Effect of Residual Swelling Solvent on Nanopore Formation in Replication of Swollen Hydrogel Network
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.
KeywordsHydrogel Nanoscopic network Replication Residual water Pore size distribution Water robe
The authors gratefully acknowledge the continuous financial support and many useful suggestions by Hitachi Chemical Co. Ltd.
- 1.Tan C, Lu R, Xue P, Bao C, Zhao Y (2008) Mater Chem Phys in pressGoogle Scholar
- 2.Lopez-Ureta LC, Orozco-Guareño E, Cruz-Barba LE, Gonzalez-Alvarez A, Bautista-Rico F (2008) J Polym Sci, Part A: Polym Chem 46:2667Google Scholar
- 3.Fu XJ, Wang NX, Zhang SZ, Wang H, Yang YJ (2008) Wuji Cailiao Xuebao (Journal of Inorganic Materials) 23:393Google Scholar
- 4.Ford J, Yang S (2007) Chem. Mater. 19:5570Google Scholar