Kinetics of RAFT polymerization and copolymerization of vinyl monomers by size exclusion chromatography

Abstract

New method to study kinetics of homo- and copolymerization of vinyl monomers based on size exclusion chromatography (SEC) was developed. The use of this method is associated with some special requirements like identity of an eluent for SEC and the solvent for polymerization, and possessing refractive index increments dn/dc of a monomer and corresponding polymer. Monomer conversion was calculated by comparing intensity of the signals in SEC elution curves attributed to a monomer and corresponding polymer, and taking into account differences in their dn/dc values. The developed method is also applicable to study kinetics of copolymerization including evolution of copolymer composition if one of the monomers is a macromonomer (possess relatively high molecular weight). Suitability of the proposed method was demonstrated by studying kinetics of Reversible Addition Fragmentation Chain Transfer (RAFT) polymerization and copolymerization of 2-hydroxyethyl methacrylate (HEMA) and two poly(ethylene oxide) monomethyl ether methacrylates (PEO5MEMA and PEO9MEMA). It was shown that the new method has some advantages over the other methods used to study kinetics of polymerization (e.g., 1H NMR spectroscopy), since, in the case of SEC with triple detection, it not only enables to calculate monomer conversion and polymerization rate, but simultaneously provides comprehensive information about polymer characteristics (Mn, Mw, Mw/Mn, copolymer composition, etc.) and development of these characteristics during (co)polymerization. It was determined that the synthesized copolymers of HEMA and PEO9MEMA were characterized by low dispersity and gradient distribution of the monomeric units.