Pseudorotaxanes of Cyclodextrin and Diglycidyl Ether of Bisphenol A as Precursors of New Intramolecularly Reinforced Epoxy-based Thermosets

As a preliminary work in the search of potential monomers for new intramolecularly reinforced epoxy-based materials, this investigation has been aimed at the synthesis and the physico-chemical characterisation of the monomers formed by complexation between β- and γ-cyclodextrin (CD) and diglycidyl ether of bisphenol A (DGEBA). Results from steady-state fluorescence suggest that, even at high temperature, the DGEBA forms very stable complexes with both macrocycles (particularly with the β-CD) in aqueous solution. Regardless of the CD and according to the interproton distances obtained from the ROESY spectrum when compared with the simulated ones by semi-rigid docking, the oxirane ring of the DGEBA monomer can be found outside the cavity, while the bisphenol moiety firmly remains attached and buried in the CD. The stability of the adduct and the lack of steric hindrance at the epoxide functional points, make the complex very interesting for the synthesis of crosslinked epoxy based polymers, in which the bisphenol part would be covered and therefore protected by the CD. The semi-rigid docking scheme applied to this host–guest system reveals itself as a useful tool for the search of conformers that fit the experimental distances obtained by NMR, although its utility for the estimation of the free energies of binding is still limited.