Living Carbocationic Copolymerizations. V. Synthesis of Isobutylene/p-Methylstyrene Copolymers with the Constant Copolymer Composition Technique in the Leidenfrost Reactor

Abstract

Living copolymerization of the isobutylene (IB)-p-methylstyrene (pMeSt) monomer pair in combination with the constant copolymer composition (CCC) technique produces high molecular weight ( M _n ≈ 100,000 g·mol^?1) and narrow molecular weight distribution ( M _w/ M _n ≈ 1.45) compositionally uniform IB/pMeSt copolymer molecules in the industrially important IB/pMeSt = 97–99/3–1 mol% composition range. Syntheses were carried out with TiCl₄ coinitiator in n-butyl chloride homogeneous solution at ?85°C by the use of the Leidenfrost reactor (i.e., by direct cooling of the charge with liquid nitrogen). In order to carry out the CCC technique it was necessary to obtain reliable copolymerization reactivity ratios. These investigations led to r_IB = 0.5 ± 0.1 and r _pMeSt = 10 ± 4. The attainment of CCC and living copolymerization conditions has been quantitatively demonstrated by dedicated diagnostic plots. Specifically, the attainment of CCC conditions was proven by the analysis of composite rate plots (comonomers input and corresponding copolymer formed versus time) and composition plots (comonomer composition in feed and copolymer formed versus weight of copolymer formed, W _p), and living copolymerization was proven by linearly ascending number-average molecular weight of copolymer ( M _n) versus W _p plots starting at the origin.