Depolymerization kinetics of di(4-tert-butyl cyclohexyl) itaconate and Mark-Houwink-Kuhn-Sakurada parameters of di(4-tert- butyl cyclohexyl) itaconate and di-n-butyl itaconate

Multipulse pulsed laser polymerization coupled with size exclusion chromatography (MP-PLP-SEC) has been employed to study the depropagation kinetics of the sterically demanding 1,1-disubstituted monomer di(4-tert-butylcyclohexyl) itaconate (DBCHI). The effective rate coefficient of propagation, k _p ^eff , was determined for a solution of monomer in anisole at concentrations, c _M ⁰ , 0.72 and 0.88 mol L ^-1 in the temperature range 0 ≤ T ≤ 70°C. The resulting Arrhenius plot (i.e., ln k _p ^eff vs. 1/RT) displayed a subtle curvature in the higher temperature regime and was analyzed in the linear part to yield the activation parameters of the forward reaction. In the temperature region where no depropagation was observed (0 ≤ T ≤ 50°C), the following Arrhenius parameters for k _p were obtained (DBCHI, E _p = 35.5 ± 1.2 kJ mol ^-1 , ln A _p = 14.8 ± 0.5 L mol ^-1 s ^-1 ). In addition, the k _p ^eff data was analyzed in the depropagatation regime for DBCHI, resulting in estimates for the associated entropy (-ΔS = 150 J mol ^-1 K ^-1 ) of polymerization. With decreasing monomer concentration and increasing temperature, it is increasingly more difficult to obtain well structured molecular weight distributions. The Mark-Houwink-Kuhn- Sakurada (MHKS) parameters for di-n-butyl itaconate (DBI) and DBCHI were determined using a triple detection GPC system incorporating online viscometry and multi-angle laser light scattering in THF at 40°C. The MHKS for poly-DBI and poly-DBCHI in the molecular weight range 35-256 kDa and 36.5-250 kDa, respectively, were determined to be K _DBI = 24.9 (10 ³ mL g ^-1 ), α _DBI = 0.58, K _DBCHI = 12.8 (10 ³ mL g ^-1 ), and α _DBCHI = 0.63.