Anomalous crystallinity in a semi-fluorinated perfluorocyclobutyl (PFCB) polymer containing the hexafluoro-i-propylidene (6F) linkage

The thermal cyclopolymerization of 2,2-bis(4-trifluorovinyloxyphenyl)-1,1,1,3,3,3-hexafluoropropane affords the first example of a semi-crystalline perfluorocyclobutyl (PFCB) polymer and an anomalous feature for a polymer containing the hexafluoroisopropylidene (6F) linkage. Fluoroalkylation of 2,2-bis(hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (6F bisphenol A) with 1,2-dibromotetrafluoroethane, followed by zinc mediated elimination affords the bis(trifluorovinyloxyphenyl) monomer in good yield. High molecular weight polymer (M_w=66,700) with molecular weight distribution approaching 2 was obtained by heating neat monomer at 180 °C for 24 h and 220 °C for 8 h. The stereo-random polymer (ca. 48 to 52 cis- to trans-1,2-disubstituted perfluorocyclobutyl groups) is easily crystallized from the melt despite the presence of the 6F group and a substantial increased fluorocarbon content per repeat unit compared to traditional PFCB polymers. A melting temperature approaching 200 °C was measured by DSC and the crystallinity was characterized by WAXD. Remarkably, the high melting semi-crystalline polymer could be easily dissolved in common solvents in greater than 50 wt% solutions.