Selective homopolymerization of cyclohexene oxide catalyzed by hexafluorophosphate salts

The peculiar reactivity of hexafluorophosphate salts as perfectly selective catalysts for the production of poly(cyclohexene oxide) (PCHO) is here reported. Indeed, notwithstanding their substantial inability to bind a five-coordinated metal center to give rise to an octahedral molecule active in the epoxide ring opening, the R3PX+ PF6- salts have been tested are able to initiate and carry on the homopolymerization of CHO to PCHO in almost every experimental condition. Several experiments, performed both in presence or absence of a metal Salen-type catalyst and/or under pressure, selectively led to the unique formation of pure polyether with no byproducts when cyclohexene oxide (CHO) was used as a monomer, with obtained homopolymers revealing very similar properties despite the different cations, with the cation-bound halide being reasonably disregarded as initiator. On the contrary, the use of propylene oxide (PO) as a monomer does not allow this characteristic reactivity, leading back to the performance already reported for B+X- cocatalysts1-3. FTIR/ATR, 1H-NMR, SEC and DSC studies on the afforded homopolymers were accomplished.