High performance modification of chemically synthesized biodegradable polyesters

聚(L-乳酸)是以玉米淀粉等可持续资源为原料制成的可生物降解聚合物。但在光泽转变温度(50℃)以上开始软化。因此，将PLLA与三烯丙基异氰尿酸酯(TAIC)混合。将PLLA与TAIC混合后，按不同的辐照剂量进行辐照。测定了凝胶分数和溶胀度，并评价了交联剂的形成。在TAIC浓度为3%时，辐照剂量为50kGy时，PLLA的改性效果最好。该样品的凝胶含量和溶胀度分别为85%和6%。热机械分析表明，未处理的聚乳酸在玻璃化转变温度(Tg)以上出现软化，在90℃附近有明显的伸长率，而在此条件下处理的交联样品在Tg和熔点Tm以上略有软化，但在Tg以上仍保持原始形状。聚乳酸的热稳定性也是在90℃左右进行的，而交联型样品…不仅表现出PLLA的热稳定性，而且还表现出对氯仿等良好溶剂的耐化学性。此外，即使在一次熔融后，交联型PLLA也表现出形状记忆特性。熔融法制备的PLLA结晶度很低，热稳定性较差，因此我们尝试在PLLA样品中加入TAIC，然后进行辐照处理。这种方法显示了部分交联的PLLA的TMA行为，即在Tm处部分软化，但在Tm以上保持其形状。交联剂的引入使交联型PLLA的生物降解性略有下降，但通常在水解后发生生物降解，在实际应用中没有问题。其他化学合成的可生物降解聚合物(如Bionolle)分别与无机粒子或TAIC或TMAIC共混。用这些方法制备了热稳定性和形状记忆可生物降解聚合物。这些化学合成的可生物降解聚合物被细菌生物降解。对分离到的33株细菌进行了生理和形态观察，发现为革兰氏阴性菌和革兰氏阳性菌。较少

Poly(L-lactic acid) is biodegradable polymer made from sustainable resources such as corn starch. But it begins to be softening above the gloss transition temperatue (50℃). Therefore, PLLA was mixed with triallyl isocyanurate (TAIC). After mixed with TAIC, PLLA was irradiated at various irradiation doses. Gel fraction and degree of swelling were measured and evaluated crosslinking formation. At 3% concentration of TAIC, 50 kGy of irradiation dose were the best condition for modification of PLLA. For this sample, gel fraction and degree of swelling were 85% and 6%, respctively. Thermo- mechanical analysis (TMA) of untreated PLLA showed softening above glass transition temperature(Tg) and significant elongation at around 90℃, while crosslinked sample treated under above conditions showed slight softening above Tg and melting point Tm, however it retains original shape even at above Tm. Thermal stability of PLLA was also obtained by annealing at around 90℃, however, the crosslinked sample … More showed not only the heat stability but also chemical proofing with good solvent for PLLA, such as chloroform. Moreover, the crosslinked PLLA showed properties of shape memory, even after once melted. Melt-quenced PLLA has very low crystallinity, which causes poor heat stability, so we tried annealing PLLA sample mixed with TAIC followed by irradiation. This method showed TMA behavior of partially crosslinked PLLA, i.e., partially softening at Tm but retained its shape above Tm. Biodegradability of the crosslinked PLLA was retarded slightly by introduction of crosslinking, however, usually it proceeds biodegradation after hydrolysis, there are no problem after the treatment in practice.Other chemically synthesized biodegradable polymers (e.g., bionolle)were treated with blending with inorganic particles or TAIC or TMAIC. Thermal stable and shape memory biodegradable polymers were obtained by these methods. These chemically synthesized biodegradable polymers were biodegraded with bacteria. 33 strain of bacteria were isolated, which were investigated by physiologicolly and morphologically, ond they are found to be gram negative and gram positive bacteria and fungi. Less