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 A2 + B3 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 (Tg) and tensile strength. Tg, 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.