Synthesis and Application of PES–PEEK Multiblock Copolymer in Toughening Epoxy Resin: Optimal Balancing Heat Resistance, Stiffness, and Toughness

Abstract

Epoxy resin is confronted with the trade-off among high heat resistance, high modulus, and good toughness. In order to address the challenge, a series of poly(ether sulfone)-polyetheretherketone multi-block copolymers (PEbPK) are synthesized with hydroxyl-terminated poly(ether sulfone) and fluorine-terminated polyetheretherketone oligomers with different molecular weights as build-blocks. As a proof-of-concept, the PEbPKs are applied as modifiers to toughen bisphenol A epoxy (E51) with 4,4′-diaminodiphenyl sulfones as a hardener. Introducing rigid PEEK segments into flexible PES improves the thermal resistance and modulus of the epoxy composites and without at expanse of toughness. It is due to the inherent rigidity of the PEEK segments and the molecular-level microphase separation of the composites. Apart from PEbPK-5k/10k (PEbPK-xk/yk indicates that in a multiblock copolymer, the Mn of PES is x and the Mn of PEEK is y, with units in thousand Daltons), other variants gain prominently enhanced modulus and toughness. This PEbPK modification offers a strategy for developing high-performance epoxy composites.