Tailoring doubly porous poly(2-hydroxyethyl methacrylate)-based materials via thermally induced phase separation

- Doubly porous PHEMA-based materials are generated by an original route via thermally induced phase separation.
- Varying PHEMA concentrations are used with water/1,4-dioxane to induce the TIPS process at different quenching temperatures.
- A lower quenching temperature is generally associated with smaller macropore sizes and larger nanopore sizes.
- The water/1,4-dioxane volume ratio is critical to produce biporous structures, as water favors the formation of nanopores.
- Polymer concentration has a significant influence on the morphology of biporous frameworks, essentially on the nanoporosity.

This original report addresses an innovative concept for generating doubly porous poly(2-hydroxyethyl methacrylate) (PHEMA)-based materials via thermally induced phase separation (TIPS). A co-solvent mixture constituted of water and 1,4-dioxane was used to solubilize linear PHEMA chains, followed by a solidification process by quenching the PHEMA/co-solvent mixture at a given temperature, and subsequent freeze-drying to produce the corresponding biporous PHEMA materials. Critical physico-chemical parameters, such as the quenching temperature, the co-solvent volume ratio, and the polymer concentration, were carefully investigated to clearly understand their effects on pore size and morphology. Anisotropic macropores with a tubular shape in the 10-100 μm size range were generally obtained, along with various nanoporous structures within the macropore walls. One such lower porosity level displayed pore sizes ranging from about 40 nm to 800 nm, depending on the parameters used to fabricate the doubly porous frameworks. The possibility of cross-linking the porous materials engineered by TIPS was finally examined by taking advantage of the reaction between hydroxyl groups of PHEMA with different acyl dichlorides, which could pave the way for further potential applications in the biomedical area.

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