Effect of Residual Swelling Solvent on Nanopore Formation in Replication of Swollen Hydrogel Network
Effect of Residual Swelling Solvent on Nanopore Formation in Replication of Swollen Hydrogel Network
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DOI：
10.1007/978-3-642-00865-8_16
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
K. Kurumada;A. Suzuki;E. Otsuka;Susumu Baba;Youhei Seto;Keisuke Morita;Takanori Nakamura
中科院分区：
文献类型：
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作者：
K. Kurumada;A. Suzuki;E. Otsuka;Susumu Baba;Youhei Seto;Keisuke Morita;Takanori Nakamura
在聚N，N′ -异丙基丙烯酰胺（PNIPAM）水凝胶和二氧化硅固化预成溶胶共存的条件下，将PNIPAM水凝胶网络复制到二氧化硅基体中。在干燥过程中，纳米网络结构逐渐固定在固化的二氧化硅基质中。干燥的条件被证明是高度影响的纳米孔的总体积和孔径分布。当在接近水的饱和蒸气压下进行干燥以延缓所含水的蒸发时，作为PNIPAM水凝胶的复制品的纳米孔的总体积和横截面直径显著大于在对空气开放的正常空气干燥的情况下的纳米孔的总体积和横截面直径。这一结果表明，残留的水包裹PNIPAM聚合物链作为“水长袍”，并且作为其结果，纳米孔的尺寸和总体积显著增加。纳米孔的形成体积与预成型件中的水含量的比较显示，在延迟干燥期间，超过一半的水蒸发了不可忽略的比例，而没有有助于纳米孔的形成。因此，只有在二氧化硅基质的整个固化阶段残留在PNIPAM和二氧化硅的混合物中的水才能起到增强纳米孔的作用。
Hydrogel network of poly N, N′ – isopropyl acrylamide (PNIPAM) was replicated into a silica matrix in the coexistence of PNIPAM hydrogel and solidifying preform sol of silica. During the drying process, the nanoscopic network structure was gradually immobilized in the solidifying silica matrix. The condition for the drying was shown to be highly influential on the total volume of the nanopore and pore size distribution. When the drying was carried out near the saturated vapor pressure of water in order to retard the evaporation of the contained water, the total volume and cross-sectional diameter of the nanopore as the replica of PNIPAM hydrogel were significantly larger than those in the case of normal air-drying open to air. This result indicates that the residual water enveloped PNIPAM polymer chains as a “water robe”, and as a result of that, the size and total volume of the nanopore significantly enhanced. The comparison of the formed volume of the nanopore to the water content in the preform revealed that a nonnegligible proportion over the half of the water evaporated during the retarded drying without contributing to the formation of the nanopore. Thus, only the water that remained in the hybrid of PNIPAM and silica at the stage of the entire solidification of the silica matrix could play the role of enhancing the nanopores.