AbstractParaxylylene bisdialkyl sulfonium salts can be polymerized in several different ways, yielding addition polymers as well as condensation polymers. The chemistry leads to a variety of polymers including poly(p‐xylylene), poly(p‐xylylidene), poly(xylylene sulfide)s, poly(xylylene oxide)s, and various α‐substituted polyxylylenes such as poly(p‐xylylene‐α‐dialkylsulfonium chloride). Addition polymers form via xylylene diradical intermediates. Condensation polymerization can be effected either by coupling with aldehydes or by nucleophilic displacem