Synthesis of cyclic polystyrene via a combination of intramolecular coupling and ATRP

Cyclic polystyrene with narrow molecular weight distribution was synthesized by intramolecular coupling of α-carboxyl-ω-butylamino heterotelechelic polystyrene using 2-chloro-1-methylpyridinium and triethylamine as the catalyst in highly dilute solution. The linear precursor α-carboxyl-ω-butylamine polystyrene was first prepared by atom transfer radical polymerization using 4-(chloromethyl)benzoic acid as the initiator and followed by nucleophilic substituted with n -butylamine. The results of IR, 1 H NMR, and gel permeation chromatography revealed that highly pure cyclic polystyrene was synthesized via a combination of intramolecular coupling and atom transfer radical polymerization, and can be isolated easily by column chromatography on silica gel using ethyl acetate as the eluant.