Reactive and flexible graft polyesters with polydimethylsiloxane side chains as versatile tougheners for epoxies

A kind of epoxy-functionalized flexible graft polyesters containing pendant polydimethylsiloxane short chains (ADSE) as novel tougheners for epoxies were developed. The polyesters with varying compositions were synthesized using dodecanedioic acid and azelaic acid as diacids, diethylene glycol and a Y-shaped mono-terminal bis‑carbon hydroxyl polydimethylsiloxane (PDMS) as diols, and two epoxy compounds as capping agents. Chemical structure and crystallization property of ADSE were well characterized by 1 H NMR, FTIR, GPC and DSC. Viscosity testing revealed a higher content of PDMS resulted in a lower viscosity of ADSE. Polyester containing 50% of PDMS in diols (ADSE50) showed best toughening and strengthening performance for epoxies. The epoxy thermosets containing 2% of ADSE50 exhibited the maximum impact strength of 40.42 kJ/m 2 and tensile strength of 103.25 MPa, which increase of 94.14% and 34.21% compared with that of neat epoxy. The introduction of ADSE50 also increased the glass transition temperature ( T g ), initial thermal decomposition temperature, hydrophobicity and maintain high transparency of epoxy thermosets. The polyester of ADSE 50 was demonstrated to be a versatile toughener, capable of fabricating high-performance epoxy thermosets.