链缠结对等规聚苯乙烯结晶的影响  

Effects of Entanglements on Crystallization of Isotactic Polystyrene

作　　者：于瀛[1] 辛雁[1] 何勇[1] 周之怡[1] 范仲勇[1] 

机构地区：[1]复旦大学材料科学系,上海200433

出　　处：《化学学报》2006年第23期2379-2383,共5页Acta Chimica Sinica

基　　金：国家自然科学基金(No.20474013和20674013)资助项目.

摘　　要：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．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 1.5×10^4 nm^3 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 （σc） was 30.2 erg·cm^-2; the lateral surface energy （a） 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.

关 键 词：等规聚苯乙烯 冷冻升华法 单、寡链聚集体 结晶 

分 类 号：O632.12[理学—高分子化学]