Enthalpy-driven ring-opening polymerization of highly strained macrocyclic biaryl-ether-ketones

Colquhoun, H.M., Zhu, Z.X. and Dudman, C.C. (2005) Enthalpy-driven ring-opening polymerization of highly strained macrocyclic biaryl-ether-ketones. Macromolecules, 38 (25). pp. 10421-10428. ISSN 0024-9297 doi: 10.1021/ma051781x

Abstract/Summary

Highly strained macrocyclic ether-ketones obtained by nickel-catalyzed cyclization of linear precursor oligomers undergo ring-opening polyinerization via ether exchange in the presence of nucleophilic initiators such as fluoride or phenoxide anions. Strain enthapies of these macrocycles, from DSC analyses of their exothermic ring-opening polymerization are in the range 50-90 kJ mol(-1). Melt-phase polymerization generally affords slightly cross-linked materials, but solution-phase polymerization at high macrocycle concentrations gives fully soluble, high molar mass polymers with inherent viscosities of up to 1.78 dL g(-1). Sequence-analysis of the resulting polymers by C-13 NMR shows that alternating or random monomer sequences may be obtained, depending on whether one or both aromatic rings adjacent to the ether linkages are activated toward nucleophilic attack.