Synthesis Of Terminal Functionalized Polyisobutylene By Al System Catalytic System

This paper was to prepare high reactive polyisobutylene by the H2O/AlCl3catalyst system with the presence of electron donor(ED) to initiate the cationic polymerization of IB in the C4fraction. The effects of the catalyst system and reaction conditions were studied. The molecular weight and polydispersity of PIBs were determined by Gel Permeation Chromotagraphy, and the microstructure of end group was characterized by1H-NMR analysis, the percentage of exo-olefin was calculated by the integral acreage of1H-NMR spectrum. The results are shown as following:(1)The chemical structure and electron donation of EDs have obvious influences on the polymerization of IB in the C4fraction. The cationic active center can be stable in the presence of stronger ED at the same concentration. At the same time, the conversion is reduced, the molecular weight distribution is narrowed and the percentage of exo-olefin is increased;(2) When [ED]/[Al]<0.2, the conversion can reach80%in the presence of the same ED. The molecular weight of PIB is increased, the molecular weight distribution is narrowed and the percentage of exo-olefin is increased with the increase of ED concentration. When [ED]/[A1]=0.2-0.4, the conversion will be20%below. So the proper concentrate of ED should be [ED]/[A1]=0.05～0.2;(3) The conversion is increased and the molecular weight is reduced with the increasing of the AlCl3concentration. When [Al]/[IB]>7.0×10-3, the percentage of exo-olefin will drop evidently. So the AlCl3concentration should be [Al]/[IB]=2.0×10-3～6.0×10-3;(4) The isomerization reaction can be restrained by lower the polymerization temperature, the percentage of exo-olefin and the molecule weight increase at the same time. The restraint of isomerization reaction by lowering the temperature is different between EDs. When the temperature is low than-25℃, the percentage of exo-olefin can increase above70%in the presence of DMT. However only when the polymerization temperature is low than-40℃, the percentage can increase above70%in the presence of TBP, MKP or TEA;(5) The isomerization reaction will be reactive when the polymerization time is too long. When the time is less than5minutes, the conversion can be increased by prolonging the polymerization time. However, when the polymerization time is more than5minutes, the conversion is no longer increased, but the percentage of exo-olefin will be reduced. Thus the polymerization time should be1～5minutes.By choosing the proper ED and polymerization condition, the high reactive polyisobutylene with above70%of exo-olefin,5000-10000of molecular weight and2.5-3.0of molecular weight distribution was synthesized for the first time, using AlC13as catalyst to initiate the polymerization of IB in the C4compound.