Electrophilic Routes to 6F Polymers and Attempted Synthesis of Semi-fluorinated Group IVB Metallocene Polymers

Since the seminal work presented by Olah in 1966 on fluorinated carbocations, several strategies have been presented to introduce fluorinated moieties in polymer backbones via carbocation chemistry. The hexafluoroisopropylidene (6F) group is well known for its ability to enhance thermal properties and processability of polymers. However, its direct electrophilic incorporation into polymers has been largely ignored due to the challenges posed by activating hexafluoroacetone monomer for electrophilic aromatic substitution (EAS). In this article, we review the role of fluorinated carbocations from 1966 up to our recent versatile fluoroalkylation strategy to directly enchain the 6F group in polymers. Via EAS interfacial polymerization we reacted hexafluoroacetone trihydrate (HFAH) with aromatic monomers in triflic anhydride (Tf2O) and 1,2-dichloroethane (DCE) with Aliquat (R) 336. In addition, the polymerization of dibenzo-1,4-dioxin with HFAH is presented. A semi-fluorinated diol, 4,4 '-bis(2-hydroxyhexafluoroisopropyl)diphenyl ether, was synthesized by this method and used to prepare the first reported polycarbonate with hexafluoroisopropoxy groups -C(CF3)2O- incorporated in the main chain via polycondensation. Polysilyl ethers were also prepared from this diol. Additionally, we briefly mention Carraher's legacy in the synthesis of metal-containing polymers via reactions of group IVB metallocene dichloride with dinucleophiles (diamines, diol, dicarboxylic acids, and dithiols) in solution and interfacial conditions in terms of electrophilic vs nucleophilic polycondensation. The new acidic, sterically hindered semi-fluorinated diol and bisphenol AF were reacted with group IVB metallocene dichloride in attempts to form metallocene condensation polymers with improved solubility.