@article{MoellerBeuermann2011, author = {M{\"o}ller, Eleonore and Beuermann, Sabine}, title = {Homogeneous phase copolymerizations of vinylidene fluoride and hexafluoropropene in supercritical carbon dioxide}, series = {Macromolecular reaction engineering}, volume = {5}, journal = {Macromolecular reaction engineering}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1862-832X}, doi = {10.1002/mren.201000031}, pages = {8 -- 21}, year = {2011}, abstract = {Copolymerizations of vinylidene fluoride (VDF) and hexafluoropropene (HFP) were carried out in homogeneous phase with supercritical carbon dioxide up to complete VDF conversion using conventional peroxide initiators. The HFP monomer feed ratios, f(HFP), were varied between 0.65 and 0.20. Depending on f(HFP) amorphous or semi-crystalline copolymers were obtained. f(HFP) also determines the minimum pressure required to allow for homogeneous phase reactions. For example, HFP-rich copolymerizations in 70 wt.-\% CO(2) at 100 degrees C require a pressure of around 500 bar. Further, bulk copolymerizations in homogenous phase were feasible for f(HFP) 0.65 at 900 bar up to complete VDF conversion. Copolymerizations in the presence of perfluorinated hexyl iodide carried out at 75 degrees C gave access to low dispersity polymers. Due to homogeneous phase conditions the use of any surfactants or fluorinated cosolvent is avoided.}, language = {en} } @article{SiegmannMoellerBeuermann2012, author = {Siegmann, Rebekka and M{\"o}ller, Eleonore and Beuermann, Sabine}, title = {Propagation rate coefficients for homogeneous phase VDF-HFP copolymerization in supercritical CO2}, series = {Macromolecular rapid communications}, volume = {33}, journal = {Macromolecular rapid communications}, number = {14}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201200115}, pages = {1208 -- 1213}, year = {2012}, abstract = {For the first time, propagation rate coefficients, kp,COPO, for the copolymerizations of vinylidene fluoride and hexafluoropropene have been determined. The kinetic data was determined via pulsed-laser polymerization in conjunction with polymer analysis via size-exclusion chromatography, the PLP-SEC technique. The experiments were carried out in homogeneous phase with supercritical CO2 as solvent for temperatures ranging from 45 to 90 degrees C. Absolute polymer molecular weights were calculated on the basis of experimentally determined MarkHouwink constants. The Arrhenius parameters of kp,COPO vary significantly compared with ethene, which is explained by the high electronegativity of fluorine and less intra- and intermolecular interactions between the partially fluorinated macroradicals.}, language = {en} }