The Cationic Polymerization Of Isobutylene And Styrene With DCC/ALCl₃Initiating System

The cationic polymerization of isobutylene (IB) and styrene (St) by utilizing difunctional initiator dicumyl chloride (DCC) in conjunction with coinitiator AICl3was carried out in CH2Cl2/Hex (40/60, v/v) solvent mixtures. The effects of concentrations of DCC, ED, DtBP and AICl3, aging temperature, polymerization temperature on monomer conversion, molecular weight and molecular weight distribution (MWD) of the product polyisobutylene (PIB) and polystyrene (PSt) were studied in detail. The results show that:(1) The small amount of water in the polymerization system in conjunction with AICl3could induce a conventional uncontrolled rapid polymerization of IB/St and led to polyisobutylene/polystyrene with broad molecular weight distribution. It is found that the GPC trace of resultant polymer obtained by DCC/H2O/AlCl3system exhibit a bimodal distribution, which is attributed to the competition of initiation from two different active centers, i.e., H+AlC13OH-(A) and AlCl4-+C(CH3)2C6H4(CH3)2C+-AlCl4(B). The initiation from active center (B) partly increased in the polymerization system with an increase in DCC concentration and a decrease in AlC13concentration.(2)Uncontrolled initiation from H+AlC13OH-(A) can be decreased by adding a small amount of DtBP in the monomer system. The coaction of DtBP in monomer system and TPA in initiating system could induce a desirable cationic polymerization of IB. The symmetric telechelic PIB with relatively high molecular weight and relatively narrow unimodal molecular weight distribution could be obtained.(3)The alkyl reaction of PSt attribute to polystyrene with a higher molecular weight at peak of1×106mol/g. Lower aging temperature and polymerization temperature could effectively enhance the polarity of solvent inducing a more active initiating center and adding to the possibility of alkyl reaction.(4) The uncontrolled initiation of proton from active center (A) and the chain transfer reaction to monomer could be decreased by addition of electron donor TPA and/or DMP.(5) The polymer obtained with DCC/AlCl3system was partly insoluble in common solvents with its melting temperature scope arrange from100℃to170℃. They were extracted by2-butanone and then separated into an insoluble fraction and a soluble fraction. The insoluble content of PSt ranges from1.36%to56.3%with its melting temperature from140℃to270℃.