Jian J.,Tsinghua University |
Li Z.-J.,Tsinghua University |
Ye H.-M.,Institute of Polymer Science and Engineering |
Yuan M.-Q.,Institute of Forensic Science |
Chen G.-Q.,Tsinghua University
Bioresource Technology | Year: 2010
Polyhydroxyalkanoate synthase gene phaCah in Aeromonas hydrophila strain 4AK4 was deleted and its function was replaced by phaC1ps cloned from Pseudomonas stutzeri strain 1317 which favors 3-hydroxyhexanoate (3HHx) and longer chain length monomers. Genes fadD and fadL encoding Escherichia coli acyl-CoA synthase and Pseudomonas putida KT2442 fatty acid transport protein, respectively, were introduced into the recombinant with new phaC1ps. Accumulation of a series of novel medium-chain-length polyhydroxyalkanoates (mcl-PHA) consisting of 80-94 mol% 3HHx were observed. The recombinant accumulated 54% poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) in cell dry weight consisting of 94.5 mol% 3HHx or 51% poly(3-hydroxybutyrate-co-3-hydroxyhexanoate-co-3-hydroxyoctanoate) consisting of 82 mol% 3HHx and 16 mol% of 3HO during a two-step cultivation process under nitrogen limitation when grown on sodium hexanoate or sodium octanoate. The two polyesters containing high percentage of 3HHx are physically characterized. They could be used as biodegradable pressure sensitive adhesives, coatings, polymer binding agents in organic-solvent-free paints or a source for chiral R-3-hydroxyhexanoate. © 2010 Elsevier Ltd. All rights reserved.
Lin C.-Y.,Institute of Polymer Science and Engineering |
Hsu S.-h.,National Taiwan UniversityTaipei Taiwan
Journal of Biomedical Materials Research - Part B Applied Biomaterials | Year: 2014
Two different compositions of water-based biodegradable polyurethane (PU) in the form of homogeneous nanoparticles (NPs) were synthesized using biodegradable polyesters as the soft segment. The first PU (PU01) was based on poly(ε-caprolactone) (PCL) diol and the second PU (PU02) was based on 40% PCL diol and 60% polyethylene butylene adipate diol. The PU NP dispersions with different solid contents were sprayed into liquid nitrogen and resuspended in water to generate elastic microspheres (50-60 μm) with different nanoporosities. In vitro degradation analysis revealed that microspheres of PU02 (i.e., PU02 MS) degraded faster than those of PU01 (PU01 MS). Methylene blue was encapsulated during microsphere formation and the release was investigated. Microspheres made from a lower content (10%) of PU02 dispersion (i.e., PU02 MS_10) showed a greater burst release of methylene blue in 6 h, whereas those made from a higher content (30%) of PU01 dispersion (i.e., PU01 MS_30) revealed a prolonged release with a significantly lower burst release. Biocompatibility evaluation using L929 fibroblasts demonstrated that cells were attached and proliferated on microspheres after 24 h. On the other hand, microspheres may further self-assemble into films and scaffolds. Surface modification of microspheres by chitosan may modify the self-assembly behavior of microspheres. Microspheres could be stacked to form scaffolds with different macroporosities. Fibroblasts were successfully seeded and grown in the microsphere-stacked scaffolds. We concluded that the biodegradable and elastic microspheres may be facilely produced from a green and sustainable process with potential applications in drug release and three-dimensional cell culture. © 2014 Wiley Periodicals, Inc.
Yang C.,Institute of Polymer Science and Engineering |
Liu P.,Institute of Polymer Science and Engineering |
Guo J.,Institute of Polymer Science and Engineering |
Wang Y.,Northwest Normal University
Synthetic Metals | Year: 2010
Conductive polypyrrole (PPy) was chemically grafted from the self-assembled monolayer (SAM) coated on expanded vermiculite (VMT), resulting in PPy/VMT nanocomposites after VMT particles were surface modified. X-ray diffraction (XRD) analysis confirmed that the main peaks of PPy/VMT nanocomposites are similar to the SAM-VMT particles, which reveal that the crystal structure of SAM-VMT is well maintained after the coating process under polymerization conditions and exhibit semi-crystalline behavior. Thermogravimetric analysis shows that the thermal stability of PPy/VMT nanocomposites was enhanced and these can be attributed to the retardation effect of amine-functionalized VMT as barriers for the degradation of PPy. The morphology of PPy/VMT nanocomposites showed the sheet structure and encapsulated morphology. The composites possess high electrical conductivity at room temperature, weakly temperature dependence of the conductivity. © 2009 Elsevier B.V. All rights reserved.
Kuo C.-P.,Roosevelt Road |
Chuang C.-N.,Institute of Polymer Science and Engineering |
Chang C.-L.,Roosevelt Road |
Leung M.-K.,Roosevelt Road |
And 3 more authors.
Journal of Materials Chemistry C | Year: 2013
We report the study of the fluorescence switching properties of the conjugated copolymers containing triphenylamine, fluorene, benzo[2,1,3] thiadiazole, and cyclic urea moieties. The copolymers show excellent thermal stability and good solubility in polar organic solvents. While the electrofluorescent device (EFD) of P1 emits yellow light under UV excitation, fluorescence intensity is switched off upon electrochemical oxidation. In addition, the fluorescent behavior of the EFD of P1 can be reversibly switched between the non-fluorescent (oxidized) state and the fluorescent (neutral) state with a superb contrast ratio (If/If0) of 21.4. Furthermore, a white-light electrochemical fluorescence switching device is achieved by blending of P1 (yellow) with P2 (blue). Since the fluorescent conjugated polymers of P1 and P2 have their emission simultaneously quenched under the low working potential, the EFD could show a white-dark state of fluorescence with a high contrast ratio (If/If0) of 14.6. © 2013 The Royal Society of Chemistry.
Liu G.,Institute of Polymer Science and Engineering |
Liu P.,Institute of Polymer Science and Engineering
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2010
The preparation conditions of the monodispersed crosslinked polystyrene nanoparticles decorated with surface carboxyl groups via soapless emulsion polymerization with oleic acid (OA) as emulsifying comonomer (surfmer) and divinyl benzene (DVB) as crosslinker were optimized in the present work. The effects of the amounts of surfmer, crosslinker and initiator added, polymerization time on the particle sizes of the nanoparticles were investigated by the dynamic laser light scattering (DLS) analysis. Monodispersed functional crosslinked polystyrene nanoparticles with the particle size near 250 nm were obtained for the optimum polymerization condition. © 2009 Elsevier B.V. All rights reserved.