characterization of Drug-Anchored Pluronic Micelles2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Amphiphilic Pluronic block copolymer consisting of hydrophobic poly(propylene oxide) (PPO) and hydrophilic poly(ethylene oxide) (PEO) blocks has sparked promising effect in the area of drug delivery systems due to specific advantages over other drug carriers such as 1) biocompatibility and nontoxicity 2) ability to encapsulate water-insoluble drugs 3) possibility to promote its functions by modification. However, a deadly weak point of Pluronic-based drug carriers depends on the relatively weak hydrophobic driving force coming from PPO core to stabilize amphiphilic micelles, which may lead to the micelle disintegration and sudden release of drug after being injected into the bloodstream. In this project, an optimized micelle system with cancerous cell-targeting functionality by conjugated folic acid at the chain end of Pluronic F127 (or L35) together with improved stability through chemical attachment of quercetin on the chain end of Pluronic 10R5 was developed. Data from a series of characterization techniques indicated that quercetin-anchored mixed micelle systems (FF/PQ and LF/PQ) were successfully formed. Folic acid (as a targeting ligand for tumor cells) decorated the surface of the micelles and anti-cancer drug was located in the core. Meanwhile, these mixed micelle system possessed optimized properties in terms of stability, PDI and size.

  • 781.
    Zhou, Qi
    et al.
    Wuhan University, China .
    Zhang, L. N.
    Wuhan University, China .
    Minoda, M.
    Wuhan University, China .
    Miyamoto, T.
    Wuhan University, China .
    Phase transition of thermosensitive amphiphilic cellulose esters bearing olig(oxyethylene)s2000Inngår i: Polymer Bulletin, ISSN 0170-0839, E-ISSN 1436-2449, Vol. 45, nr 05-apr, s. 381-388Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of cellulose esters bearing olig(oxyethylene)s with different degree of substitution (DS) and different length of the oxyethylene chain were synthesized by a homogeneous reaction of cellulose with corresponding monofunctional acid chloride in a 10% LiCl-dimethyl acetoamide (DMAc) solution. The effect of total DS value on the solubility of the derivatives in aqueous solution was investigated. It was found that the lower limit DS value for both water-soluble and amphiphilic derivatives decreases with increasing length of oxyethylene chains. The amphiphilic derivatives, which are soluble in both water and chloroform, precipitate out of aqueous solution on heating without gel forming, such a phase transition behavior was studied in terms of DS value, length of oxyethylene and concentration. The precipitation temperature (T-p) of the amphiphilic derivatives is range from 54 degreesC to 96 degreesC. It decreases with increasing the total DS value, and increases with an increase in the length of oxyethylene chains. The T-p value of the derivatives was found to be almost independent in the concentration range of 1-15 wt %, however the T-p value increases sharply with decreasing polymer concentration when the concentration is lower than 1 wt%.

  • 782.
    Zhu, Jiqing
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Birgisson, Björn
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Kringos, Niki
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Transportvetenskap, Väg- och banteknik.
    Polymer modification of bitumen: Advances and challenges2014Inngår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 54, nr 1, s. 18-38Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Advances and challenges in the field of bitumen polymer modification for road construction during the last 40 years are reviewed in this paper. The history of bitumen polymer modification is described chronologically. Some popular plastomers and thermoplastic elastomers in bitumen modification are discussed regarding their advantages and disadvantages, including polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate (EVA), ethylene-butyl acrylate (EBA), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS) and styrene-ethylene/butylene-styrene (SEBS). Although these polymers all improve bitumen properties to some extent, there are still some drawbacks limiting the future development of bitumen polymer modification, such as high cost, low ageing resistance and poor storage stability of polymer modified bitumen (PMB). Researchers attempted various ways to remove these drawbacks. Some technical developments for removing drawbacks are reviewed in this paper, including saturation, sulfur vulcanization, adding antioxidants, using hydrophobic clay minerals, functionalization and application of reactive polymers. The future development of polymers for bitumen modification is analyzed as well. Since it is currently challenging to perfectly achieve all expected PMB properties at the same time, some compromised recommendations are given in this paper, among which greatly enhancing the properties with an acceptably high cost, significantly reducing the cost with relatively poor properties and their combinations. Functionalization is emphasized as a promising way to enhance the properties of currently used polymers and develop new-type polymer modifiers with much greater success in the future. It is also recommended that future research on bitumen polymer modification focuses more on function development towards enhancing: adhesion with aggregates, long-term performance and recyclability.

  • 783. Zhu, Liangliang
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Sanders, Samuel N.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Unimolecular Photopolymerization of High-Emissive Materials on Cylindrical Self-Assemblies2015Inngår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 48, nr 15, s. 5099-5105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report a novel self-assembly pathway from a bis(imidazolyl) diphenyl-diacetylene (DPDA) compound as a realization of self-templated photopolymerization with high polymerization degrees. The work takes advantage of a cylindrical self-assembly that strengthens the preorganization of the diphenyl-diacetylene moiety at the single molecular level. On this basis, photopolymerization of DPDA can be conducted smoothly to form high-molecular-weight polydiphenyl diacetylene. Such a cylindrical self-assembly is highly dependent on molecular structure, and control studies show that only oligomers can be formed on random self-assemblies from a monoimidazolyl or nonimidazolyl diphenyl-diacetylene compound. Moreover, the cylindrical self-assembly based systems bear aggregation-induced emission enhancement characteristics and are solution processable. The leading thin-film could afford a selectively tunable function in luminescent micropatterns.

  • 784.
    Zhu Ryberg, Yingzhi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Wood hydrolysates- New concepts in renewable material design2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Wood hydrolysates (WHs) are biomasses obtained in processes involving hydrothermal treatments of wood. WHs are rich in hemicelluloses and lignin. Instead of complicated extraction processes, such as precipitation, or extensive purification, this work utilizes the crude WHs. These WHs were successfully developed into oxygen-barrier films and coatings and a conceptual model was established to predict biomass matrix performance from molecular structures and interactions.

    Free standing films and coatings from blends of WHs and either chitosan or carboxylmethyl cellulose (CMC) as a co-component, were produced. The films had an excellent oxygen-barrier performance which was even better than the corresponding films prepared from highly purified hemicelluloses. From a fundamental point of view, the Hansen solubility parameter (HSP) theory revealed the interactions between molecules in WHs, as well as in WH-based blends, which shed light on the great barrier performance of WH-based films. The hypothesis was that these strong interactions increased the mutual molecular affinity in the matrix, which led to a denser molecular packing and hence a good oxygen-barrier performance. The positron annihilation lifetime spectroscopy (PALS) measurements quantified the free volumes in the WH-based matrices. The HSP results, free volume size and distribution and thermal analyses supported the hypothesis well.

    The HSP model was then used as a tool for designing oxygen-barrier coatings from WH-based blends. Using the HSP model, the interactions between different WHs and CMC were calculated and quantified. According to our hypothesis, the oxygen-barrier performance could thus be predicted. The free volume from PALS, oxygen permeability (OP) results were generally in consistence with the prediction from HSP model, which shows the potential of the HSP model for designing formulations of WHs for oxygen-barrier coatings for food packaging. 

    To realize an industrially feasible and efficient process for WH-based barrier coating layers, some new approaches were attempted. Previously, coatings were prepared manually from WH-based blends. Now, a creative spray drying (SPD) coating technique was developed for a reproducible, efficient coating process of WHs with no additives or second components. Also, glyoxal crosslinking improved the ductility of the WH-based coatings which in turn improved the quality and oxygen-barrier performance of the coatings. Finally, scanning electron microscopy (SEM) integrated with a micro-tensile test device made it possible the real-time observation of coating surfaces during the deformation process. This can successfully analyze the mechanical performance of the coatings without being influenced by substrate.

    In summary, the WHs present a viable and very promising resource for green barrier design.

  • 785.
    Zhu Ryberg, Yingzhi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Innovative Approaches for Converting a Wood Hydrolysate to High-Quality Barrier Coatings2013Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, nr 16, s. 7748-7757Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An advanced approach for the efficient and controllable production of softwood hydrolysate-based coatings with excellent oxygen-barrier performance is presented. An innovative conversion of the spray-drying technique into a coating applicator process allowed for a fast and efficient coating process requiring solely aqueous solutions of softwood hydrolysate, even without additives. Compared to analogous coatings prepared by manual application, the spray-drying produced coatings were more homogeneous and smooth, and they adhered more strongly to the substrate. The addition of glyoxal to the aqueous softwood hydrolysate solutions prior to coating formation allowed for hemicellulose cross-linking, which improved both the mechanical integrity and the oxygen-barrier performance of the coatings. A real-time scanning electron microscopy imaging assessment of the tensile deformation of the coatings allowed for a deeper understanding of the ability of the coating layer itself to withstand stress as well as the coating-to-substrate adhesion.

  • 786. Zikeli, Florian
    et al.
    Ters, Thomas
    Fackler, Karin
    Srebotnik, Ewald
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Fractionation of wheat straw Dioxane lignin reveals molar mass dependent structural differences2016Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 91, s. 186-193Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dioxane lignin was isolated from ball-milled wheat straw by neutral dioxane-water extraction and subsequently molar-mass-fractionated by flash chromatography in dimethylformamide. The eluted lignin containing material was pooled into six distinct molar mass fractions that were in turn structurally characterized in detail by wet chemistry and NMR spectroscopy methods. Fractions of higher molar mass were found to be enriched in p-hydroxyphenyl units and contained more p-hydroxycinnamic acid units. They were found mainly associated with linear arabinoxylan, while in low-molar-mass fractions additional glucan contributions were found. Fractions of lower molar mass consisted of relatively more guaiacyl units and showed exclusive association with tricin units. One distinct lignin fraction with lower lignin content supposedly contained high ratios of arabinoxylan chains esterified by ferulic acid and cross-linked via ferulic acid dimerization, structures which were considered to represent lignin nucleation sites. High abundance of dibenzodioxocin type structures in this fraction indicated that they could be involved in cross-linking hemicelluloses networks with lignin moieties.

  • 787. Çakir, S.
    et al.
    Eriksson, Magnus
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Martinelle, Mats
    KTH, Skolan för bioteknologi (BIO), Industriell bioteknologi.
    Koning, C. E.
    Multiblock copolymers of polyamide 6 and diepoxy propylene adipate obtained by solid state polymerization2016Inngår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 79, s. 13-22Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyesteramide multiblock copolymers based on polyamide 6 and diepoxy propylene adipate blocks were synthesized. For this purpose a carboxyl-terminated polyamide 6 (Mn = 2400 g/mol, Tm = 205.5 °C) and diepoxy propylene adipate (Mn = 450 g/mol) were separately synthesized and characterized. The incorporation of the oligoester into the polyamide 6 backbone was performed by solid state polymerization (SSP) well below the melting temperature of the polyamide (80-140 °C) so that the physical and thermal properties of the original polyamide 6 block were retained. Formation of the multiblock structure was confirmed by following the increase in molecular weight by SEC, reaction of the end groups by 1H NMR and by following the maintained melting temperature after the copolymerization. These segmented copolymers have molecular weights up to 10 kg/mol, thermal stability of 325 °C at 5% weight loss and a melting temperature of 205 °C.

  • 788.
    Öberg Hed, Kim
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Advanced polymeric scaffolds for functional materials in biomedical applications2014Doktoravhandling, med artikler (Annet vitenskapelig)
    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).

  • 789.
    Öberg, Viktor
    KTH, Skolan för kemivetenskap (CHE).
    Macroalgae as a renewable resource: Extraction and Characterization of the Major Components in Saccharina Latissima2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A fractionation strategy was developed that made it possible to extract alginate, mannitol, laminarin and cellulose under various conditions from the brown algae Saccharina Latissima (previously known as Laminara Saccharina). The algae were harvested on the west coast of Sweden in the late summer of 2013. After extraction, the alginate and mannitol samples were identified and characterized using 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The yield of alginate (in its sodium salt form) was estimated to be around 18,5 %, and the yield of mannitol was around 9 %. Mild hydrolysis and 1H NMR was performed on the alginate to estimate the ratio of mannuronic and guluronic acids, i.e. the M/G-ratio. The M/G-ratio was calculated to be around 1 for neutral batches and around 1,1 for batches extracted at low or high pH. Laminarin was identified and characterized by 1H NMR, FT-IR, TGA, size exclusion chromatography (SEC) and ion chromatography (IC). Approximately 12 % laminarin was extracted. Cellulose was identified and characterized by FT-IR and IC, and the yield was approximately 2,5 to 3,5 %.

    A three-level statistical factorial screening of the parameters temperature and pH was also performed using multiple linear regression (MLR) from 6 responses: the alginate, laminarin, cellulose, mannitol and total yield as well as the M/G-ratio. However, the yields of alginate, cellulose and mannitol were not possible to assess due to divergent data points. High temperature (75 °C) and pH 2 or 12 degrades alginate, thus decreasing the yield. The screening of laminarin yield showed that a decrease in pH had a significant positive effect. The screening of total yield indicated a negative effect when temperature was increased from 40 °C to 75 °C. At 3 or 40 °C, the M/G-ratio was significantly lower at neutral pH compared to those at pH 2 or 12. At 75 °C and pH 12, a degradation decreased the M/G-ratio to 0,83.

13141516 751 - 789 of 789
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf