Coupling Chain Length Dependent and Reaction Diffusion Controlled Termination in the Free Radical Polymerization of Multivinyl (Meth)acrylates

Abstract

The importance of kinetic chain length on termination kinetics has been investigated in cross-linking free radical polymerizations both experimentally and using a kinetic model. The model differs from previous multivinyl polymerization models via incorporation of chain length dependent termination (CLDT) kinetics. Experimentally, kinetic chain length distributions were manipulated, and the impact these changes have on the relationship between polymerization rate, R p, and initiation rate, Ri, was examined over the entire conversion range for both dimethacrylate and diacrylate polymerizations. While the acrylate polymerization exhibits little change, the methacrylate polymerization exhibits significant deviation from the classical dependence of R p on Ri; this dependence continuously changes throughout polymerization. Once the polymerization becomes reaction diffusion controlled, changes in Ri no longer effect the kinetics. The transition from chain length dependent to independent kinetics is predicted when CLDT is incorporated, thus predicting polymerization kinetics more accurately over a range of polymerization conditions.

Photopolymerization of coordinated ionic liquid monomers: Realizing the benefits of structured media using only common reagents

“…1,[9][10][11][12][13] Eventually, increases in the viscosity of the reaction medium also slow monomer diffusion toward the active radical, resulting in a decrease in the rate of propagation and rate of polymerization that is not the result of the decrease in monomer concentration. 1,7,12,[14][15][16] This phenomenon, known as autodeceleration, poses a substantial challenge to chain addition radical polymerization reactions as it can occur at conversions as low as 40% in cross-linked systems and results in significant amounts of residual, unreacted monomer in the product. 1 As the presence of these impurities can detrimentally affect product properties, mass transfer limitations pose a significant challenge for photopolymerization processes.…”

Nonlocal photopolymerization kinetics including multiple termination mechanisms and dark reactions Part I Modeling

“…A p and A t are the parameters that govern the rate at which propagation and termination rates decrease in the diffusion controlled regions. R D is the reaction-diffusion parameter, which is defined as the termination kinetic constant in the reaction-diffusion region divided by the product of the propagation kinetic constant and the instantaneous unreacted monomer concentration M [18,19,30,31,29].…”

“…Note that the expressions for the diffusion controlled kinetics of both k i and k tp ͑cm 3 mol −1 s −1 ͒ will be of the same form as that presented for k p in Eq. (8a) [18,19,29].…”

“…Numerical results describing the behavior of the monomer and polymer concentrations are examined, and n 1 ͑t͒ is then calculated by using Eq. (29). Comparisons of the results of simulations performed retaining 4, 8, and 12 harmonics are made in order to assess the numerical convergence of the method.…”

Semibatch operation and primary cyclization effects in homogeneous free-radical crosslinking copolymerizations

“…The phenomenon becomes much harder to model when divinyl monomers are present, as branching very effectively hinders bulk diffusion of polymer molecules, thus making necessary a thorough revision of the above cited approach as far as termination reaction is concerned. Inadequacy of classical kinetics without including the effect of average chain length on termination before establishment of reaction diffusion regime has been recently proved [40]. Several research groups (Ref.…”