以1,2,4-偏苯三羧酸酐(BTAA)和乙醇胺(EMA)为原料,分别采用"二步法"和"一步法"熔融缩聚制备了端羧基超支化聚酯酰胺(HBPEA).第1步利用官能团非等活性原理,在乙醇溶剂中由BTAA中高活性的酸酐基团与EMA中高活性的氨基反应原位生成含1个羟基和2个羧基的AB_2中间体,蒸除乙醇后,再第2步熔融缩聚得到超支化聚酯酰胺,可避免聚合过程中发生凝胶.为便于工业化应用,还采用BTAA与EMA经"一步"熔融缩聚制备了端羧基超支化聚酯酰胺.分别采用核磁共振(NMR)、乌氏黏度计、示差扫描量热仪(DSC)、热失重分析仪(TGA)以及阿贝折射仪等对2种方法所制备的目标产物化学结构和特性黏度等各项性能进行了表征,结果表明:所得聚酯酰胺具有超支化结构,特性黏数为0.12~0.15 d L/g,支化度为0.64~0.65,在350oC之前未发生热失重,玻璃化转变温度为125~126oC,折射率为1.57~1.58,与聚碳酸酯(PC)相近.因此将其作为加工助剂用于PC塑料体系的加工.超支化聚酯酰胺的加入,不仅能改善PC的加工流动性,同时还能改善制品的机械性能和表面光洁度,且不会引起PC色泽的变化.
In this work,all-atom molecular dynamics simulations were employed to study the influence of the side alkyl chain on glass transition behavior of several carbazole trimers(CT) in a temperature range from 423 to 183 K.The glass transition temperatures were obtained from the break in the slope of the volume-temperature curves and found to agree with the experimental values.The short time dynamics of four CT molecules were probed by usingvelocity autocorrelation functions and mean-square displacements.The current studies showed that the dynamics of CT systems can be easily interpreted through the cage effect.Furthermore,the investigation of the torsional autocorrelation function and P_(2-state)/P_(3-state) functions showed that the rotational barriers of side chains can slow down the conformational relaxation and lead to stronger temperature dependence of conformational relaxation.The relaxation time,characteristic time of P_(2-state)(t) and P_(3-state)(t) functions were all found to have Arrhenius-type temperature dependence.
Chunyang YuLi MaWei HuangYongfeng ZhouJingui QinDeyue Yan
