Alkyl chain length effects on copolymerization kinetics of a monoacrylate with hexanediol diacrylate.

Copolymerizations of hexanediol diacrylate with three monoacrylates were analyzed using high-throughput conversion analysis to elucidate the effects of varying alkyl pendant groups at different compositions. Each analyzed copolymerization system contained hexanediol diacrylate (HDDA), and copolymerizations with 30-60 wt % monoacrylate reached nearly complete conversion after 30 s of exposure time. For higher amounts of monoacrylate, the photopolymerization kinetics of the hexyl acrylate (HA) copolymerization were significantly slower than the copolymerization with either ethylhexyl acrylate (EHA) or dodecyl acrylate (DDA). With 20 wt % HDDA, conversion at 30 s with a comonomer of HA was 62+/-3%, as compared to 76+/-3% and 84+/-3% when copolymerized with EHA and DDA, respectively. Model kinetic parameters were estimated for all four monomer systems, with HDDA monomer parameters found to be within the same error when estimated from any of the copolymerizations. With kinetic parameters for each monomer, comparison maps showing the difference in conversion between two copolymerizations were generated. These comparison maps allow for an assessment of two comonomer systems to determine the optimal photopolymerization conditions. Slower photopolymerization kinetics for HA occur at nearly all compositions containing monoacrylate, with the largest reduction occurring between 20 and 40 wt % monoacrylate.