Tailoring the Microarchitecture and Mechanical Properties of Styrene‐Hexyl Methacrylate PolyHIPEs via Microfluidic Emulsion Templating

Microfluidic emulsion templating enables unmatched control over pore size and ordering in polymerised high internal phase emulsions (PolyHIPE), yet its adoption for hydrophobic, chemically aggressive monomers is limited by the poor solvent compatibility of common chip materials and the cost/fragility of glass devices. Here, we present a microfluidic platform based on tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride (THV) enabling direct production of monodisperse water-in-oil HIPEs. Using a fixed dispersed-phase fraction (Φd ≈ 85%), we fabricate PolyHIPEs from styrene (STY) and hexyl methacrylate (HM) and compare how the polymerization pathway drives the formation of open and closed pore foams. Quantitative metrics reveal that closed-cell foams exhibit significantly greater pore shape distortion despite comparable porosity. Compression testing demonstrates that STY-based foams achieve markedly higher stiffness and energy absorption than HM-based counterparts, and unexpectedly, closed-cell foams underperform open-cell foams when pore irregularity is pronounced, highlighting that mechanical response cannot be inferred from porosity alone. Motivated by the strong contrast between pure STY and HM, we further investigate intermediate STY/HM blends (75/25, 50/50, 25/75) to map the non-linear transition in morphology and mechanics between glassy and compliant networks. Overall, this work demonstrates a microfluidic approach for engineering structure-chemistry-mechanics relationships in monodisperse hydrophobic PolyHIPEs using industrially relevant monomers.