Hyperbranched polyether as an all-purpose epoxy modifier: controlled synthesis and toughening mechanisms

The facile controlled synthesis of an epoxide-terminated hyperbranched aromatic polyether (EHBPE) that is suitable for mass production is demonstrated using a one-pot A(2) + B-3 approach by taking advantage of competing reactions. When used as toughener for the DGEBA/TETA curing system, non-phase-separated hybrids with notable improvements in toughness are obtained. Moreover, the addition of EHBPE also simultaneously improves the glass transition temperature (T-g) and tensile strength. T-g, tensile strength, impact strength, glassy modulus, and fractional free volume are found to increase with EHBPE loading up to 10%. Explanations for the three enhancements are provided. More importantly, the toughening mechanisms for the non-phase-separated hybrids are outlined in detail for the first time.