Controlled free-radical copolymerization kinetics of styrene and divinylbenzene by bimolecular NMRP using TEMPO and dibenzoyl peroxide

An experimental study on the kinetics of nitroxide-mediated free radical copolymerization (NMRP) of styrene (STY) and divinylbenzene (DVB) is presented. The experiments were carried out in bulk from a mixture of monomers, stable free radical controller (2,2,6,6-Tetramethyl-1-piperidinyloxy, TEMPO), and initiator (dibenzoyl peroxide, BPO), at 120 degrees C, without using a TEMPO-capped prepolymer in the initial mixture. The system studied is a case of bimolecular NMRP, as opposed to the monomolecular NMRP of styrene and other crosslinker previously addressed in the literature by others. The results on total monomer conversion (polymerization rate), molecular weight development, gel fraction, and swelling index are compared against a conventional reference system (a STY/DVB copolymer, also synthesized for this study). No significant auto-acceleration effect was observed in the early and intermediate conversion ranges of the TEMPO-controlled copolymerization of STY/DVB, and the gelation point was significantly delayed.