Photopatterning of Hierarchical Porous Polymers via Flash-Freezing and Polymerization-Induced Phase Separation

High Resolution Image Download MS PowerPoint Slide Hierarchical porous polymers with multiscale porosity have been widely investigated in various fields due to their enhanced diffusion and selective adsorption capabilities. This study develops a hybrid strategy that combines photopolymerization-induced phase separation (photo-PIPS) with flash-freezing to generate hierarchical porous structures composed of polystyrene (PS). A resin containing PS, 1,6-hexanediol diacrylate (HDDA), and methacrylic anhydride (MAA) in N, N -dimethylformamide (DMF) was photocured to form a semi-interpenetrating polymer network (semi-IPN) with linear PS and cross-linked acrylate network. The addition of PS led to photo-PIPS that generated macropores. The semi-IPN was immersed in −80 °C methanol for the flash-freezing process, which induced microphase separation and promoted the formation of PS nanofibers. We found that the cross-linking density and the compatibility of the photocurable monomers with PS mainly governed the extent of macropores formed during photo-PIPS. To enhance the accessible surface area, alkaline hydrolysis was applied to selectively remove the MAA-derived cross-linked network, thereby increasing the surface area of hierarchical porous PS. Moreover, selective photocuring through masks enabled the fabrication of spatially patterned porous structures. The above results demonstrate the potential of integrating flash-freezing and other pore-formation methods to shape hierarchical porous polymers.