SYNTHESIS AND CHARACTERIZATION OF HEAD-TO-HEAD POLYISOBUTYLENE AND RELATED POLYMERS

• Main Author: MALANGA, MICHAEL THOMAS
• Language: ENG
• Published: ScholarWorks@UMass Amherst 1982
• Subjects: Polymers
• Online Access: https://scholarworks.umass.edu/dissertations/AAI8229575

Head-to-head (H-H) polyisobutylene was prepared by a Grignard/alkylbromide coupling polymerization using 2,2,3,3-tetramethyl-1,4-dibromobutane as the monomer. The coupling polymerization was carried out at -5 to -10(DEGREES)C in a mixture of benzene and tetrahydrofuran solvent using copper (I) salts as catalysts. The H-H polyisobutylene obtained was found to have bromine end groups and number-average molecular weights of 3,000 to 10,000. The polymer showed interesting crystalline and thermal properties especially in comparison to head-to-tail (H-T) polyisobutylene. H-H polyisobutylene was found to be approximately 50% crystalline under normal conditions, with a melting point of 185-189(DEGREES)C and a glass transition at 85(DEGREES)C. H-H polyisobutylene thermally degrades at 315(DEGREES)C which is some 65(DEGREES)C lower than H-T polyisobutylene under inert atmosphere. Initial studies show that the bond between the two quaternary carbons of the H-H link is the first to break. Blending of the H-H and H-T polyisobutylene was found to yield a two-phase incompatible system as determined by DSC studies. Poly(1,1-dimethylpropane) was prepared from 2,2-dimethyl-1,3-dibromopropane by a sodium Wurtz polymerization. The Grignard/alkylbromide coupling polymerization was determined to be ineffective for this dibromide. The polymer obtained had a glass transition temperature of -17(DEGREES)C and melted between 70 and 90(DEGREES)C. The thermal properties of poly(1,1-dimethylpropane) were compared to those of H-H and H-T polyisobutylene and found to be intermediate between the two. The copolymerization of 3,4-dimethyltetrahydrofuran with selected cyclic ethers was also studied. It was found that although 3,4-dimethyltetrahydrofuran did not homopolymerize under the conditions used in this study, it did readily copolymerize with propylene oxide and epichlorohydrin. The initiator used was PF(,5) and 1:1 copolymers of 3,4-dimethyltetrahydrofuran and either epoxide were obtained. The reactivity ratios for the copolymerization of 3,4-dimethyltetrahydrofuran and epichlorohydrin were found to be r(,1) = 0.22 (+OR-) 0.05 and r(,2) = 0.11 (+OR-) 0.01 respectively. This gave strong indication of an alternating copolymer.