Poly(hydroxyether of bisphenol A)-block-polydimethylsiloxane alternating block copolymer and its nanostructured blends with epoxy resin

Mannich condensation was utilized to synthesize poly(hydroxyether of bisphenol A)-block-polydimethylsiloxane alternating block copolymer (PH-alt-PDMS). The polymerization between the phenolic hydroxyl-terminated oligo(hydroxyether of bisphenol A) and amino-terminated oligodimethylsiloxane with the defined lengths was carried out via the formation of benzoxazine ring linkages, which was mediated with paraformaldehyde. The alternating block copolymer was characterized by means of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). The block copolymer was incorporated to prepare nanostructured thermosetting blends. The nanostructures of the thermosetting blends were investigated by means of atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). The formation of the nanostructures in the thermosetting composites was judged to follow the self-assembly mechanism in terms of the difference in miscibility of PDMS and PH subchains with epoxy resin after and before curing reaction. The fracture toughness of the nanostructured blends was evaluated in terms of the measurement of stress field intensity factor (K-IC). It is noted that the epoxy resin was significantly toughened. (C) 2008 Elsevier Ltd. All rights reserved.