Critically Evaluated Rate Coefficients for Free‐Radical Polymerization, 4

Abstract

AbstractPropagation rate coefficients, kp, which have been previously reported by several groups for free‐radical bulk polymerizations of cyclohexyl methacrylate (CHMA), glycidyl methacrylate (GMA), benzyl methacrylate (BzMA), and isobornyl methacrylate (iBoMA) are critically evaluated. All data were determined by the combination of pulsed‐laser polymerization (PLP) and subsequent polymer analysis by size‐exclusion chromatography (SEC). This so‐called PLP‐SEC technique has been recommended as the method of choice for the determination of kp by the IUPAC Working Party on Modeling of Polymerisation Kinetics and Processes. The present data fulfill consistency criteria and the agreement among the data from different laboratories is remarkable. The values for CHMA, GMA, and BzMA are therefore recommended as constituting benchmark data sets for each monomer. The data for iBoMA are also considered reliable, but since SEC calibration was established only by a single group, the data are not considered as a benchmark data set. All kp data for each monomer are best fitted by the following Arrhenius relations: CHMA: $k_{\rm p} = 10^{6.80} \;{\rm L} \cdot {\rm mol}^{ - 1} \cdot {\rm s}^{ - 1} \exp \left( {{{ - 23.0\;{\rm kJ} \cdot {\rm mol}^{ - 1} } \over {{\rm R} \cdot T}}} \right)$, GMA: $k_{\rm p} = 10^{6.79} \;{\rm L} \cdot {\rm mol}^{ - 1} \cdot {\rm s}^{ - 1} \exp \left( {{{ - 22.9\;{\rm kJ} \cdot {\rm mol}^{ - 1} } \over {{\rm R} \cdot T}}} \right)$, BzMA: $k_{\rm p} = 10^{6.83} \;{\rm L} \cdot {\rm mol}^{ - 1} \cdot {\rm s}^{ - 1} \exp \left( {{{ - 22.9\;{\rm kJ} \cdot {\rm mol}^{ - 1} } \over {{\rm R} \cdot T}}} \right)$, iBoMA: $k_{\rm p} = 10^{6.79} \;{\rm L} \cdot {\rm mol}^{ - 1} \cdot {\rm s}^{ - 1} \exp \left( {{{ - 23.1\;{\rm kJ} \cdot {\rm mol}^{ - 1} } \over {{\rm R} \cdot T}}} \right)$. Rather remarkably, for the methacrylates under investigation, the kp values are all very similar. Thus, all data can be fitted well by a single Arrhenius relation resulting in a pre‐exponential factor of 4.24 × 106 L · mol−1 · s−1 and an activation energy of 21.9 kJ · mol−1. All activation parameters refer to bulk polymerizations at ambient pressure and temperatures below 100 °C. Joint confidence intervals are also provided, enabling values and uncertainties for kp to be estimated at any temperature.95% joint confidence intervals for Arrhenius parameters A and EA for cyclohexyl (CHMA), glycidyl (GMA), benzyl (BzMA), and isobornyl (iBoMA) methacrylate; for details see text.magnified image95% joint confidence intervals for Arrhenius parameters A and EA for cyclohexyl (CHMA), glycidyl (GMA), benzyl (BzMA), and isobornyl (iBoMA) methacrylate; for details see text.