Synthesis of a novel star-shaped polyethylene-co-polystyrene copolymer by using ATRP and click methods and investigation of its effects on mechanical thermal properties of epoxy resins

New well-defined star Tween-b-polystyrene (A 4 B 3 ) copolymer, linear methylated polyethylene glycol-b-polystyrene (AB) di-block copolymer, and linear polystyrene-b-polyethylene glycol-b-polystyrene (ABA) tri-block copolymer were synthesized by combination of ATRP and click reaction. The accomplishment of the synthesis sequence of di-, tri- and star block copolymers were investigated by FTIR, 1 H-NMR and GPC analyses. The synthesized block copolymers were used as the modifier for an epoxy resin matrix. The effects of amounts of the prepared block copolymers on the morphology and size of fabricated nanostructures were studied by SEM analysis. The results showed that the spherical nanostructures formed via the fabricated star copolymers had the smallest size when compared to those generated by the tri- and di-block copolymers. The addition of block copolymers to the epoxy resin resulted in an enhancement in thermomechanical properties, investigated by universal tensile tests for evaluating mechanical properties and differential scanning calorimetry (DSC) for evaluating thermal properties. Rheological, mechanical tests and DSC revealed that star-polyethylene glycol-b-polystyrene(A4B3)/epoxy resin formulation, possessing the smaller size of nanospheres, exhibited higher tensile strength, higher elongation at break, and better thermal properties than those of di- and tri-block copolymer/epoxy resin formulations.