Synthesis Of Isobutylene-based Polymers By Grafting From A Star-shaped Multifunctional Polymer

Polyisobutylene and its copolymers are noTab. for their good aging and low permeability air, and cannot be substituted in the sealant and rubber industry because of their special structure. Moreover, star-branched isobutylene-based polymers have been extensively studied for a long time due to their markedly lower solution, bulk viscosities and less shear sensitivity. At the same time, isobutylene can only be polymerized by cationic polymerization, and there are few monomers like that. Therefore, the combination of cationic polymerization and other living polymerization techniques is a very important method to synthesize novel structure and performance polymers.In this studies, the star-shaped multifunctional Poly(St-b-Ip) and Poly(St-b-Bd) copolymers were synthesized in the present of n-BuLi as initiator, THF is used as polar modifier, SiCl₄, SnCl₄ and DVB as coupling agent, cyclohexane as solvent by living anionic polymerization. The GPC results show that the chromatogram reveals a large, well-defined separation between the star and residual arm fraction, and the coupling efficiency is higher. The ¹HNMR results show that the designed St/Ip and St/Bd in the star polymers accord with the experimental values. The amount of non-block of polystyrene is very small, and the block efficiency is higher.A novel branched polymer that each arm of star-shaped Poly(St-b-Ip) and Poly(St-b-Bd) contained several polyisobutylene or butyl rubber chains was first prepared in the present of H2O/AlCl₃ initiating system, CH₃Cl as solvent by combination of cationic polymerization and living anionic polymerization in -90℃. The GPC indicates that the polymer produced has a bimodal molecular weight distribution with a high molecular weight branched mode and a low molecular weight linear component;the FTIR indicates that the peak is due to the out-of-plane C-H bends of the aromatic ring at 696cm¹;the ¹HNMR results show that the polyisobutylene chains have successfully grafted on the star-shaped polymers whatever the adding order, and the grafted efficiency is almost 80%. The amount of the high ends fraction of star-branched polyisobutylene and butyl rubber can be controlled by the amount of the reactive star polymer added;the molecular weight of the amount of the high ends fraction can be controlled by the amount and reacticity of the functionality on the reactive star polymer.The green strength and stress relaxation of star-branched butyl rubber are also studied. The results show that the star-branched butyl rubber with a high molecular weight branchedmode and a low molecular weight linear component has a higher green strength and faster relaxation stress.