Cationic Copolymerization Of Isobutylene With 4-Vinylbenzenecyclobutulene:Characteristics And Mechanisms

Polyisobutylene(PIB)is widely used for its excellent chemical stability,air tightness,and non-toxicity and harmlessness to the human body.At present,various polyisobutylene-based multifunctional elastomers have been developed.With the continuous advancement of medical technology,the use of polymers as implants in vivo has become a routine operation.Among them,the outstanding biological stability of polyisobutylene groups is receiving increasing attention.The development of polyisobutylene-based biomedical materials has great significance.Significance and application value.Two cationic initiators 2,4,4-trimethylpentane(TMPCl)and 5-tert-butyl-1,3-bis(1-methyl-1-methoxyethyl)benzene(HDCE),using a co-initiator TiC14 and two main initiators respectively to initiate the polymerization of isobutylene(IB),and the addition of proton trapping agent 2,6-di-tert-butylpyridine(DTBP)to ensure the activity of the reaction.The polymerization law and activity characteristics of isobutene during cationic polymerization initiated by the initiation system;the random copolymerization and block copolymerization reaction rules of isobutylene and 4-vinylbenzocyclobutene were investigated,and isobutylene and 4-vinylbenzocyclobutene were proposed.Reaction mechanism during random copolymerization of olefins;characterizes the structural changes after thermal cross-linking of 4-vinylbenzocyclobutene and the thermal and mechanical properties of isobutene and 4-vinylbenzocyclobutene copolymers after thermal crosslinking Performance changes.The results show that:? The conversion rate of isobutene polymerization initiated by TMPCl/DTBP/TiCl4 system can reach 96%at 90 min.The molecular weight of polyisobutylene increases linearly with the monomer conversion rate and the molecular weight distribution is between 1.20 and 1.35;random copolymerization of isobutene and 4-vinylbenzocyclobutene has no activity.The molecular weight of the random copolymer gradually decreases as the feed ratio of 4-VBCB increases,and the molecular weight distribution increases with the feed amount of 4-VBCB.Larger and larger;calculated the monomer reactivity ratios of IB and 4-VBCB random copolymerization,respectively,r1=0.47,r2=2.08;proposed the reaction mechanism of IB and 4-VBCB random copolymerization,namely Compared with IB,VBCB is more prone to get protons from living polymer chains to become a new active species core,which causes chain transfer.The 4-VBCB segment in polymer chains also undergoes self-coupling and causes chain transfer.?HDCE/DTBP/TiCl4 Isobutene polymerization initiated by the system can be 96%at 50min.The molecular weight of polyisobutylene also increases linearly with the conversion of monomers,and the molecular weight distribution is between 1.10?1.20;both initiation systems have achieved cationic controlled polymerization,HDCE/DTBP/TiCl4 has higher efficiency than TMPCl/DTBP/TiC14.The block copolymer p(4-VBCB-b-IB-b-4-VBCB)of IB and 4-VBCB was successfully synthesized using HDCE/DTBP/TiCl4 as the initiation system;Based on the introduction of styrene,the p(styrene-block-4-VBCB)-PIB-P(styrene-block-4-VBCB)terpolymer was successfully synthesized.The copolymerization can be increased by increasing the amount of styrene.The molecular weight of the polymer indirectly regulates the glass transition temperature of the copolymer.?The polymer was heated in a solid form at 250? to achieve the cross-linking of the copolymer.The cross-linked copolymer was characterized by nuclear magnetic resonance,carbon,and infrared spectroscopy.Cross-linked formation was found in all three spectra.8-membered ring structure;Through DSC and TGA characterization analysis,the copolymer will increase its glass transition temperature and thermal decomposition temperature after heat treatment cross-linking;the cross-linking strength of the copolymer will increase with the extension of heat treatment time,After the heat treatment for about 30 minutes,the cross-linking strength no longer changes greatly;the strength of the copolymer is greatly improved after the cross-linking and curing.