Functionalization of nano-objects in living anionic polymerization-induced self-assembly and their use for improving thermal properties of epoxy resins

Abstract

Nano-objects generated via a scalable polymerization-induced self-assembly (PISA) process can serve as organic nanofillers, replacing the widely used inorganic nanofillers in composites. In this contribution, polyisoprene (PI)-b-polystyrene (PS) (PI-b-PS) or PI-b-PS/PS nano-objects were prepared via a living anionic polymerization-induced self-assembly (LAPISA) process or a derived process of living anionic polymerization-induced cooperative assembly (LAPICA) using nonpolar n-heptane as a solvent, which facilitated the control over morphologies and sizes. After the living species in the core region were in situ crosslinked by divinylbenzene (DVB) monomers, stabilized PDVB@(PI-b-PS) or PDVB@(PI-b-PS/PS) nano-objects were generated. After hydroxylated or epoxidized nano-objects were obtained through thiol–ene or epoxidation reactions on the double bonds of the PI stabilizer, the miscibility between the nano-objects and epoxy resin was improved, and the functionalized nano-objects could be introduced into epoxy resin. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and thermomechanical analysis (TMA) results affirmed that the organic nano-objects could improve the thermal properties of the composites, which were obviously superior to commercial inorganic silica nano-objects. In particular, the composites with smaller spherical nano-objects had a higher glass transition temperature (T_g) than those with larger spherical ones or worm-like ones. Transmission electron microscopy (TEM) measurements verified the uniform distribution of organic nano-objects and the formation of sufficiently integrated interfaces between the epoxy resin and nano-objects, thereby improving the thermal properties of the composites.