Linear polybenzyls. III. Sterically assisted linear polymerization of 2,5-dimethylbenzyl chloride and α-methylbenzyl chloride

The low-temperature Friedel-Crafts step-growth polymerization reactions of 2,5-dimethylbenzyl chloride with TiCl₄—(C₂H₅)₂AlCl catalyst, and of α-methylbenzyl chloride with AlCl₃ catalyst were investigated for the effect of reaction conditions on polymer molecular weight, linearity, glass transition temperature, and crystalline properties. Premature precipitation of highly crystalline poly(2,5-dimethylbenzyl) prevented the preparation of high molecular weight products from this monomer, while most likely an indanyl-type termination reaction limited the molecular weight of poly(α-methylbenzyl). Model reactions indicated that, under proper conditions, the latter could be prepared with 99% para substitution, and these polymers were crystalline.