丁基锂引发聚合无规立构聚苯乙烯DSC曲线的比较研究

无规立构聚苯乙烯主链上不对称碳原子的构型是无规分布的，通常被认为是典型的非晶聚合物．一些研究者曾在热分析实验中发现从稀溶液中获得的无规立构聚苯乙烯样品ＤＳＣ扫描曲线Ｔｇ附近显现吸热峰，认为这些样品中存在某种局部有序区或准晶结构［１］．如何理解这种非晶...

COMPARISON OF DSC TRACES OF POLYSTYRENES SYNTHESIZED BY ANIONIC POLYMERIZATION

Atactic polystyrenes with molecular weights from 460 to 1550000 were studied by calorimetric measurement.It was found that the samples having molecular weight higher than 10 3 produce initial DSC heating traces with well defined endothermic peaks in the vicinity of T g,the peak size decreased with the increase of molecular weight and then disappeared on rescanning.However,for the samples with molecular weights less than 10 3 no endotherm was observed in the same measurement conditions.The endothermic peaks in DSC traces suggest the existence of localised regions of segmental order in the samples and its possible origin must be the contribution of rr sequence in chains,because these samples have the different steric structures. 13 C NMR determination indicates the proportion of rr triads is lower than 20% for samples of M n<10 3 and larger than 30% for those of M n>10 3.Atactic polystyrenes used in the study were synthesised by solution polymerisation with n butyllithium as initiator,benzene as solvent and alcohol as precipitant.The polymer concentrations were about 1～2% at the end of polymerisation.