端羟基聚乳酸的扩链改性研究

乳酸与2,2-(1,3-亚苯基)-二恶唑啉(1,3-PBO)直接熔融缩聚成端羟基乳酸预聚物(PLBO),以聚乙二醇(PEG)和六亚甲基二异氰酸酯(HDI)聚合制得的端异氰酸酯基聚乙二醇(PEG-NCO)为扩链剂,以二月桂酸二丁基锡为催化剂,对PLBO进行扩链以制备可完全生物降解的聚酯氨酯(PEU)。采用乌氏黏度法、FTIR、DSC、XRD、TG、SEM等方法对各聚合物的结构和性能进行了表征。结果表明:以n(—OH)/n(—NCO)=1的比例投料、反应温度165℃、反应压力0.096 MPa、反应时间20 min为PLBO扩链反应的最佳条件;PEU的最大黏均分子量为44 700;PEG的引入使得PEU的玻璃化转变温度均小于PLA与PLBO,且柔韧性提高;PEU热稳定性提高,分解过程分为两步,第一步为PEU链段中的PLA失重,第二步为PEG-NCO链段的降解;PEU的结晶度降低,进一步说明扩链后聚合物的柔韧性增强。

Study on Chain Extending and Modification of Hydroxylterminated PLA

The hydroxyl-terminated prepolymer(PLBO) was prepared with lactic acid and 2,2-(1,3-phenylene)-bis(2-oxazoline) by direct melt polycondensation.Taking isocyanate-terminated polyethylene glycol(PEG-NCO) prepared with PEG and hexamethylene diisocyanate(HDI) by polymerization as chain extender,dibutyl tin dilaurate as catalyst,to prepare biodegradable poly(ester urethane)(PEU) by chain extension of PLBO.The structure and properties of the polymers were characterized by FTIR,DSC,XRD,TG,SEM,and etc.The results show that the optimum conditions for chain extension of PLBO are n(—OH)/n(—NCO) =1,reaction temperature 165℃,reaction pressure 0.096 MPa,reaction time 20 min;the maximum viscosity-average molecular weight of PEU is 44 700;the introduction of PEG makes the glass transition temperature of PEU smaller than that of PLA and PLBO,which results in the improvement of flexibility;the thermal stability of PEU is improved,its decomposition consists of two steps,the first step is weight loss of PLA segment,the second step is the degradation of PEG-NCO segment;the crystallinity of PEU decreases,which also indicates that the flexibility is enhanced after chain extension.