Crystallization behavior of single or pauci chain aggregates of isotactic polystyrene

• 来源期刊: 中国高等学校学术文摘·化学
• 关键词: isotactic polystyrene single chain aggregates pauci chain aggregates crystallization
• 年，卷（期）: 2006,（4）
• 页码范围: 465-468
• 页数: 4页
• 语种: 英文

摘要

Single and pauci chain aggregates of isotactic polystyrene (i-PS) were prepared by the freeze-drying process from dilute solutions with the concentration from 1×10-3 to 2×10-5 g/mL.It was found by DSC measurements that the melting point of samples gradually shifted to lower temperatures with the decrease of the solution concentration used for sample preparation.As a result,the lamella thickness of bulk samples and the samples prepared by the freeze-drying process from a solution of 2×10-5 g/mL was 19.3 and 12.6 nm,respectively,At 468.3 K the half crystallization time (t1/2) of samples freeze-dried from a solution of 1×10-4 g/mL was about 36 s,which was merely one tenth of that of the bulk sample.In addition,the growth rate of spherulite (dr/dt) of samples prepared from a solution of 2×10-5 g/mL was faster than that of the bulk sample annealed at 478.3 K.All these results should be attributed to the fewer entanglements in samples prepared by freeze-drying process from dilute solutions,and presented clear evidence for the influence of chain entanglements on the crystallization behavior of polymers.