Toughening of epoxy thermosets by self-assembled nanostructures of amphiphilic comb-like random copolymers

• Published in: RSC advances Vol. 13; no. 47; pp. 33484 - 33494
• Main Authors: Jheng, Li-Cheng, Chang, Ting-Yu, Fan, Chin-Ting, Hsieh, Tsung-Han, Hsieh, Feng-Ming, Huang, Wan-Ju
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 07.11.2023
• Subjects: Addition polymerization; Copolymers; Fracture toughness; Glass transition temperature; Micelles; Modulus of elasticity; Nanostructure; Polyethylene glycol; Polymer blends; Polymers; Self-assembly; Strain energy release rate; Stress intensity factors
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d3ra06349f

Amphiphilic comb-like random copolymers synthesized from poly(ethylene glycol) methyl ether methacrylate (PEGMMA) and stearyl methacrylate (SMA) with PEGMMA contents ranging between 30 wt% and 25 wt% were demonstrated to self-assemble into various well-defined nanostructures, including spherical micelles, wormlike micelles, and vesicle-like nanodomains, in anhydride-cured epoxy thermosets. In addition, the polymer blends of the comb-like random copolymer and poly(stearyl methacrylate) were prepared and incorporated into epoxy thermosets to form irregularly shaped nanodomains. Our research findings indicate that both the comb-like random copolymers and polymer blends are suitable as toughening modifiers for epoxy. When added at a concentration of 5 wt%, both types of modifiers lead to substantial improvements in the tensile toughness (>289%) and fracture toughness of epoxy thermosets, with minor reductions in their elastic modulus (<16%) and glass transition temperature (<6.1 °C). The fracture toughness evaluated in terms of the critical stress intensity factor ( K IC ) and the strain energy release rate ( G IC ) increased by more than 67% and 131% for the modified epoxy thermosets containing comb-like random copolymers. Amphiphilic comb-like random copolymers bearing epoxy-philic PEGMMA and epoxy-phobic alkyl pendants can self-assemble into well-defined nanostructures in anhydride-cured epoxy thermosets.