This lecture covers chain copolymerization, focusing on the copolymerization of styrene with acrylonitrile and butadiene. It discusses how copolymer composition and comonomer sequence depend on monomer reactivities, as well as the evaluation of monomer reactivity ratios. The lecture also explores different types of copolymerization behavior, such as ideal, alternating, and block copolymerization. The applicability of the copolymerization equation to various polymerization modes and the influence of solvent effects are highlighted. Additionally, the lecture compares ionic and radical copolymerizations, emphasizing the selectivity and sensitivity of monomer reactivity ratios in these processes.