TiCl_4共引发异丁烯正离子聚合合成反应活性聚异丁烯

SYNTHESIS OF REACTIVE POLYISOBUTYLENE BY TiCl_4-COINITIATED CATIONIC POLYMERIZATION OF ISOBUTYLENE

由H2O／TiCl4／甲醇或乙醚体系引发异丁烯在二氯甲烷与己烷混合溶剂中进行正离子聚合，探讨甲醇用量、聚合时间等因素对正离子聚合以及产物分子量、分子量分布和末端基结构的影响，并在此基础上探讨TiCl4共引发混合C4馏分中异丁烯选择性正离子聚合以制备活性聚异丁烯的可行性。结果表明，含氧试剂对聚合反应起到明显的调节作用，可适当稳定碳正离子活性中心，降低链增长速率，降低聚合产物的分子量（Mn=1600～4600），使分子量分布明显变窄（Mw／Mn=1.35～2.05），并可调节大分子链末端基结构及其含量。降低聚合体系中微量单体浓度以及适当延长聚合反应时间，均有利于提高聚异丁烯大分子链末端α-双键结构含量。通过TiCl4共引发异丁烯正离子聚合制备出末端α-双键含量可以达到70％以上的低分子量高反应活性聚异丁烯。此外，该引发体系还可引发混合C4馏分原料中异丁烯进行高选择性正离子聚合，得到Mn=2000、Mw/Mn=2．59、端基α-双键含量为38.9％的聚异丁烯。

The carbocationic polymerization of isobutylene （IB） in a mixture of methylene dichloride （CH2 C12 ） andhexane （Hex） was conducted by using H2O as initiator, TICl4 as co-initiator in the presence oxygen-containing additive, such as methanol （MeOH）, isopropanol or ethyl ether. The concentration, TICl4 concentration, monomer concentration, solvent polarity and polymerization carbocationic polymerization, polyisobutylene （PIB） yield, molecular weight （MW） and molecular a small amount of effects of MeOH time on the IB weight distribution（MWD, Mw/Mn ） and end-groups of PIB chains were investigated. The polymerization products were characterized by gel permeation chromatography （ GPC ） and ^1H-NMR spectroscopy. The carbocationic polymerization of IB in Ca fractions including 2-butane, butane, isobutylene, 1-butene and 1,3-butadiene by using H2O/TiCl4/MeOH as initiating system was also investigated. MeOH did play important and effective roles in polymerization initiated by H2O/TiCl4 system. The relative amount of polymers formed via uncontrolled initiation by conventional active speciesdecreased with increasing the concentration of MeOH. MeOH and/or its complexe with TICl4 interacted with the growing chain end to reduce its cationicity and thus to decrease the propagation rate, decrease MW, suppress the uncontrolled chain transfer and termination reactions, and thus to narrow MWD. The desirable polymerization of IB with relatively slow polymerization rate could be obtained by H2O/TiCl4 initiating system in the presence of MeOH under the appropriate reaction conditions, and PIB products with low molecular weight （Mn = 1600 ～ 4600） andnarrow unimodal molecular weight distribution （Mw/Mn = 1.35 ～ 2.05） could be obtained. It is found that MeOH also played an extra important role in increasing the content of vinylidene （α-double bonds） in polymer chain ends. The tert-chlorine in PIB chain end obviously decreased with increasing MeOH concentration. The content of α-double bonds increased with decreasing H2O concentration and monomer concentration or prolonging polymerization time. The highly reactive polyisobutylene （HRPIB） with the content of α-double bonds more than 70% could be synthesized by using H2O/TiCl4 initiating system in the presence of MeOH, isopropanol and ether under theappropriate reaction conditions. Furthermore, the preliminary investigation on the IB polymerization in C4 fractions shows that the molecular weight, molecular weight distribution and the content of tea-chlorine end groups of PIB products decreased while the content of a-double bonds at end groups increased with MeOH concentration in the polymerization system. The polymer with Mn of 2000, Mw/Mn of 2.59 and vinylidene isomer content of 38.9% could be obtained.