Influence of sonication on the morphology and mechanical properties of methyl methacrylate based PolyHIPE monoliths

Abstract

The morphology of polyHIPE materials directly governs their permeability, surface area, and mechanical properties, therefore developing novel strategies to enhance emulsion uniformity and influencing the droplet size is crucial for advancing their practical applications. Methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) containing high internal phase emulsions (HIPEs) with internal phase volume fractions between 75% and 85% were prepared using a surfactant and homogenized with an overhead stirrer. Following emulsification, the HIPEs were either directly photopolymerised or first subjected to ultrasonic treatment and then photopolymerised. All resulting materials exhibited characteristic polyHIPE morphologies, comprising highly porous, interconnected structures. The primary pore diameters typically ranged from 3 to 23 μm. In all cases, ultrasound treatment resulted in a substantial reduction in average pore size, with decreases ranging from 10% to 50%, depending on the formulation. Morphological changes are attributed to acoustic cavitation and enhanced droplet disruption during sonication, confirming the influence of ultrasound on emulsion structure and the resulting pore architecture. Furthermore, compression testing showed that the improved pore uniformity introduced by sonication influences mechanical properties, resulting in higher compressive strength and increased elasticity compared to non-sonicated samples of the same composition.