可生物降解聚酯P(DHCA-co-LA)的合成与表征

由3,4-二羟基肉桂酸(DHCA)与D,L-乳酸(LA)经熔融缩聚法得到了新型可生物降解聚酯P(DHCA-co-LA),采用傅立叶变换红外(FTIR),核磁共振(1H-NMR)和凝胶渗透色谱(GPC)对该共聚物的组成与相对分子量进行表征,结果表明其结构明确.改变DHCA与LA单体的配比,得到的P(DHCA-co-LA)的分子量和分子量分布在同一数量级.通过差示扫描量热仪(DSC)、紫外(UV)和荧光光谱研究了共聚物的热性能、紫外与荧光性能,结果表明,P(DHCA-co-LA)有明显的玻璃化转变温度(Tg),随LA的投料比从0增加至50 mol%时,其Tg从132.26℃下降至99.12℃;当LA的投料比为20 mol%时,所得到的聚酯型共聚物溶液呈现最强的荧光强度;在紫外光照下,共聚物可进行环加成反应,但交联度总体较低;紫外光照65 min后,在荧光显微镜下观察到交联颗粒形态稳定、有较强的荧光.X-射线衍射(XRD)测定结果显示,由结晶性DHCA和LA共聚形成的P(DHCA-co-LA)为无定形聚合物,有利于生物降解.共聚物在土壤中的降解实验表明,其降解速度随体系中LA含量的增加而减缓.

SYNTHESIS AND CHARACTERIZATION OF A BIODEGRADABLE POLYESTER P(DHCA-co-LA)

A novel polyester P(DHCA-co-LA) based on 3,4-dihydroxycinnamic acid(DHCA) and D,L-Lactic acid(LA) was synthesized by the thermal polycondensation method.The structures and molecular weight of P(DHCA-co-LA) copolymers were characterized by Flourier transform infrared spectroscopy(FTIR),nuclear magnetic resonance(()～1H-NMR) and gel permeation chromatography(GPC).Obvious changes of molecular weight and molecular weight distribution could not be observed when the ratio of DHCA to LA was varied.The thermal and optical properties of the copolymers were investigated by differential scanning calorimetry(DSC),UV spectroscopy and fluorescence spectroscopy.It was found that the P(DHCAco-LA) copolymers showed evident glass transition temperature(T_g).T_g of the copolymers decreased from 132.3℃ to 99.1℃ as the LA content increased from 0 to 50 mol%.The fluorescence spectroscopy indicated that P(DHCAco-LA) copolymers had the strongest fluorescence emission at LA content of 20 mol%.The copolymer solutions exhibited a maximum absorption at 302 nm due to cinnamoyl groups,and the absorption decreased with increasing the UV-irradiation time,indicating that the cinnamoyl group could undergo a photochemical reaction.But the rate of cross-linking reaction is low,which would be responsible for the branched polymer chains.The cross-linked particles with diameter of about 20 μm still have good fluorescence after 65 min UV-irradiation.The X-ray diffraction(XRD) results showed that P(DHCA-co-LA) copolymers were amorphous and these copolymers may have good biodegradable performance.Copolymer rectangular samples,which were buried in soil for 5 months degradation experiments showed that the more LA contents in copolymer,the slower degradation rate of the copolymer,so the speed of copolymer degradation could be controlled.