Formation Of Nanostructures In Thermosets Via Reaction-Induced Microphase Separation

The morphological control of thermosets at the nanometer level is long a pursuit in the studies of polymer materials; the formation of nanostructures in thermosets can further optimize the properties of materials. It is crucial to understand the formation mechanisms of nanostructures in thermosets for controlling the morphology to obtain the improved properties of the materials. de Gennes ever proposed that ordered nanostructures of thermosets can be formed via locking-in preformed ordered mesoscopic structures of thermosets precursors via polymerization (i.e., crosslinking). More recently, Bates et al. proposed a novel strategy of creating the nanostructures in thermosets using amphiphilic block copolymers. In the protocol, precursors of thermosets act as selective solvents of block copolymers and some self-assembly morphology such as lamellar, bicontinuous, cylindrical, and spherical structures are formed in the mixtures depending on blend composition before curing reaction. The micelle structures can be fixed with adding hardeners and subsequent curing. The prerequisite for the self-assembly approach is that block copolymers are self-organized into micelle structures in their mixtures with precursors of thermosets prior to curing. Nonetheless, this case does not always occur since in many circumstances all the subchains of block copolymers are miscible with the precursors of thermosets. The miscibility (or solubility) is ascribed to the negligible entropic contribution (?Sm) to free energy of mixing (?Gm) in the mixtures of block copolymers and the low molecular compounds (viz. precursor of thermosets). In addition, the presence of the self-organized microphases formed at lower temperatures does not purport the survival of the structures at elevated temperatures that are required for curing of...