Synthesis of Fluoropolymers in Supercritical Carbon Dioxide

Abstract

Fluoropolymers are used in many technologically demanding applications because of their balance of high-performance properties. A significant impediment to the synthesis of variants of commercially available amorphous fluoropolymers is their general insolubility in most solvents except chlorofluorocarbons (CFCs). The environmental concerns about CFCs can be circumvented by preparing these technologically important materials in supercritical fluids. The homogeneous solution polymerization of highly fluorinated acrylic monomers can be achieved in supercritical carbon dioxide by using free radical methods. In addition, detailed decomposition rates and efficiency factors were measured for azobisisobutyronitrile in supercritical carbon dioxide and were compared to those obtained with conventional liquid solvents.

Propagation Rate Coefficients of Styrene and Methyl Methacrylate in Supercritical CO2

“…4 Homogeneous polymerizations in supercritical CO 2 have been performed for fluorinated monomers. 1 The decomposition kinetics and initiator efficiencies in CO 2 differ from that in other media. The rate constant for AIBN decomposition was 2.5 times slower in CO 2 than in benzene.…”

“…Near-critical or supercritical carbon dioxide is rapidly becoming an attractive alternative as a continuous phase in homogeneous 1 and heterogeneous radical polymerizations. 2 A review on chain polymerizations in supercritical fluids appeared recently.…”

“…Initiator efficiencies were very high (>80%) as a consequence of negligible solvent cage effects in supercritical CO 2 , as this medium has a very low viscosity. 1,6 Some early kinetic studies on the γ-radiation-induced precipitation polymerization of ethylene in liquid carbon dioxide 5 showed that there were no large effects on the propagation rate as compared to bulk polymerizations. In heterogeneous polymerization in the presence of CO 2 , the large plasticization effects have a dramatic effect on diffusivities 7,8 and hence termination rate coefficients.…”

Reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in fluid CO2

“…In an attempt to further elucidate the RAFT mechanism it seems rewarding to perform polymerization experiments in fluid carbon dioxide. Fluid CO 2 as a solvent for radical polymerization has been demonstrated to be a promising alternative reaction medium for the synthesis of polymers [18]. It is non-toxic, non-flammable, relatively inexpensive, naturally abundant, and generally regarded as safe.…”

Theoretical insights on electron donor–acceptor interactions involving carbon dioxide

“…[1][2][3][4] In particular, efforts to develop molecules and materials that can be easily solvated in scCO 2 have led to the discovery of weak electron donor-acceptor (EDA) interactions between CO 2 (Lewis acid, LA) and compounds containing fluorine atoms (Lewis base, LB), such as fluorinated polymers. [5] The next milestone for advances in the development of CO 2 -philic molecules was represented by the characterization of EDA interactions between CO 2 and carbonyl groups. [6] Indeed, playing with different substituents and building polymers containing the carbonyl function has allowed tuning the solubility in CO 2 and has opened the door to a wider range of applications of this solvent in green processes.…”