Anatoly N. Nikitin

Consideration of Macromonomer Reactions in n-Butyl Acrylate Free Radical Polymerization

n-Butyl acrylate (BA) starved-feed solution semibatch experiments with varying final polymer content and monomer feed times were carried out at 138 °C. A full mechanistic model of the system implemented in Predici includes intermolecular chain transfer to polymer and macromonomer propagation as well as backbiting, chain scission, and midchain radical propagation and termination. The importance of macromonomer propagation under these conditions of industrial interest is illustrated by experiment and simulation, with the macromonomer reaction responsible for the significant increase in polymer weight-average molecular weight (

Effect of intramolecular transfer to polymer on stationary free radical polymerization of alkyl acrylates, 4 - consideration of penultimate effect.

\overline M _{\rm w}

Free-radical propagation rate coefficients via n-pulse periodic polymerization

) with time. Rate coefficients for macromonomer propagation (k(mac) ) and β-scission (k(β) ) of k(mac) /k(p)  = 0.55 and k(β)  = 12 s(-1) (with k(p) the rate coefficient for BA chain-end propagation) provide a good representation of experimental

Determination of Intramolecular Chain Transfer and Midchain Radical Propagation Rate Coefficients for Butyl Acrylate by Pulsed Laser Polymerization

\overline M _{\rm w}

The effect of intramolecular transfer to polymer on stationary free radical polymerization of alkyl acrylates

and macromonomer end group data at 138 °C.

Determination of Propagation Rate Coefficient of Acrylates by Pulsed-Laser Polymerization in the Presence of Intramolecular Chain Transfer to Polymer

A penultimate model of acrylate polymerization has been proposed to account for reduced reactivity of radicals formed by monomer addition to midchain radicals. New expressions derived for polymerization rate, number-average degree of polymerization and branching level are used for a comparative analysis of the penultimate and terminal models. The penultimate model has been also implemented into the simulation program PREDICI to conduct a comparative analysis of time dependencies of conversion, cumulative number-degree of polymerization and cumulative branching levels calculated for the different models. The calculations show that, depending on radical reactivity ratio s(i) and monomer concentrations, the predictions from the penultimate model significantly deviate from those of the terminal model.

Effect of Intramolecular Transfer to Polymer on Stationary Free‐Radical Polymerization of Alkyl Acrylates, 5 – Consideration of Solution Polymerization up to High Temperatures

Aspects of applying n-pulse periodic initiation in pulsed laser polymerization/size-exclusion chromatography (PLP/SEC) experiments are studied via simulation of molecular weight distributions (MWDs). In n-pulse periodic PLP/SEC, sequences of n laser pulses at successive time intervals Δt 1 up to Δt n are periodically applied. With the dark time intervals being suitably chosen, n-modal MWDs with n well separated peaks occur. The n-pulse periodic PLP/SEC method has the potential for providing accurate propagation rate coefficients, k p . Among several measures for k p , the differences in molecular weights at the MWD peak positions vield the best estimate of k p under conditions of medium and high pulse laser-induced free-radical concentration. Deducing k p from n dark time intervals (corresponding to n regions of free-radical chain length) within one experiment at otherwise identical PLP/SEC conditions allows addressing in more detail a potential chain-length dependence of k p . Simulations are compared with experimental data for 2-pulse periodic polymerization of methyl methacrylate.