Preparation and Characterization of Starch-Based Macroporous Materials by High Internal Phase Emulsion Templating Method

Liquid or supercritical carbon dioxide (LCO₂ or sc-CO₂) is an alternative green solvent to coventional organic solvents because of its nontoxic, non-flammable, and non-expensive, characteristics to prepare the CO₂-in-water high internal phase emulsion (C/W HIPEs, the internal phase volume fraction ≥ 74.05%). The C/W HIPEs emulsion can be used to produce the macroporous materials with special construction by the emulsion-templating polymerization method. Using this method, a novel starch-based macroporous material was produced. Firstly, the starch-based macromolecular monomer (S-MA) was synthesized by esterifying the soluble starch with methacrylic anhydride, and its structure was characterized by ¹H-NMR and FT-IR. Then the C/W HIPEs emulsion was prepared using poly(vinyl alcohol)-1788 as the surfactant, CO₂ as the internal phase, and S-MA solution as the continuous phase. The stability of emulsion was also investigated. The results indicated that the C/W HIPEs emulsion was stable for more than 24 h, whether or not S-MA in presence, even if the internal phase volume fraction took up to 90% and the surfactant mass concentration was as low as 2×10^-3 g/mL. Good stability of HIPEs was necessary to get macroporous materials for the following polymerization of the continuous phase. After the continuous phase was polymerized using the potassium persulfate/N, N, N', N'-tetramethylethylenediamine as the redox initiation system, starch-based macroporous materials with uniform monolithic materials in the cylindrical interior of the cell were recovered, suggesting no significant shrinkage after the CO₂ venting. SEM analysis shows that pore-size of these macroporous materials is above 10 μm with open-cell morphology, and these pores can be controlled easily by changing the volume ratio of internal phase and the continuous phase. These simple structure features of these materials supported cell growth and proliferation for tissue engineering applications.