Application of the Constant Copolymer Composition Technique for the Synthesis of Isobutylene/ p-Methylstyrene Copolymers

Abstract

Compositionally uniform high molecular weight isobutylene (IB)/p-methylstyrene (pMeSt) copolymers have been prepared by using the constant copolymer composition (CCC) technique (see preceding publication) under living carbocationic copolymerization (LC⊕Copzn) conditions. The attainment of the desired copolymer composition of IB/pMeSt = 96.5/3.5 mol%/mol% was demonstrated up to $\overline {{{M}_{n}}} \approx 65,000 g \cdot mo{{l}^{{ - 1}}}$ Мп ≈65,000 g.mol- ¹. CCC and LC⊕Copzn conditions have been quantitated by three diagnostic plots, i.e., two plots that prove the attainment of CCC conditions and one that indicate the existence of LC^⊕Copzn. Specifically, CCC conditions were demonstrated by a rate plot which shows comonomers input together with copolymer formed as a function of time, and a composition plot which shows feed composition together with copolymer composition as a function of copolymer formed (Wp); finally living copolymerization was demonstrated to proceed by plotting ${\overline M _n}$ Мп (number average molecular weight) as a function of W. According to this three prong evidence uniform composition IB/pMeSt copolymers with up to $\overline {{{M}_{n}}} \approx 65,000 g \cdot mo{{l}^{{ - 1}}}$ Мп ≈65,000 g.тo1-1 can be conveniently prepared by living copolymerization under readily achievable CCC conditions at -50 °C. This is the first demonstration of the synthesis of a uniform composition binary copolymer by LC⊕Copzn from a comonomer pair whose reactivity ratios differ by about one order of magnitude.