Synthesis And Characterization Of Reactigve Polyisobutylene

Highly reactive polyisobutylene (HRPIB) has been widely used in the field of synthesis of high qualified lube ashless dispersant and fule detergent which produced by heat adduction reaction sanitary technics. The carbocationic polymerization of IB in C4fractions including2-butane, butane, isobutylene,1-butene and1,3-butadiene was conducted at around-30℃. The molecular weight and its distribution of PIB were measured by gel permeation chromatography (GPC) and the chemical structure of end groups in polymer chain were determined by’H-NMR spectroscopy. The effects of the concentrations of the initiating system, reaction conditions, solvent polarity, aging time, temperature and time of polymerization on the molecular weight and molecular weight distribution of the resultant polymers and on the end-group of polymer chain were investigated. The results are shown as follows:The H2O/BF3initiating system possessed high reactivity and high selectivity for the cationic polymerization of IB in the mixed C4fraction in the presence of ED. The highly reactive polyisobutylenes with number average molecular weight from600～2000g/mol and vinylidene content of more than80%could be achieved. The PIBs exhibit unimodal molecular weight distribution and the polydispersity was in the range from1.4to2.5under the proper conditions.The desirable polymerization of IB with relatively slow polymerization rate could be obtained by H2O/TiCl4initiating system in the presence of MeOH under the appropriate reaction conditions and PIB products with low molecular weight (Mn=1600～4600g/mol) and narrow 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 (a-double bonds) in polymer chain ends. The tert-chlorine in PIB chain end obviously decreased with increasing MeOH concentration. The content of a-double bonds increased with decreasing H2O concentration and monomer concentration or prolonging polymerization time. The highly reactive polyisobutylene (HRPIB) with the content of a-double bond more than70%could be synthesized by using H2O/TiCl4initiating system in the presence of MeOH, isopropanol and ether under the appropriate reaction conditions. Furthermore, the preliminary investigation on the IB polymerization in C4fractions shows that the molecular weight, molecular weight distribution and the content of tert-chlorine end group of PIB products decreased while the content of a-double bonds at end group increased with MeOH concentration in the polymerization system. The polymer with Mn of 2000g/mol, Mw/Mn of2.59and vinylidene isomer content of38.9%could be obtained.