Global Trends for k_p? Expanding the Frontier of Ester Side Chain Topography in Acrylates and Methacrylates

The Arrhenius parameters of the propagation rate coefficient for two linear methacrylates, two branched methacrylates, and two branched acrylates are determined via the pulsed laser polymerization–size exclusion chromatography (PLP-SEC) method. The Mark–Houwink–Kuhn–Sakurada parameters of these polymers are additionally determined via multidetector SEC of narrowly distributed polymer samples obtained through fractionation, allowing for a correct SEC calibration in the PLP-SEC experiment. The data obtained for stearyl methacrylate (SMA, A = 3.45 (−1.17 to +4.46) × 10⁶ L·mol^–1·s^–1; E_a = 21.49 (−1.59 to +1.90) kJ·mol^–1) and behenyl methacrylate (BeMA, A = 2.51 (−0.80 to +3.06) × 10⁶ L·mol^–1·s^–1; E_a = 20.52 (−1.43 to +1.85) kJ·mol^–1) underpin the trend of increasing k_p with increasing ester side chain length. Propylheptyl methacrylate (PHMA, A = 2.83 (−0.82 to 3.15) × 10⁶ L·mol^–1·s^–1; E_a = 21.72 (−1.20 to +1.64) kJ·mol^–1) and heptadecanyl methacrylate (C17MA, A = 2.04 (−0.66 to +1.71) × 10⁶ L·mol^–1·s^–1; E_a = 20.72 (−1.42 to +1.38) kJ·mol^–1) can be described as a family of branched methacrylates jointly with isodecyl methacrylate and ethylhexyl methacrylate (both published previously), resulting in joint Arrhenius parameters of A = 2.39 (−0.51 to +0.84) × 10⁶ L·mol^–1·s^–1 and E_a = 21.16 (−0.78 to +0.76) kJ·mol^–1. In addition, the corresponding branched acrylates are studied applying high-frequency PLP at a 500 Hz laser repetition rate, resulting in Arrhenius parameters of A = 1.05 (−0.42 to +2.81) × 10⁷ L·mol^–1·s^–1 and E_a = 16.41 (−1.99 to +2.42) kJ·mol^–1 for propylheptyl acrylate (PHA) and A = 8.15 (−2.83 to +10.3) × 10⁶ L·mol^–1·s^–1 and E_a = 14.66 (−1.49 to +1.66) kJ·mol^–1 for heptadecanyl acrylate (C17A).