This paper reports preparation of mechanically cross-linked polystyrenes using cyclic macromonomer as a nonbonding cross-linking agent. Emulsion and thermal self-initiated copolymerizations of styrene with a well-defined cyclic macromonomer based on a cyclic polystyrene were carried out to obtain mechanically cross-linked polystyrenes with high swellability. Mechanically cross-linked chloromethylated polystyrene was prepared by thermal self-initiated terpolymerization of the cyclic macromonomer, styrene, and 4-vinylbenzyl chloride.