Effect of silica nanoparticle loading and surface modification on the kinetics of RAFT polymerization

Abstract

S-(thiobenzoyl)thioglycolic acid was used to synthesize poly(methyl methacrylate) via reversible addition-fragmentation chain transfer (RAFT) polymerization. To study the polymerization kinetics, in situ polymerization reactions were performed with different loading of nanoparticles. To investigate the effect of surface modifi cation on the polymerization kinetics, similar reactions were performed with 3-methacryloxypropyldimethylchlorosilane-modifi ed nanoparticles. Conversion, reaction rate, molecular weight and polydispersity index (PDI) were monitored during polymerization. According to results, pseudo-fi rst order kinetics is achieved, but the rate constant of chain transfer reaction to the RAFT agent (C tr ) has a very small value. Adding nanoparticles causes no considerable change in the kinetic curves, while there is an optimum value for nanoparticles loading in which the polymerization rate reaches its maximum level. A similar trend is observed for molecular weight; however, increasing silica content results in an increase in PDI values. In comparison with pristine silica nanoparticles, the polymerization rate increases slowly in the case of modifi ed particles. Also, molecular weight and PDI for free and graft chains are studied separately. The molecular weight of free chains increases with increasing nanoparticles loading up to 7 wt % and then decreases, while PDI values increase continually by adding nanoparticles. However, for graft chains, molecular weight and PDI values increase with increasing nanoparticle content.

Nanocrystalline cellulose grafted random copolymers of N-isopropylacrylamide and acrylic acid synthesized by RAFT polymerization: effect of different acrylic acid contents on LCST behavior

“…This shows that the content of hydroxyl groups decreases during the graing process. 57 1 H NMR spectra of PNIPAAm, PAA, and their random copolymers by varying AA content are exhibited in Fig. 6.…”

Nanofibers of poly (hydroxyethyl methacrylate)-grafted halloysite nanotubes and polycaprolactone by combination of RAFT polymerization and electrospinning

“…The grafting from method is based on the modification of a substrate by an initiator and subsequent propagation of polymer chains from the substrate. In grafting from reactions, control of grafting density and molecular weight of the surface-attached polymers is commonly achieved by controlled radical polymerization (CRP) techniques [18][19][20][21][22]. In the case of HNTs, attachment of various polymer chains was frequently reported by atom transfer radical polymerization (ATRP) and reversible additionfragmentation chain transfer (RAFT) polymerization.…”

Confinement effect of graphene nanoplatelets on atom transfer radical polymerization of styrene: grafting through hydroxyl groups

“…In CRP methods, nitroxide-mediated polymerization (NMP) [2], atom transfer radical polymerization (ATRP) [3], and reversible addition-fragmentation chain transfer (RAFT) polymerization [4] have been considered largely. Mechanistically, these methods are based on an equilibrium reaction which switches growing chains between active and dormant states.…”