Solvent Influence on Propagation Kinetics in Radical Polymerizations Studied by Pulsed Laser Initiated Polymerizations

Critically evaluated rate coefficients in radical polymerization – 7. Secondary-radical propagation rate coefficients for methyl acrylate in the bulk

Benchmark propagation rate coefficient (k_p) data for the radical polymerization of methyl acrylate are provided.

Detailed investigation of the propagation rate of urethane acrylates

Propagation rate coefficients are provided—for the first time—for an entire class of urethane moieties containing acrylates, which display an extremely high propagation rate.

Determination of the propagation rate coefficient of acrylonitrile

For the first time, accurate propagation rate coefficients for acrylonitrile are determined via the pulsed laser polymerization–size exclusion chromatography technique.

Molecular aspects of radical polymerizations-the propagation frequency

The product of the propagation rate constant and monomer concentration is a central issue of radical polymerization. Both quantities are strongly interrelated as the determination of a reliable value of the propagation rate constant requires exact knowledge of the monomer concentration. Even for homogeneous polymerization conditions, exact knowledge of the monomer concentration at the reaction site from the molecular perspective is not trivial. For emulsion polymerizations the situation is additionally complicated by mass transfer events and colloid-chemical effects. Molecular modeling appears as an attractive alternative or complement to the deterministic kinetic description of radical polymerizations.

Surface-Initiated PLP-SEC of Butyl Acrylate and Styrene from Silica Nanoparticles

The pulsed-laser polymerization size-exclusion chromatography (PLP-SEC) technique has been successfully applied to the measurement of the propagation rate coefficient, k(p) , of the surface-initiated polymerizations of butyl acrylate (BA) and styrene, using the silica-immobilized bipedal initiator 4,4'-azobis(4-cyano-N-(3″-triethoxysilylpropyl)-valeric amide) (ACTA). The molecular weight distribution (MWD) of grafted poly(BA) polymerized at 25 °C was structureless, whereas at 5 °C reaction temperature, the MWD exhibited a typical PLP structure with two inflection points. In case of styrene the SEC trace obtained at 26 °C is well structured and shows four inflection points. The propagation rate coefficients k(p) of the surface-initiated polymerizations were about 22% higher in the case of BA and about 27-28% higher in the case of styrene compared to the IUPAC benchmark data.

Transfer to Polymer and Long-Chain Branching in PLP-SEC of Acrylates

Pulsed laser polymerization (PLP) combined with size exclusion chromatography (SEC) is the method of choice for determining propagation rate coefficients. The influence of the long-chain branching in PLP-SEC is investigated using multiple-detection SEC and a recently developed method to detect long-chain branching [P. Castignolles, R. Grab, M. Parkinson, M. Wilhelm, M. Gaborieau, Polymer 2009, 50, 2373.] While little or no long-chain branching is detected in poly(n-butyl acrylate), the error in relevant molecular weights of poly(2-ethylhexyl acrylate) is large (30-100%) due to long-chain branching. Possible variations of propagation rate coefficient with alkyl groups in alkyl acrylates or with the solvent have to be reconsidered.