Hyperbranched polymers containing epoxy and imide structure

A challenge to polymer scientists is to design new materials with superior overall performance in heat-resistance, cold-resistance, strength, and toughness. Here we report the synthesis of hyperbranched polymers containing epoxy and imide structure (EHPI-n, n = 6, 12, and 24) with various molecular weights and degrees of branching using a new synthetic diimide dicarboxylic acid. EHPI-n significantly decreases the gelation time and accelerates the curing of EHPI-n/diglycidyl ether of bisphenol-A (DGEBA). Both EHPI-6 and EHPI-12 significantly reduce the viscosity, activation energy, and average particle size of EHPI-n/DGEBA blends due to the disentangling function and compatibility of the EHPI-n. The toughness property, including elongation at break, impact strength, critical strain energy value (GIC) and critical stress intensity factor (KIC) of 12 wt % EHPI-12/DGEBA composites are improved over the neat DGEBA, by 144.72 %, 197.9 %, 168.4 % and 72.6 %, respectively, while their mechanical properties, including tensile strength, storage modulus and flexural strength are enhanced by 61.2 %, 89.9 %, 44.2 %. The heat-resistant index and β-relaxation peak temperatures of the composites are improved 14 °C and 15 °C, respectively, indicating both outstanding high-temperature resistance and outstanding low-temperature resistance. The simultaneous improvement on multiple performances is attributable to an in-situ homogeneous reinforcing and toughening mechanism, which is explained by free volume fraction, microstructure and surface micrograph. The EHPI-n present great potential as advanced materials for aerospace and wind turbine.