Free Radical Propagation Rate Coefficients of N-Containing Methacrylates: Are We Family?

Abstract

Nitrogen-containing methacrylates are a highly interesting class of monomers, yet only very limited data exist describing their propagation rate coefficients, k(p). Herein, we investigate the propagation behavior of three N-containing monomers, namely 2-(N,N-diethylamino)-ethyl methacrylate (DEAEMA), 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA), and 3-(N,N-dimethylamino)propyl methacrylate (DMAPMAE), where we systematically vary the ester side chain with respect to spacer and branching length with the aim of establishing if all so far investigated N-containing methacrylates display family type behavior with regard to k(p). Thus, the Mark-Houwink-Kuhn-Sakurada parameters alongside the Arrhenius parameters of k(p) were determined for these monomers via triple detection SEC and pulsed laser polymerization-size exclusion chromatography (PLP-SEC). The obtained data result in Arrhenius parameters for DEAEMA of A = 2.07 (-0.79 to +3.98) X 10(6) L mol(-1) s(-1) and E-A = 20.45 (-2.02 to +2.28) kJ mol(-1), for DMAEMA of A = 2.64 (-0.79 to +1.98) X 10(6) L mol(-1) s(-1) and E-A = 20.71 (-1.31 to +1.32) kJ mol(-1), and for DMAPMAE of A = 1.22 (-0.54 to +8.02) x 10(6) L mol(-1) s(-1) and E-A = 19.59 (-2.74 to +3.83) kJ mol(-1). The data of the herein investigated monomers are critically compared to the previously published data of 2-(N-ethylanilino)ethyl methacrylate (NEAEMA), 2-(1-piperidyl)ethyl methacrylate (PipEMA), and 2-morpholinoethyl methacrylate (MOMA). It is found that DEAEMA and the previously investigated monomers can be described by one family, leading to a joint Arrhenius description for the four monomers NEAEMA, MOMA, PipEMA, and DEAEMA, best described by A = 1.55 (-0.57 to +3.88) X 10(6) L mol(-1) s(-1) and E-A = 19.68 (-1.76 to +2.60) kJ mol(-1).