Stable free radical polymerization kinetics of alkyl acrylate monomers using in situ FTIR spectroscopy: Influence of hydroxyl-containing monomers and additives

The homopolymerization and copolymerization of various alkyl acrylate monomers was studied under stable free radical polymerization (SFRP) conditions using in situ FTIR spectroscopy to monitor polymerization kinetics. The IR absorbance corresponding to the C-H deformation of the monomer (968 cm ^-1) was measured to determine monomer conversion in real-time fashion. The monomer disappearance profiles were subsequently converted to pseudo-first order kinetic plots. Altering the alkyl ester chain length and configuration did not reveal a significant trend in the resulting polymerization kinetics. However, addition of 2-hydroxyethyl acrylate (HEA) to a polymerization of n-butyl acrylate (nBA) substantially accelerated the rate of total monomer conversion, increasing the observed rate constant almost two times. ¹H NMR spectroscopy also showed that the resulting HEA/nBAcopolymers were enriched with the HEA monomer. Moreover, a similar but enhanced effect was also observed upon the addition of small amounts of dodecanol to an n-butyl acrylate homopolymerization resulting in more than a doubling of the observed rate constant.