The Study Of A Novel Initiating System For Synthesizing High-Molecular-Weight Polyisobutylene

The cationic polymerization of isobutylene was carried out by EDC/H2O and BCF/H2O initiating systems in a mixture of methylene dichloride (CH2C12) and n-hexane (n-Hex). The influence of electron donor (ED) concertration, dosage of initiating system, polymerization temperature, polymerization time, isoprene in feed on the cationic polymerization of isobutylene was investigated. On the basis of previous studies, mixed co-initiator comprising of BCF and EDC was researched on polymerization of isobutylene. The effects of the ration of BCF to EDC, aging time, aging temperature, dosage of initiating system, polymerization temperature, solvent polarity, isoprene in feed on monomer weight and molecular weight distribution were investigated. The number-average molecular weight (Mn) and molecular weight distribution (MWD) of high-molecular-weight polyisobutylene and isobutylene-isoprene copolymers (ⅡR) were characterized by GPC method. The microstructure of isobutylene-isoprene copolymers was characterized by1H-NMR. The results show as follows: (1) The PIB with peak molecular weight (Mp) of2.26×105was obtained by conventional cationic polymerization of isobutylene using EDC/H2O as initiating system. By introduction of small amount of ED, polyisobutylen with Mp of5.51×105and relatively narrow MWD of2.09could be obtained using the conventional cationic initiating system EDC/H2O.(2) The cationic polymerization of isobutylene carried out by BCF/H2O initiating system was characterized as one with slow initiation, slow propagation and not easy to chain transfer compared with the polymerization initiated by EDC/H2O. Polyisobutylen with Mp of5.0×105to7.2×105and relatively narrow MWD of1.55to1.77could be obtained using BCF/H2O initiating system and IIR of Mp of4.75×105could also be prepared by such initiating system at-60℃in IP/IB with2%.(3) Using mixed co-initiator comprising of BCF and EDC in conjunction with H2O as initiating system of cationic polymerization could improved moleculer weight of polymer. With the same ration of EDC to IB, the increase of BCF/EDC could increase the Mp of IIR from5.8×104to2.84×105.