Abstract Highly porous and nanostructured pectin aerogels were synthesized via dissolution-solvent exchange-drying with supercritical CO2. The goal was to show why and how aerogel morphology and properties vary as a function of external conditions. Polymer concentration, pH and concentration of mono- and divalent metal salts were varied. The way of structure stabilization, i.e. gelation or direct non-solvent induced phase separation (in other words, the state of the matter before solvent exchange, gel or solution) turned out to be one of the key parameters influencing aerogel morphology and density. When strong gels were formed via calcium-induced gelation at pH around pKa, the corresponding aerogels presented large pores, the lowest density (0.04–0.05 g/cm3) and lowest specific surface area (around 270–350 m2/g). On the contrary, when pectin network was formed via non-solvent induced phase separation from non-gelled pectin solutions during solvent exchange step, the resulting aerogels were mesoporous, with highest density (0.12–0.15 g/cm3) and highest specific surface area (around 600 m2/g). The results obtained provide the guidelines for making aerogel matrices with fully controlled morphology and properties.

中文翻译：

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调整果胶气凝胶的结构和性能

摘要 通过溶解-溶剂交换-超临界二氧化碳干燥合成了高度多孔和纳米结构的果胶气凝胶。目标是展示气凝胶形态和性质为何以及如何随外部条件而变化。聚合物浓度、pH 值和一价和二价金属盐的浓度是变化的。结构稳定的方式，即凝胶化或直接非溶剂诱导相分离（换句话说，溶剂交换前的物质状态、凝胶或溶液）被证明是影响气凝胶形态和密度的关键参数之一。当通过钙诱导凝胶在 pKa 附近形成强凝胶时，相应的气凝胶呈现出大孔、最低密度（0.04-0.05 g/cm3）和最低比表面积（约 270-350 m2/g）。相反，当在溶剂交换步骤中通过非溶剂诱导与非凝胶果胶溶液的相分离形成果胶网络时，所得气凝胶是介孔的，具有最高的密度（0.12-0.15 g/cm3）和最高的比表面积（约 600 m2/ G）。获得的结果为制备具有完全受控的形态和性质的气凝胶基质提供了指导。