Solubility of CF₂-Modified Polybutadiene and Polyisoprene in Supercritical Carbon Dioxide

Abstract

The cloud-point behavior of fluorinated polyisoprenes (FPI) and fluorinated polybutadienes (FPBD) in supercritical fluid (SCF) CO2 are reported at temperatures from 60 to 170 °C and pressures from 1000 to 3000 bar. These fluorinated polymers were prepared by the addition of difluorocarbene (CF2) to the parent polydienes yielding a gem-difluorocyclopropane repeating unit, a segment containing both fluorine and a significant dipole moment. Neither the unmodified polyisoprene starting material nor the hydrogenated variant dissolves in CO2 up to temperatures of 155 °C and pressures of 2600 bar. Both FPI and FPBD dissolve in CO2, but pressures in excess of 1000 bar are needed to obtain a single phase. The PFI and PFBD cloud-point curves exhibit temperature minima at approximately 60 and 80 °C, respectively, likely due to an increase in CO2-CO2 and polymer-polymer interactions relative to polymer-CO2 interactions. As the amount of CF2 incorporation in FPI samples decreases, the cloudpoint curves shift to higher pressures and to higher temperatures. In a series of FPBD samples, an increase in cloud-point pressure with increase in molecular weight is initially large for molecular weights less than 10 5 and then becomes much less at higher molecular weights, as also observed for other polymer-SCF solvent mixtures. This methodology for incorporation of fluorine into macromolecules leads to significant enhancement of solubility in CO2.

Impact of hexafluoroisopropylidene on the solubility of aromatic‐based polymers in supercritical fluids

“…In addition, the CF 3 groups are expected to create local dipole moments in this part of the repeat group. It should also be noted 9 showed that incorporating difluorocarbene (CF 2 ) into a polybutadiene or polyisoprene repeat group yields a gemdifluorocyclopropane repeat group that contains fluorine and has a significant dipole moment. Both the fluorinated isoprene and the butadiene polymers dissolve in CO 2 , but pressures in excess of 1000 bar are needed to obtain a single phase.…”

Enhanced Mechanical Properties in Organofluorosilica Thin Films

“…We propose that the increased stiffness-the resistance of the resulting elastic structure to deflection by an applied force-is due to the presence of fluorine in the CF 3 −(CH 2 ) 2 −[Si−O−] n chains, which is well known to promote orientation by lateral interactions [9]. Too high a level of fluorination, such as in the case of the perfluorinated samples, produces an adverse effect, due to the dominance of interactions within the polymer chains [10]. On the other hand, the influence of the degree of the sol-gel reactions at the moment of spinning is clear comparing films prepared at low spin velocity from sols with the same precursor but with different hydrolysis conditions (TFP3 and TFA3).…”

In situ NMR Methods in Catalysis

“…As exemplified several times in the previous sections, many compoundswhether they be substrates or catalysts-show increased affinity to CO 2 if they are modified by fluorination [167][168][169]. Therefore, the addition of fluorinated pony tails to existing chemical structures or ligand frameworks as exemplified in Sect.…”