Propagation Rate Coefficients for Vinylidene Fluoride Homopolymerizations

Abstract

For the first time individual propagation rate coefficients, k p, for the homopolymerization of vinylidene fluoride (VDF) have been determined in homogeneous phase reactions with supercritical carbon dioxide. Experiments combining pulsed laser initiation and polymer analysis by size-exclusion chromatography were carried out for temperatures up to 90 °C and pressures up to 1100 bar. Absolute polymer molar masses required for the determination of k p were calculated on the basis of experimentally derived Mark–Houwink constants. A general equation k p(VDF) = f(p,T) was derived by applying multiple regression analysis of k p data. All data may be expressed by ln[k p/(L·mol–1·s–1)] = 19.96 – 3633 K/T + 0.27 p/bar × T –1/K–1. Due to the fluorine atoms in the monomer the kinetic data is significantly different from the nonfluorinated structural analogue ethene. For example, at 60 °C and 1000 bar VDF k p is 19400 L·mol–1·s–1, while k p for ethene is by a factor of 200 lower.

Propagation Kinetics of Isoprene Radical Homopolymerization Derived from Pulsed Laser Initiated Polymerizations

“…This reasoning does not explain why Δ V # of ethene and VDF k p is significantly higher than all other values despite the fact that the least steric hindrance is associated with ethene or VDF propagation. Previously, this finding was explained with the large differences in density of the monomer and polymer for both systems, which are 40% for VDF and 50% for ethene 33. For the liquid monomers typically the difference is lower, e.g., for methyl methacrylate and its polymer the density difference is around 25% 39.…”

“…Multiple regression analysis according to Equation was carried out. Previously, this equation was successfully applied to describe the temperature and pressure dependence of k p in styrene, ethene, and vinylidene fluoride homopolymerizations 31–33 with p given in bar and T in K. Fitting of Equation to the experimentally derived k p data listed in Table S1, Supporting Information was performed using the R Project for Statistical Computing (https://www.r-project.org/).…”

“…Previously, this equation was successfully applied to describe the temperature and pressure dependence of k p in styrene, ethene, and vinylidene fluoride homopolymerizations. [31][32][33] k…”

“…Previously, this finding was explained with the large differences in density of the monomer and polymer for both systems, which are 40% for VDF and 50% for ethene. [33] For the liquid monomers typically the difference is lower, e.g., for methyl methacrylate and its polymer the density difference is around 25%. [39] Following this line, it is reasonable that isoprene k p is associated with an intermediate value of ΔV # .…”

Insight into the Intermolecular Interaction and Free Radical Polymerizability of Methacrylates in Supercritical Carbon Dioxide

“…Pulsed laser polymerization (PLP) is reported to be an effective technique to determine the propagation rate coefficients (kp) of a series of monomers (MMA, MAA, styrene and vinylidene fluoride, etc.) in the free radical polymerization in both scCO 2 and organic solvent systems [36][37][38]. While the report on such determination of the alkyl 2-trifluoromethacrylate(s) monomer (such as MTFMA or TFMAA) has not been seen/available so far.…”