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  • 1.
    Hakkarainen, Minna
    et al.
    University of Helsinki, Finland.
    Jansson, Robert
    University of Helsinki, Finland.
    Sundholm, Francesca
    University of Helsinki, Finland.
    Liquid-Crystalline Behavior Of Some Carboxylic-Acids1993In: Polymer Bulletin, ISSN 0170-0839, E-ISSN 1436-2449, Vol. 31, no 1, p. 43-48Article in journal (Refereed)
    Abstract [en]

    A series of 4-omega-carboxyalkoxyphenyl-4'-methoxybenzoates 2 underbar has been prepared. Compounds with a spacer length of n=3 and n=5 show liquid crystalline behaviour. The products were characterized by IR and H-1NMR -spectroscopy, mass spectrometry, optical microscopy and DSC -measurements. The compounds are potentially useful as side-groups in liquid-crystalline polymers.

  • 2. Hu, Minggang
    et al.
    Wang, Mei
    Zhang, Peili
    Jin, Kun
    Chen, Yuee
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Polymerization of rac-lactide catalyzed by group 4 metal complexes containing chiral N atoms2012In: Polymer Bulletin, ISSN 0170-0839, E-ISSN 1436-2449, Vol. 68, no 7, p. 1789-1799Article in journal (Refereed)
    Abstract [en]

    The hydroxyl- and phenoxy-bridged dinuclear zirconium and hafnium complexes, 1 and 2, containing a chiral N atom in the N2O2 ligand (H2L = 2-(((2-pyridylmethyl)(2-hydroxyphenyl)amino)methyl)-4,6-di(tert-butyl)ph enol) were used as catalysts for the ring-opening polymerization of rac-lactide. Experiments prove that 1 and 2 are living and controlled catalytic systems with activity up to 3.25 g(pol) mmol(ini) (-1) h(-1). The isotactic-rich polylactides in a narrow polydispersity (M (w)/M (n) = 1.01-1.13) were produced with enantiomeric complexes 1 and 2 (P (m) = 0.65-0.73). The kinetic studies show a first-order dependency in both monomer and initiator. The initiation mechanism is discussed on the basis of the MALDI-TOF MS and H-1 NMR spectra of the rac-LA oligomer prepared by 1.

  • 3. Liu, X. H.
    et al.
    Wu, Q. J.
    Zhang, Q. X.
    Berglund, Lars A.
    Mo, Z. S.
    High-temperature X-ray diffraction studies on polyamide6/clay nanocomposites upon annealing2002In: Polymer Bulletin, ISSN 0170-0839, E-ISSN 1436-2449, Vol. 48, no 05-apr, p. 381-387Article in journal (Refereed)
    Abstract [en]

    The influence of nanodispersed clay on the alpha crystalline structure of polyamide 6 (PA6) was examined in-situ with X-ray diffraction (XRD) between room temperature and melting. In pure PA6 upon annealing the alpha crystalline phase was substituted by an unstable pseudohexagonal phase at 150degreesC, then it transformed into a new stable crystalline structure - high temperature alpha' phase above the transition temperature. However, in PA6/clay nanocomposite (PA6CN), the alpha phase did not present crystalline phase transition on heating. The increase in the annealing temperature only led to continuous intensity variation. The different behaviors were caused by the confined spaces formed by silicate layers, which constrained the mobility of the polymer chains in-between.

  • 4. Qu, X.
    et al.
    Wirsen, A.
    Olander, B.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Surface modification of high density polyethylene tubes by coating chitosan, chitosan hydrogel and heparin2001In: Polymer Bulletin, ISSN 0170-0839, E-ISSN 1436-2449, Vol. 46, no 03-feb, p. 223-229Article in journal (Refereed)
    Abstract [en]

    Chitosan and chitosan hydrogel were immobilized on both the inside and outside surfaces of high density polyethylene (HDPE) tubes with 2.5x4 mm diameters. First, acrylic acid was grafted on the surfaces of HDPE by electron beam (2.5 Mrad) preirradiation method. Then chitosan/HCl and chitosan/lactic acid solutions were coated on the modified hydrophilic HDPE surfaces, the latter could form a pH-sensitive hydrogel layer on the surfaces. The tube surfaces were further modified with heparin by surface interpenetrating method to improve blood compatibility. ATR-FTIR and ESCA methods were used to characterize the coated surfaces. The morphology changes were monitored by Scanning Electron Microscope (SEM).

  • 5.
    Zhou, Qi
    et al.
    KTH, School of Biotechnology (BIO), Glycoscience.
    Zhang, L. N.
    Li, M.
    Wu, X. J.
    Cheng, G. Z.
    Homogeneous hydroxyethylation of cellulose in NaOH/urea aqueous solution2005In: Polymer Bulletin, ISSN 0170-0839, E-ISSN 1436-2449, Vol. 53, no 4, p. 243-248Article in journal (Refereed)
    Abstract [en]

    The 6 wt.% NaOH/4 wt.% urea aqueous solution was proved to be an aqueous nonderivatizing solvent for cellulose by C-13 NMR. O-(2-hydroxyethyl) cellulose (HEC) was prepared by a totally homogeneous hydroxyethylation of cellulose using this new solvent for the first time, and the distribution of substituents within anhydroglucose units (AGU) was examined by C-13 NMR. It was found that the relative reactivity of the hydroxyl groups within AGU and the new hydroxyl group was in the order C-x > C-6 > C-2 > C-3, an analogous functionalization pattern as HEC obtained by the heterogeneous slurry process. The ethylene oxide efficiency in this homogeneous etherification reaction was 20 - 30%.

  • 6.
    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)s2000In: Polymer Bulletin, ISSN 0170-0839, E-ISSN 1436-2449, Vol. 45, no 05-apr, p. 381-388Article in journal (Refereed)
    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%.

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