不同软段长度PBT-co-PBS-b-PEG嵌段共聚物的合成与表征

用熔融缩聚法合成了一系列具有不同软段长度的聚对苯二甲酸丁二酯 (PBT) co 聚丁二酸丁二酯(PBS) b 聚乙二醇 (PEG)嵌段共聚物 (PTSG) ,考察了PEG分子量 (Mn(PEG) )及PBS摩尔分数 (MPBS)对材料性能的影响 实验表明 ,随Mn(PEG)增加 ,缩聚反应时间延长 ,所得产物分子量均呈较为对称的单峰分布 ,多分散性指数小于 2 0 硬段序列结构分析显示 ,随MPBS 增加 ,PBT平均序列长度减小 ,而PBS平均序列长度增加 ,二者呈无规分布 .受组成及硬段平均序列长度变化影响 ,材料内部呈微观相分离状态 ,DSC曲线上可分别观察到软、硬段熔点及玻璃化转变温度 ;硬段熔点及结晶度随MPBS升高而降低 ,主要是受其平均序列长度变化及共晶作用所致 .材料断裂延伸率及降解速率均随Mn(PEG)及MPBS增加而增加 ,可见提高软段长度及降低硬段结晶度等均能有效改善共聚物高分子链的柔韧性及亲水性 ,赋予共聚物更好的降解性能 .

SYNTHESIS AND CHARACTERIZATION OF POLY(BUTYLENE TEREPHTHALATE)-co-POLY(BUTYLENE SUCCINATE)-b-POLY(ETHYLENE GLYCOL)BLOCK COPOLYMERS WITH DIFFERENT SOFT SEGMENT LENGTH

The poly(butylene terephthalate)-co-poly (butylene succinate)-b-poly(ethylene glycol) block copolymers (PTSG),employing PEG homopolymers with different number-averaged molecular weight from 400 to 2000 as precursors,with PBS molar fraction (M PBS) varying from 10% to 30% were synthesized by melt polycondensation technique and characterized by means of GPC,NMR,DSC and mechanical testing etc.The result of GPC measurements shows single-modal curves with a polydispersity below 2.0 for the copolymers.Analysis on the sequence distribution of the two hard segments in the copolymer chains reveals that the average sequence length of PBT hard segments decreases while that of PBS increases with the increase of M PBS,and the random distribution of the two hard segments is also validated by the degree of randomness around 1.1.Microphase-separation structure is demonstrated by the appearance of two glass transition temperatures (T g,s,T g,h) and two melting points (T m,s,T m,h) in DSC curves of most samples.Especially,the decrease of the average block length of PBT and the co-crystallization between the two hard segments may cause the depression of the melting point and crystallinity of the hard segments,when M PBS changes from 10% to 30% under constant soft segment length.The increase of elongation at break and equilibrium water up-take with the increase of PEG molecular weight and its weight ratio in the copolymer,as well as the decease of crystallinity of hard segments provide a promising method of modulating the flexibility and hydrophilicity of copolymer chains.