Chan Woo Lee  Chao Na  Yoshiharu Kimura  Kazunari Masutani 《大分子材料与工程》2016,301(9):1121-1131

A new stereo pentablock copolymer consisting of poly(l ‐lactide) (PLLA: A), poly‐d ‐lactide (PDLA: B), and poly(butylene succinate) (PBS: C) is synthesized by two‐step ring‐opening polymerization of d ‐ and l ‐lactides in the presence of bis‐hydroxyl‐terminated PBS prepolymer that has been prepared by the ordinary polycondensation. The pentablock copolymers (PLLA‐PDLA‐PBS‐PDLA‐PLLA) as well as the triblock copolymers (PLLA‐PBS‐PLLA) obtained as the intermediates show different properties depending on the polymer compositions. In the pentablock copolymers, the direct connection of the PLLA and PDLA blocks allows easy formation of the stereocomplex crystals, while the introduction of the semicrystalline PBS block is effective not only for changing the crystallization kinetics but also for imparting an elastomeric property.

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Jungyub Hyun  Chan Woo Lee  Yoshiharu Kimura 《大分子材料与工程》2015,300(6):650-660

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Nora Hild  Matteo L. Abaecherli  Dirk Mohn  Wendelin J. Stark 《大分子材料与工程》2013,298(11):1143-1148

The present study evaluates the effect of heat treatment on electrospun poly(lactide‐co‐glycolide) fibrous membranes. Both a temperature (75–150 °C) and a treatment time range (5–40 min) are tested. The effect on the fibrous structure is investigated in terms of morphology, showing that with increasing temperature or longer treatment time the fusion of fibres progresses continuously. Additionally, the tensile properties of the various scaffolds deliver results on the effect of increasing fibre‐to‐fibre linkages. Both modulus and yield increase within the heat treatment procedures. The elevated stiffness of the membranes accompanies a loss in porosity. These findings deliver insights into the tailoring of membranes that might be used in the fabrication of customised scaffolds intended for cell culture in tissue engineering.

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Hong Cao  Liao‐bin Chen  Yan‐song Liu  Han Xiu  Hui Wang 《应用聚合物科学杂志》2012,124(5):3678-3684

Osteomyelitis is the inflammation of bone which is treated by a high dose of antibiotics given intravenously for 4–6 weeks. However, at present locally administered antibiotic such as gentamicin poly (methyl methacrylate) (PMMA) bead is nonbiodegradable and a secondary surgery is often inevitable. This study described the biodegradable material poly‐D , L ‐lactide (PLA) with 80 kDa molecular weight that could be used as a potential antibiotic carrier for local drug release. PLA was first dissolved in tetrahydrofuran followed by blending with levofloxacin (LFX) in a physical way. The blend was then molded into beads. The optimized weight ratio between PLA and LFX was designated as 45 : 15. Glass transition temperature and surface ultramicrostructure of the beads were measured. In vitro tests of drug release and bacteriostasis demonstrated that the PLA–LFX beads released high concentrations of antibiotic for the period of time (i.e., 6 weeks), which is needed to treat bone infection. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

    

Ahmed Bakry  Andrea Martinelli  Mariano Bizzarri  Alessandra Cucina  Lucio D'Ilario  Iolanda Francolini  Antonella Piozzi  Sara Proietti 《Polymer International》2012,61(7):1177-1185

The aim of the present work was to study the possibility of building a porous scaffold for tissue engineering with a new bottom‐up approach, obtained by assembling two‐dimensional‐micro, one‐dimensional‐nano sized poly(L ‐lactide) lamellar single crystals. This choice was dictated by the fact that polymer single crystals have structural and morphological features which can be exploited for chemical surface modifications to give a system characterized by a high specific active surface area. Indeed, the outermost amorphous regions can undergo functionalization reactions easily, whereas the inner, relatively inaccessible and inert crystalline core ensures morphological and mechanical stability. The assembling method employed to give the porous structures is based on a mould pressing, salt leaching technique and was found to be facile and versatile. In the first part of this paper we report the experimental results obtained to find the best conditions to achieve a suitable frame in terms of morphology, porosity and mechanical properties. In the second part of the paper, we describe the biological tests performed by using mouse fibroblasts seeded onto scaffolds prepared from pristine and surface hydrolysed lamellae. The results show that the samples obtained are suitable for sustaining cells which can proliferate and reach the inner pores of the scaffold containing hydrolysed single crystals much better than those prepared from pristine lamellae. Copyright © 2012 Society of Chemical Industry  相似文献   

    

Yaru Han  Zhongyong Fan  Zhiqian Lu  Yong Zhang  Suming Li 《大分子材料与工程》2012,297(2):128-135

TMC/LLA copolymers with several TMC/LLA ratios are synthesized and a composite is obtained by reinforcing with short PLGA fibers. In vitro degradation is studied at 37 °C in pH = 7.4 buffer and compared with a PLLA homopolymer. The degradation of the copolymers appears slower than that of PLLA, showing that TMC units are more resistant to hydrolysis than LLA. Compositional changes indicate a preferential degradation of LLA units as compared to TMC ones. Morphological changes with crystallization of degradation by‐products are observed. The composite degrades much faster than the neat copolymer and PLLA because the faster degradation of PLGA fibers speeds up the degradation of the matrix. The composite appears promising for the fabrication of totally bioresorbable stents.

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Masafumi Nakagawa  Fumio Teraoka  Taiji Sohmura 《应用聚合物科学杂志》2011,119(4):2031-2038

It is difficult to control the decomposition rate and the mechanical property of scaffolds after forming the poly(L ‐lactide) (PLLA) scaffolds. The purpose of this study is to control the decomposition rate and mechanical properties of the PLLA plate after forming. We carried out accelerated decomposition experiments using the enzyme on the (PLLA) with various crystallinity, which were prepared by changing the heat treatment condition, and elucidated the relationship between the crystallinity and the decomposition rate. A high positive correlation was observed between the heat treatment temperature and the crystallinity. A high negative correlation was observed between the crystallinity and the decomposition rate. Using the obtained empirical formula, it became possible to calculate the required period to decompose a certain amount of the PLLA if the heat treatment temperature was known. Changing the crystallinity of the PLLA plate could arbitrarily control the decomposition rate of the PLLA plate after forming. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

    

Zhiwei Xie  Gisela Buschle‐Diller  Patricia DeInnocentes  R. Curtis Bird 《应用聚合物科学杂志》2011,122(2):1219-1225

Nanofibrous poly(D,L )‐lactide mats prepared by electrospinning are useful for numerous biomedical applications. However, it was observed that these mats tend to shrink under physiological conditions. In this research, a physical entrapment method to modify the polymer surface with poly(ethylene glycol) was developed to ensure dimensional stability and to increase the hydrophilicity of the surface of the mats. Nanofiber morphology was characterized by scanning electron microscopy. Surface element analysis was performed by high resolution X‐ray photoelectron spectroscopy. Water contact angles were determined to identify surface properties before and after surface entrapment. Canine fibroblasts were prepared and seeded onto the poly(D,L)‐lactide mats, followed by cell morphology study by SEM and cell viability tests by MTT assay, which confirmed the improvement of biocompatibility by surface modification. Taking the results into account, hydrophilic and area‐stable nanofibrous nonwoven mats were successfully produced, with potential applications as in vivo biomedical material. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

    

Raghavendra C. Mundargi  Vidhya Rangaswamy  Tejraj M. Aminabhavi 《应用聚合物科学杂志》2011,122(4):2244-2251

This article explores the application of spray drying technique to produce microparticles of poly(D ,L ‐lactide‐co‐glycolic acid) (PLGA), as well as di‐block copolymer of polylactic acid (PLA) and polyethylene glycol (PEG) (PLA‐PEG), containing zidovudine (AZT), an anti‐HIV drug, to achieve its controlled release over an extended period of time. Of the two polymers studied, PLGA is hydrophobic, whereas PLA‐PEG is hydrophilic and the drug, AZT is water‐soluble. Formulations were developed containing 10 and 25 wt % of AZT giving encapsulation efficiencies (EE) of 66 to 86% for PLGA and 90 to 94% for PLA‐PEG di‐block copolymer. All the formulations were characterized by Fourier transform spectroscopy (FTIR) to investigate the interaction of AZT with polymers and to characterize PLA‐PEG. NMR was also employed to confirm the formation of PLA‐PEG. X‐ray diffraction was used to understand the molecular level dispersion of AZT within the polymeric matrices, while differential scanning calorimetry was employed to assess thermal properties. Scanning electron microscopy was employed to understand the surface morphology of AZT‐loaded microparticles. In vitro release experiments performed in pH 7.4 buffer media extended the release of AZT up to 125 h with PLGA, whereas 30 h were required for releasing AZT through PLA‐PEG microparticles. Cumulative release data were fitted to an empirical equation to understand the nature of release characteristics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2011  相似文献   

    

Yinqing Fan  Zhuyi Yu  Yanhua Cai  Dingding Hu  Shifeng Yan  Xuesi Chen  Jingbo Yin 《Polymer International》2013,62(4):647-657

Adding a nucleating agent is one of the best ways to accelerate the crystallization rate of poly(L ‐lactic acid) (PLLA) so as to obtain a high degree of crystallinity during the process, which will improve the heat distortion temperature of final products. In the work reported, N, N′‐bis(benzoyl)sebacic acid dihydrazide (BSAD) was synthesized and used as a nucleating agent for PLLA. Isothermal and non‐isothermal crystallization behaviors were investigated using differential scanning calorimetry (DSC). The addition of BSAD successfully enhances the crystallization rate of PLLA. A unique phase separation behavior of PLLA/BSAD blends is found from DSC as well as from polarized optical microscopy, which explains the difference of optimal BSAD concentration between isothermal and non‐isothermal crystallization. This is the first recording of a phase separation peak in PLLA/nucleating agent blends using DSC. In thermogravimetric analysis, the enhanced thermal stability indicates that there are strong hydrogen bonds between BSAD and PLLA matrix. BSAD can dissolve in PLLA melt below its melting point through intermolecular hydrogen bonding with PLLA and self‐assemble upon cooling, leading to the surface being capable of nucleating PLLA. Different phase separation temperatures can be used to control the morphology of BSAD, which finally determines the crystallite morphology of PLLA. © 2012 Society of Chemical Industry  相似文献