Aspects of the Synthesis of Poly(styrene-b-isobutylene-b-styrene) Block-Copolymers Using Living Carbocationic Polymerization
Polymers and High Performance Materials
The effect of the time of styrene addition on the composition of poly(styrene-isobutylene-styrene) (PS-PIB-PS) block copolymers synthesized using a dicumyl chloride/TiCl4/pyridine initiating system and the sequential addition of monomers was investigated at -800-degrees-C. It was found that the addition of styrene at an isobutylene (IB) reaction time significantly exceeding the time necessary for complete IB consumption results in contamination of the material with a substantial amount of homo-PS. Conversely, the addition of styrene to PIB chains formed under conditions of intermediate IB conversion resulted in a very slow buildup in molecular weight after the addition of styrene. This retardation of the rate after the addition of styrene was proven to be the result of a random copolymerization between styrene and unreacted IB. It was also found that the addition of the proton trap 2,6-di-tert-butylpyridine resulted in a narrowing of product polymer molecular weight distribution.
Storey, R. F.,
Chisholm, B. J.
(1993). Aspects of the Synthesis of Poly(styrene-b-isobutylene-b-styrene) Block-Copolymers Using Living Carbocationic Polymerization. Macromolecules, 26(25), 6727-6733.
Available at: http://aquila.usm.edu/fac_pubs/6700