聚乙醇酸熔融水解性能及动力学的研究

Study on hydrolytic degradation and kinetics of polyglycolic acid under melting state

用一步反应合成了聚乙醇酸,并系统地研究了聚乙醇酸在蒸馏水中的熔融水解规律。利用红外光谱对聚乙醇酸的结构进行了分析,测定了聚乙醇酸的质量损失率、特性黏数、结晶度和介质的p H值。结果表明,在熔融水解过程中,聚乙醇酸的化学结构没有发生变化、质量损失逐渐增大、特性黏数和介质的p H值逐渐降低。熔融降解过程中,聚乙醇酸的结晶度前期上升,后期下降。质量损失率和介质的pH值与时间均呈线性动力学关系,相关系数分别为0.982 2,0.953 1,速率常数分别为4.395 h-1,0.06 h^(-1);特性黏数随时间的变化规律符合动力学方程ln([η]0/[η])=kt,相关系数为0.939 7,降解速率常数为0.031 8h^(-1)。聚乙醇酸熔融水解降解程度比在磷酸盐缓冲溶液水解大得多。

In present investigation, a study on hydrolytic degradation of polyglycolic acid synthesized by one- step reaction was carried out under melting state. Under mehing state, hydrolytic degradation of polyglycolie acid has been investigated in distilled water systematically. The chemical structure of polyglycolic acid was an- alyzed by FTIR. To better understand degradation process, weight loss, intrinsic viscosity, degree of crystal- linity of the polyglycolic acid and pH value of solution were measured. The chemical structure of polyglyeolic acid did not change during melting hydrolytic degradation. Melting hydrolytic degradation occurred with an in- crease in weight loss, a decrease in intrinsic viscosity and a decrease in pH. Melting hydrolytic degradation al- so occurred with an increase in erystallinity during the initial degradation period and then a decrease after- wards. During melting degradation, the relations of percentage weight loss and pH with time are linear, the correlation coefficients are 0. 982 2 and 0. 953 1 and the rate constants are 4. 395h-1 and 0.06h-1 respective- ly. The time variation of intrinsic viscosity obeys the kinetic equation, ln（ [ η]0/[ η] ） = kt, the correlation coefficient is 0. 939 7, the rate constant is 0.031 8h- 1 Under melting hydrolytic degradation, the degradation degree of polyglycolic acid was much greater than that in the phosphate buffer solution.