Reduced Branching in Poly(butyl acrylate) via Solution Radical Polymerization in n-Butanol

A study was conducted to demonstrate that the branching level in poly(n-butyl acrylate (BA) produced through starved-feed semibatch solution free-radical polymerization was reduced 5-fold through introduction of a solvent capable of H-bonding to the acrylate carbonyl group, such as n-butanol (BuOH). Direct evidence of a reduced rate of backbiting in the BA and BuOH system was found through the single pulse pulsed laser polymerization-electron paramagnetic resonance (SP-PLP-EPR) technique. This technique consisted of highly time-resolved online monitoring of radical concentration after production of an intense burst of radicals by pulsed-laser-induced decomposition of a photoinitiator at t = 0. Residual monomer concentrations were determined by gas chromatography and polymer molar mass distribution (MMD) was measured by size exclusion chromatography with a light scattering detector used to verify the MW averages calculated from the refractive index detector and universal calibration.