An experimental study on the kinetics of the reversible addition-fragmentation chain transfer (RAFT) copolymerization of styrene (STY) and divinylbenzene (DVB) is presented. The experiments were carried out in bulk from a mixture of monomers, S-thiobenzoyl thioglycolic acid as RAFT agent, and the initiator dibenzoyl peroxide (BPO) at 80°C. The effect of RAFT agent concentration, including the case without RAFT controller, on polymerization rate, molecular weight development, gel fraction, and swelling index was analyzed. IntroductionCross-linked polymers (polymer networks) are used in many technological areas, e.g., as paints, construction materials, coatings, polymer glasses with high mechanical strength and high thermal stability, superabsorbent materials, food packaging, implants, controlled drug-release matrices, and artificial organs [1,2], to name a few applications. Poly(styrene-co-divinylbenzene) is a cross-linked polymer with attractive properties. It has an excellent stability at high temperatures and under physical stresses and is dimensionally stable under a wide variety of conditions due to its rigid network structure. It finds applications in chromatographic columns, exchange resins [5][6][7][8], and enzyme immobilization [9] and can be used in a wide pH range. It is possible to modify its surface so that it can be used as a catalytic support and for other applications [10].Controlled/living radical polymerization (CLRP) processes allow the synthesis of polymer materials with controlled microstructures which find usage in technologically important areas, such as aerospace, nanotechnology, industrial electronics, and biomaterials [9][10][11][12][13]. Reversible addition-fragmentation transfer (RAFT) polymerization has proven to be one of the most effective CLRP processes because of its advantages over other CLRP techniques (atom-transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization (NMRP)), such as the applicability of the technique to a larger range of monomer types, reaction conditions (temperature and pressure), and processes (homogeneous and heterogeneous) [14,15].Most applications of polymer networks require homogeneous structures to obtain optimal performance. However, polymer networks obtained by free-radical copolymerization of vinyl/divinyl monomers are heterogeneous in nature. It would be desirable to have a synthetic route to synthesize homogeneous polymer networks using free radical technology. This goal may be achieved by copolymerizing vinyl and divinyl monomers in the presence of CLRP controllers [6].The production of polymer networks by controlled/living radical copolymerization (CLRC) techniques, including the copolymerization of vinyl/divinyl monomers, has already been addressed in the literature for the cases of INIFERTER [16][17][18][19], ATRP [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36], NMRP [6,[37][38][39][40][41][42][43][44][45][46][47], and RAFT [48][49][50][51][52][53][54][55][56][57][58][59][60]. A short review of thes...