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化学学报
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化学学报 ›› 2006, Vol. 64 ›› Issue (23): 2379-2383. 上一篇    下一篇

研究论文

链缠结对等规聚苯乙烯结晶的影响

于瀛, 辛雁, 何勇, 周之怡, 范仲勇*   

  1. (复旦大学材料科学系 上海 200433)
  • 投稿日期:2006-03-30 修回日期:2006-04-29 发布日期:2006-12-14
  • 通讯作者: 范仲勇

Effects of Entanglements on Crystallization of Isotactic Polystyrene

YU Ying; XIN Yan; HE Yong; ZHOU Zhi-Yi; FAN Zhong-Yong*   

  1. (Department of Materials Science, Fudan University, Shanghai 200433)
  • Received:2006-03-30 Revised:2006-04-29 Published:2006-12-14
  • Contact: FAN Zhong-Yong

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852

被引次数

5

在1×10－3～2×10－5 g•mL－1溶液浓度范围内, 用溶液雾化冷冻升华法制备了等规聚苯乙烯(i-PS)的单链、寡链非晶态聚集体. 随着溶液浓度降低, i-PS分子链团间的分离程度增大, 链间缠结随之减少, 因此冷冻升华制备的样品中单、寡链线团数目逐渐增多. DSC研究结果表明随着溶液浓度的降低, 冷冻升华样品的结晶温度逐渐降低; 等温结晶得到的晶粒熔点和结晶度降低. 由浓度为2×10－5 g•mL－1溶液制备的i-PS样品在468.3 K熔体结晶60 min后, 得到平均体积约为1.5×104 nm3的单链晶粒. 用SEM观察到晶粒尺寸约为20～50 nm. 采用偏光显微镜(POM)测量了不同温度等温时i-PS单、寡链聚集体球晶的生长速率. 用Hoffmann理论进行了描述, 计算得到了i-PS单链聚集体熔体结晶片晶的端表面能(σe)为30.2 erg•cm－2, 侧表面能(σ)为5.7 erg•cm－2及单分子链折叠功(q)约为4.5×10－13 erg•molecule－1. 与文献值相比, 实验结果表明链缠结对聚合物结晶有很大影响.

关键词: 等规聚苯乙烯, 冷冻升华法, 单, 寡链聚集体, 结晶

Single- and pauci-chain aggregate samples in amorphous state were prepared from aerosols of isotactic polystyrene (i-PS) in a concentration range of 1×10－3～2×10－5 g•mL－1 by the freeze-drying procedure. It was found that as the concentration decreases, the i-PS chain coils would be well separated in solution and the resulting intrachain entanglements may decrease, therefore, the amount of single- and pauci-chain coils, within collected particles obtained via the freeze-drying procedure, increases gradually. The results of freeze-drying samples by DSC indicated that the crystallization temperature shifts lower, the melting point and the crystallinity decrease as the solution concentration decreases. The samples prepared from 2×10－5 g•mL－1 solution are melt-crystallized at 468.3 K for 60 min, then single-chain single-crystal with an average volume of 1.5×104 nm3 was obtained. The crystal grain size was about 20 to 50 nm by the SEM micrograph. By means of the polarized optical microscopy (POM), the spherulite growth rates of i-PS single or pauci-chain congeries are calculated at various crystallization temperatures. With described by the theory of Hoffmann, the critical nucleation parameters of single-chain single-crystal of i-PS were calculated as follows: the fold surface free energy (σe) was 30.2 erg•cm－2; the lateral surface energy (σ) was 5.7 erg• cm－2 and the work of chain folding (q) was about 4.5×10－13 erg•molecule－1. Compared to the values reported in literatures, the results indicate that entanglements have a pronounced effect on the crystallization behavior of polymer.

Key words: isotactic polystyrene, freeze-drying procedure, single- and pauci-chain aggregate, crystallization