An alternative method to estimate the bulk backbiting rate coefficient in acrylate radical polymerization

Abstract

An alternative method to estimate the backbiting rate coefficient in acrylate polymerization is presented and successfully applied to experimental data.

Abstract

Based on a pulsed laser polymerization-size exclusion chromatography (PLP-SEC) analysis, an alternative method to estimate the bulk backbiting rate coefficient k _bb in acrylate radical polymerization is presented. For different solvent volume fractions (0–0.75), using the unsaturated analogue of the monomer as a solvent to rule out solvent effects, regression analysis is applied to inflection point data in the low frequency range (< ca. 100 s ⁻¹) only, which can be scanned with less expensive PLP equipment. Variation of the solvent volume fraction allows the independent alteration of the average mid-chain radical lifetime and improvement in the sensitivity of the method to estimate k _bb confidently. The robustness of the method is verified considering in silico generated data including large artificial errors. The method is applied to experimental data of 2,2-dimethoxy-2-phenylacetophenone (DMPA) initiated PLP of n-butyl acrylate, taking butyl propionate as the solvent. A k _bb value of 171 ± 21 s ⁻¹ (303 K) is found, in good agreement with literature data. The method presents a generic approach for the estimation of k _bb for other acrylate monomers, allows a complete statistical analysis, and can be used as a complementary tool for existing methods. In the long term, the method can even be extended for the simultaneous estimation of the bulk k _bb and mid-chain radical propagation rate coefficient k _p,m.