异丁烯与对氯甲基苯乙烯正离子共聚合研究

Study of Cationic Copolymerization of Isobutylene and p-(Chloromethyl)styrene

以四氯化钛(TiCl4)、二氯乙基铝(AlEtCl2)、倍半铝(AlEt1.5Cl1.5)、三氯化铝(AlCl3)等路易斯酸为共引发剂,水或枯基醇(CumOH)为引发剂,在-80℃下的正己烷/二氯甲烷(V/V=6/4)的混合溶剂内,研究了异丁烯(IB)与对氯甲基苯乙烯(p-CMS)的正离子共聚合.利用示差凝胶渗透色谱仪(GPCRI)以及核磁氢谱(1H-NMR)对共聚物的表观分子量及分子量分布、共聚组成等进行分析,采用KelenTüd?s与Yezreielv-Brokhina-Roskin法计算了单体竞聚率,初步探讨了p-CMS与IB正离子共聚合的反应机理.结果表明,AlEtCl2、AlEt1.5Cl1.5、AlCl3均可催化大分子间的烷基化反应,产生凝胶;TiCl4作为共引发剂,可以得到无凝胶单峰分布共聚物;邻位氯甲基苯乙烯(o-CMS)不能参与共聚,p-CMS的共聚活性较低,IB与p-CMS的单体竞聚率为rIB=4.67,rp-CMS=0.70;随反应时间延长,共聚物中p-CMS的含量及共聚物分子量均逐渐增加;p-CMS单体自身几乎不参与引发,共聚到大分子链后,苄基氯缓慢参与引发,形成支化.提高共聚合温度至-60和-40℃,聚合速率降低,p-CMS的引发活性未发生明显变化.

Cationic copolymerization of isobutylene(IB) and chloromethylstyrene was investigated with nhexane(Hex)/dichloromethane(CH2Cl2)(V/V = 6/4) as solvent, TiCl4, AlEt1.5Cl1.5, AlEt2Cl, AlCl3 as co-initiators and water or cumyl alcohol as initiators. The molecular weight, molecular weight distribution(MWD) and structure composition of the resulting copolymers were analyzed by gel permeation chromatography(GPC) and 1H-NMR spectroscopy. The reactivity ratios were determined by Kelen-Tüd?s and Yezreielv-Brokhina-Roskin formula, and the copolymerization mechanism was proposed. It was found that co-initiators with strong Lewis acidity, such as AlEtCl2, AlEt1.5Cl1.5 and AlCl3 can catalyze intermolecular alkylations to form gels while no gel formed with the relatively weaker TiCl4. The chloromethylstyrene with para-substituent, i.e., p-(chloromethyl)styrene(p-CMS) was found to have a low reactivity during the copolymerization with IB(rIB= 4.67, rp-CMS=0.70) while the ortho-isomer exhibited no activity. The chemical structure of resulting copolymers indicated that p-(chloromethyl)styrene cannot initiate the polymerization of IB which may be due to its low initiation rate compared to the highly active cumyl group at p-CMS/IB molar ratio of 4.11. However, the benzyl chloride group in the formed copolymer chain can slowly initiate polymerization of IB and p-(chloromethyl)styrene, forming branched structures. The content of p-(chloromethyl)styrene increased with increasing molecular weight and monomer conversion. Systematic research on the branched structure, rheological properties and other physical properties of the resulting copolymers is in progress.