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以磷钨酸/环氧氯丙烷(HPW/ECH)引发四氢呋喃阳离子开环聚合,通过引入链转移剂乙二醇(EG)控制聚四氢呋喃(PTHF)的分子量;以PTHF产率和数均分子量(M n)为试验指标,通过正交设计方法全面考察了聚合温度、聚合时间、ECH、HPW和EG等因素,尤其是链转移剂EG对聚合反应和聚合物分子量的影响.利用热重分析(TGA)分析了HPW从25℃升温至400℃的失水状况;利用红外光谱(FTIR)、核磁共振氢谱(1H-NMR)和凝胶渗透色谱法(GPC)等对聚合物分子结构、分子量及其分布进行了表征.研究结果表明,HPW在170℃下活化2 h活性最高;聚合体系中引发剂与促进剂存在协同作用;通过引入EG作为链转移剂,使EG与THF之间形成络合竞争反应,可有效控制活性链增长,抑制“回咬”反应的发生,减少聚合过程中带环体聚合物的生成;EG的加入有效地控制了PTHF的M n,从12000~23000降低至1100~1700,并使分子量分布(MWD)明显变窄,由双峰分布变为单峰分布;同时,聚合体系的传质效率较高使得聚合物产率从50%提高至80%左右.
Tetrahydrofuran cationic ring-opening polymerization was initiated with phosphotungstic acid / epichlorohydrin (HPW / ECH), and the molecular weight of polytetrahydrofuran (PTHF) was controlled by the introduction of chain transfer agent ethylene glycol (EG); PTHF yield and number average molecular weight M n) as the experimental indexes, the effects of polymerization temperature, polymerization time, ECH, HPW and EG, especially the chain transfer agent EG on the polymerization and the molecular weight of the polymer were investigated by orthogonal design method. TGA analysis of HPW from 25 ℃ to 400 ℃ dehydration conditions; the use of infrared spectroscopy (FTIR), nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC) on the molecular structure of the polymer, the molecular weight And their distribution were characterized.The results show that HPW activated at 170 ℃ for 2 h has the highest activity; polymerization initiator and accelerator synergistic effect; by the introduction of EG as a chain transfer agent, EG and THF form a network The competitive reaction can effectively control the growth of the active chain and restrain the occurrence of the reaction of “back bite” and reduce the formation of polymer with ring body during the polymerization. The addition of EG effectively controls the M n of PTHF from 12000 to 23000 Reduced to 1100-1700, and significantly narrowed the molecular weight distribution (MWD) , From the bimodal distribution into a unimodal distribution; the same time, the high mass transfer efficiency of the polymerization system makes the polymer yield increased from 50% to 80%.