Evaluation of the hydrocarbon condensation polymerisation reaction by means of model compounds. I. The reaction with n‐alkyl‐bromides

Abstract

AbstractThe title polymerisation involves the reaction in tetrahydrofuran of α‐methylstyrene (M) with lithium in the presence of an alkyl dihalide (RX2) to form copolymers. This paper describes a method of studying the effect of changing the experimental parameters on the structure of these copolymers by replacing the dihalide with the corresponding monohalide (HRX). The study is confined to n‐alkyl bromides and the relative amounts of the molecules HR–RH and HRMnRH (where n = 1, 2, and 3) have been determined by g.l.c. By this means it is shown that the reaction is diffusion controlled and the rate proportional to lithium surface area. At 1 : 1 monomer : monohalide stoichiometry (equivalent to 2 : 1 monomer : dihalide in the polymer system) the product is ∼ 90% HRM2RH indicating that the copolymer under these conditions is highly regular with the repeat unit [M–M–R] predominating. The system is extremely sensitive to the reactant ratio and small deviations from stoichiometry result in significant reductions in dimer yield.