等规聚苯乙烯的合成及其结晶性能

用负载型钛系催化剂ＭｇＣｌ_２／ＴｉＣＬ_４，ＮｄＣｌ_３／ＡｌＥｔ_３（ＳＮ－１催化剂）在甲苯溶剂中进行苯乙烯的定向聚合，单体转化率。催化效率和产物的等规度随单体浓度增大先是提高，达到最大值后，逐渐下降，等规度最高可达９８％．产物的分子量则随单体浓度增大而增大．ＤＳＣ测定表明，产物中的无规物（ａＰＳ）有利于等规聚苯乙烯（ｉＰＳ）结晶，但对结晶的熔点有降低作用．向产物加入更多的ａＰＳ则由于稀释效应而使ｉＰＳ的结晶度线性下降．在聚乙烯（ＰＥ）／ｉＰＳ共混物中，ＰＥ含量对ｉＰＳ的结晶度无显著影响；但在聚碳酸酯（ＰＣ）／ｉＰＳ共混物中，ＰＣ含量对ｉＰＳ的结晶度影响较复杂．

SYNTHESIS AND CRYSTALLIZATION BAHAVIOR OF ISOTACTIC POLYSTYRENE

tereospecific polymerization of styrene was conducted in toluene using theMgCl_2/TiCl_4, NdCl_3/AlEt_3 catalyst. With increasing monomer concentration , the molecular weight of the products are increase while the polymer yield, the catalytic efficiency , and the isotacticity of the products are all first increased,reaching a maximun , and then decreased gradually. A maximum isotacticity of 98% of the products has been obtained. Results of DSC determinations show that an adequate content of atactic polystyrene (aPS) is favourable of the crystallization of isotactic polystyrene (iPS), but the addition of more aPS linearly decrease the crystallinity of iPS because of the dilution effect. The content of polyethylene (PE) in blends of iPS /PE has no significant influence on the crystallinity of iPS while polycarbonate (PC) excerts a more complicate effect on the crystallinity of iPS in iPS/PC blends.