Preparation of nano-HA/PLA composite by modified-PLA for controlling the growth of HA crystals

In order to control the growth of hydroxyapatite (HA) crystals and obtain nano-hydroxyapatite/poly(lactide) (n-HA/PLA) composite with interfacial interaction between the two phases, PLA surfaces were modified with poly(α-methacrylic acid) (PMAA) via photooxidization and UV induced polymerization. FTIR analysis showed that the PMAA was grafted onto the PLA surface and the grafting rate increased with the grafting time. The n-HA/PLA composites were synthesized by modified-PLA and characterized by FTIR, XRD and SEM. Several analyses suggested that the m-PLA could act as a template to manipulate the nucleation and growth of n-HA crystals, control the morphology and size of n-HA crystals as well as their distribution over the organic phase.     

丙交酯的合成与纯化研究

讨论了丙交酯制备过程中的影响因素，用重结晶法得到了高纯度的丙交酯，并通过熔点、红外光谱和氢核磁共振谱对丙交酯进行了表征。     

Morphology and Properties of Poly(L‐Lactide) (PLLA) Filled with Hollow Glass Beads

The morphology, crystalline behavior, and mechanical and thermal properties of poly(L ‐lactide)/hollow glass beads (PLLA/HGBs) composites were investigated. The incorporation of HGBs enhanced the crystallization rate and crystallinity of PLLA, but slightly decreased its elongation at break. In addition, HGBs acted as stress concentration points inducing the plastic deformation of PLLA, leading to increased Izod impact strength. Differential scanning calorimetry results show that annealed PLLA eliminated cold crystallization phenomenon in the region of 100–140 °C and presented a double melting peak around 150 °C. Moreover, annealing was demonstrated to be effective for the improvement of tensile modulus, strength, Izod impact strength and heat distortion temperature of the composites due to the increased crystallinity and more perfect crystals. Silane coupling agents can enhance the interfacial adhesion of the composites, and lead to better mechanical properties. Compared to neat PLLA, the HGBs filled PLLA composites did not exhibit an obvious increase of the density.

     

聚乳酸的合成及其应用

综述了聚乳酸的合成方法，介绍了其生产应用现状。     

Blends of crystalline and amorphous poly(lactide). III. Hydrolysis of solution-cast blend films

Hydrolysis of blend films prepared from amorphous poly(DL-lactide) (a-PLA) and isotactic crystalline poly(D- or L-lactide) (c-PLA) having different c-PLA contents [X = c-PLA/(a-PLA + c-PLA)] was performed in phosphate buffered solution of pH 7.4 at 37°C. The blend films before and after hydrolysis were studied using gel permeation chromatography, tensile testing, differential scanning calorimetry (DSC), and optical rotation. The mass of the blend films remaining after hydrolysis of longer than 20 months was larger with the increasing initial X. The tensile strength of the blend films remained unchanged in the early stage of hydrolysis, followed by a rapid decrease with time, the duration of period for the tensile strength remaining unchanged was longer for the blend films of smaller X. The change in crystallinity, molecular weight, and specific optical rotation during hydrolysis of the blend films revealed that degradation took place preferentially in the amorphous region than in the crystalline region of the blend films. A double melting peak was observed in the DSC spectra of blend films with X = 0.75 and 0.5 after hydrolysis for 20 months. The time difference in the induction of reduction between the tensile strength and the mass due to hydrolysis of the blend films increased with an increase in X. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 855–863, 1997     

Poly(L‐lactide): v. effects of storage in swelling solvents on physical properties and structure of poly(L‐lactide)

The effects of storage at 25°C in swelling solvents having different solubility parameter (δ_s) values of 16.8–26.0 J^0.5 cm^−1.5 on the physical properties and structure of as‐cast poly(L ‐lactide) (PLLA) films was investigated by the degree of swelling (DS), differential scanning calorimetry (DSC), and tensile tests. It was found that PLLA film shows durabity to swelling solvents having δ_s values much lower or higher than the value range of 19–20.5 J^0.5 cm^−1.5 and that the polymer solubility parameter (δ_p) for PLLA is in the value range of 19–20.5 J^0.5 cm^−1.5. The decrease in the glass transition temperature (T_g) and tensile properties and the increase in melting temperature (T_m) and crystallinity (x_c) were larger for PLLA films swollen in solvents having a high DS at 7 days (DS_7days). The slight increase in T_m and x_c for PLLA films after swelling in solvents with high DS_7days values was due to the crystallization of PLLA that occurred during swelling, while the small increase in T_g and elongation at break (ε_B) for PLLA films after immersion in the solvents having low DS_7days values was ascribed to stabilized chain packing in the amorphous region. The T_g, ε_B, and Young's modulus of the PLLA films after swelling in the solvents varied in the ranges of 47–57°C, 4–8%, and 55–77 kg/mm², depending on their DS_7days or δ_s values. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1582–1589, 2001     

聚乳酸在生物医学领域中的应用

简要介绍高分子量聚乳酸的合成方法、良好的生物相容性、可吸收性及生物降解性。通过概述聚乳酸在药物释放材料、眼科材料、外科手术缝合线、骨折内固定材料以及组织工程修复等方面的应用,对其在生物医学领域的研究前景作了进一步展望。     

In vitro Degradation of Poly[(L‐lactide)‐co‐(trimethylene carbonate)] Copolymers and a Composite with Poly[(L‐lactide)‐co‐glycolide] Fibers as Cardiovascular Stent Material

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.

     

聚乳酸纤维的制备及其染色性能分析

比较系统地介绍了聚乳酸纤维(PLA)的合成方法及其特性,并对PLA的染色性能进行了初步的探讨.