The Study Towards The Synthesis Of Polyisobutylene-based Copolymer By Cationic Polymerization

In this paper we synthesized two kinds of isobutylene-based rubber by cationic polymerization,poly?IB-co-IP?copolymer?butyl rubber?and poly?IB-co-p-MeSt?copolymer,respectively.In the synthesis of butyl rubber,we mainly researched the butyl rubber which is initiated by dual initiator system with wide distribution and discussed the effect of the third component--ethyl acetate to the polymerization of butyl rubber.The products were characterized by the Size Exclusion chromatography?SEC?.The results showed that:?1?Synthesis of butyl rubber by dual initiator system of H₂O/EADC and H₂O/TiCl4,the yield of the polymer was 94.25%,and the number-average molecular weight was 234,000 g/mol.SEC spectrum showed a broad peak shape.And in about20min,there was a smaller hump,which represented the existence of butyl rubber with high molecular weight,and all these demonstrated that by dual initiation system,butyl rubber with a broad molecular weight distribution could be successfully synthesized?2?Ethyl acetate can produce complex reaction with active center,thus making the active center stable.All the active centers could reach and keep a stable state when the concentration of ethyl acetate was in the range of 10ul¹5ul.Under this condition,the polymerization became mild and the relative molecular mass increased.In the system of the polymerization of poly?IB-co-p-MeSt?,we systematically discussed the main factors on the influence of synthesis.The main factors include:monomer concentration,initiator?H₂O?,co-initiator?Al₂Et₃Cl₃?,polymerization time,polymerization temperature and so on.The molecular weight of poly?IB-co-p-MeSt?and its molecular weight distribution was obtained by size-exclusion chromatography?SEC?The microscopic structure of poly?IB-co-p-MeSt?was characterized with¹H-NMR and ¹³C-NMR.The results showed that:The lower the polymerization temperature was,the higher the relative molecular weight can get.So the polymerization temperature should be set at-90?.Considering the significance of industrialization and the effect of mass and heat transfer on the polymerization system,the monomer concentration should be in 17.5wt%.The main initiator H₂O,determined the number of the reactive species in the living polymerization.Co-initiator,Al₂Et₃Cl₃,not only forms active center with H₂O through complexation,but also forms complexes with impurities such as trace water in the system,thereby purifies the polymerization system.The best ratio of Al₂Et₃Cl₃ and H₂O is 9:1.The viscosity of the polymerization system increased as the reaction time increased.When the poymerization temperature was low at the early stage of polymerization,the reaction was stable and the molecular weight was relatively high.After 60s later,as the rate of heat generation increased,the molecular weight distribution become wider and the molecular weight becomes lower,hence the reaction yield got increased.Considering the molecular weight and the reaction yield,the reaction time should be controlled within 120s.Under this condition,the relative molecular weight of poly?IB-co-p-MeSt?copolymer is about 330,000 g/mol and reaction yield is about 95%.In the chain segment,the distribution of?-methylstyrene is homogeneous,and its molar concentration is 3.84%.