乙二醇对四氢呋喃聚合反应及其产物分子量的影响

EFFECT OF ETHYLENE GLYCOL ON POLYMERIZATION OF TETRAHYDROFURAN AND MOLECULAR WEIGHT OF PRODUCT

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（Mn）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Mn, 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.

Poly-tetrahydrofuran （PTHF） with controllable molecular weight was synthesized in cationic ring-opening polymerization of tetrahydrofuran （THF） using phosphotungstic heteropolyacid （HPW）/epichlorohydrin （ECH） as initiator and ethylene glycol （EG） as chain transfer agent.Effects of various factors （polymerization temperature and time,content of ECH,HPW and EG） on the yield and Mn of PTHF product were comprehensively investigated based on a L16（45） orthogonal experimental design.Influence of chain transfer agent EG on THF polymerization was emphatically studied.Thermogravimetric analysis （TGA） was used to examine the weight loss curve of HPW from 25 ℃ to 400 ℃.Infrared spectra （IR）,proton nuclear magnetic resonance spectroscopy （1H-NMR） and gel permeation chromatography （GPC） were applied to characterize the terminal molecular structure,molecular weight and its distribution （MWD） of PTHF respectively.It was found that the HPW dried at 170 ℃ for 2 h exhibited the highest activity.The initiator and promotor have synergistic effects on THF polymerization.The addition of EG as chain transfer agent in the cationic ring-opening polymerization of THF can effectively control the chain propagation and depress the back-bitting reaction,which is attributed to the complication competition reaction between EG and THF.In the presence of EG,cyclic fraction obviously diminishes in the resulted PTHF product and the Mn of PTHF product decreases from 12000~23000 to 1100~1700.Also PTHF’s MWD is significantly narrowed changing from bimodal distribution into single peak distribution.Moreover PTHF’s yield increases from 50% to 80% because of its higher mass transfer efficiency.