New Telechelic Polymers and Sequential Copolymers by Polyfunctional Initiator-Transfer Agents (Inifers). VI. Chain Transfer, Molecular Weight Distribution, and NMR Study of Telechelic ?,?-Di(tert-chloro)-polyisobutylene

Abstract

This paper concerns an investigation of kinetic aspects of the synthesis and structure of α, ω-di(tert-chloro)-polyisobutylene (C1-PIB-C1). The molecular weight distribution function and dispersion ratio M _w / M _n characteristic for C1-PIB-C1 have been derived. In agreement with theory, M _w / M _n = 1.5 by experiment. An expression for the number-average degree of polymerization, M _n, has been deduced from the distribution function. Chain transfer studies based on this equation and its integrated form are presented. Chain transfer to monomer has been found to be negligible, and chain transfer to inifer was found to be a major process (C_I = 0.3) determining molecular weight and terminal functionality of the polymer. Temperature and solvent polarity (within a modest range) do not affect chain transfer to inifer. NMR spectroscopy of low molecular weight Cl-PIB-C1 confirms the structure of the chain ends to be ∼CH2-C(CH₃)₂Cl. Number-average molecular weights (M _n 's) determined by ¹H NMR spectroscopy and GPC were compared. The accuracy of M _n 's calculated from GPC traces were confirmed by the more accurate and direct NMR method.