Solvents, CO2 and biopolymers: Structure formation in chitosan aerogel
Solvents, CO2 and biopolymers: Structure formation in chitosan aerogel
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溶剂、二氧化碳和生物聚合物：壳聚糖气凝胶的结构形成
DOI：
10.1016/j.carbpol.2020.116680
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发表时间：
2020
影响因子：
11.2
通讯作者：
W. J. Malfait
中科院分区：
文献类型：
--
作者：
S. Takeshita;A. Sadeghpour;D. Sivaraman;S. Zhao;W. J. Malfait
生物聚合物气凝胶的功能本质上与其微观结构有关，而微观结构又取决于合成方案。对壳聚糖气凝胶合成过程中宏观尺寸变化和纳米结构形成的详细研究揭示了生物聚合物气凝胶提高工艺灵活性的新方面。甲醛交联壳聚糖凝胶在溶剂交换为甲醇 (50.3%)、乙醇 (47.1%) 或异丙醇 (26.7%) 后保留了其原始体积的很大一部分，但在随后的超临界 CO2 处理过程中急剧收缩（分别降至 4.9%、3.5% 和 3.7%）。相比之下，壳聚糖凝胶在交换到庚烷（7.2%）（一种低亲和力溶剂）后收缩得更强烈，并在二氧化碳处理过程中保持这个体积。小角度X射线散射证实体积变化的发生与通过CO 2 或庚烷中的物理凝固形成的中孔网络形成相关。结构形成步骤可以通过溶剂-聚合物和聚合物-干燥相互作用来控制，这将是定制气凝胶结构的新工具。
The functionality of biopolymer aerogels is inherently linked to its microstructure, which in turn depends on the synthesis protocol. Detailed investigations on the macroscopic size change and nanostructure formation during chitosan aerogel synthesis reveal a new aspect of biopolymer aerogels that increases process flexibility. Formaldehyde-cross-linked chitosan gels retain a significant fraction of their original volume after solvent exchange into methanol (50.3 %), ethanol (47.1 %) or isopropanol (26.7 %), but shrink dramatically during subsequent supercritical CO2processing (down to 4.9 %, 3.5 % and 3.7 %, respectively). In contrast, chitosan gels shrink more strongly upon exchange inton-heptane (7.2 %), a low affinity solvent, and retain this volume during CO2processing. Small-angle X-ray scattering confirms that the occurrence of the volumetric changes correlates with mesoporous network formation through physical coagulation in CO2orn-heptane. The structure formation step can be controlled by solvent–polymer and polymer–drying interactions, which would be a new tool to tailor the aerogel structure.