AbstractThe important factors which control the stereochemistry of polymerization, and thereby the crystalline properties of the polymers so formed, are considered for four different types of reactions including: (1) the cationic polymerization of substituted α‐methylstyrenes to form syndiotactic polymers; (2) the anionic ring‐opening polymerization of substituted β‐propiolactones to form crystalline polyesters; (3) the metathesis ring‐opening polymerization of 1,5‐cyclooctadiene to form poly(1,3‐butadiene)s of controlledcis‐transcontents; and (4) the condensation polymerization of α‐methylbenzyl chloride to form isotactic po