Synthesis of Fluorinated and Hydrocarbon Ester Functionalized Poly(p-phenylenes) and Their Solubility in Supercritical Fluids

Abstract

Monomers of the structure 2,5-dichloro-1,4(RO 2 C) 2 benzene, where R = CH 2 CF 2 CF 3 (la), -(CH 2 ) 2 CH 3 (1b), -CH 2 CH 2 (CF 2 ) 5 CF 3 (1c), and -(CH 2 ) 7 CH 3 (1d), were prepared and characterized in the study. Polymerization by the Ni-catalyzed/Zn-mediated homocoupling methodology afforded poly(p-phenylenes) 2a-2d. The polymers obtained after precipitation into methanol showed molecular weights (M n , relative to polystyrene standards) in the range 7000-13 000. The regiochemistry in the polymer was deduced to be approximately 70% head-to-tail with the remainder head-to-head. The polymers displayed excellent solubility in common polar organic solvents such at THF and chloroform. The poly-(p-phenylenes) 2a and 2b showed no solubility in supercritical ethane, propane, butane, and carbon dioxide even at 190 °C and 35 000 psia. Polymer 2d was remarkably soluble in the supercritical hydrocarbon solvents at low pressures (1000 psia). However, 2d does not dissolve in supercritical carbon dioxide. The fluorinated poly(p-phenylene) 2c dissolved in the supercritical hydrocarbons at pressures below 6000 psia, and it dissolved in carbon dioxide at pressures as low as 1000 psia at 25 °C.