Macroporous Polymers with Interconnectivity Gradients: Photopolymerization of Emulsion Templates Controlled by Height-Dependent Light Intensity

Abstract

Gradient porous polymers are engineered to vary the pore size, porosity, and interconnectivity in a single direction, enabling controlled mass transport and mechanical properties. This unique design makes them ideal candidates for applications in tissue engineering scaffolds, advanced filtration systems, and absorbent materials for environmental remediation. While various methods have been developed to create porous polymers with gradients in pore size and porosity, techniques for generating openness gradients remain largely unexplored. In this study, we present a novel approach for producing porous materials with a gradient openness through the photopolymerization of emulsion templates. By modulating the light intensity across the height of the emulsion templates during the photopolymerization process, we induce a gradual change in openness within polymerized high internal phase emulsions (polyHIPEs). This effect arises from the interplay between interfacial and bulk polymerization, influenced by the partitioning behavior of photoinitiators in the continuous phase, light intensity, and distance from the light source. Stronger light sources enhance the openness and produce more pronounced openness gradients. The progressive attenuation of light within the emulsion templates is primarily governed by UV transparency, which is controlled by incorporating different radical monomers, such as acrylic acid and acrylamide. This single-step process allows for the fabrication of porous polymers with precisely tuned mass transfer properties through controlled interconnectivity gradients.