Tamon H, Ishizaka H
Department of Chemical Engineering, Kyoto University, Kyoto, 606-8501, Japan
J Colloid Interface Sci. 1998 Oct 15;206(2):577-582. doi: 10.1006/jcis.1998.5770.
RF aerogels were prepared by sol-gel polycondensation of resorcinol with formaldehyde in a slightly basic aqueous solution and supercritical drying with carbon dioxide. The aerogels were characterized by nitrogen adsorption and density measurements. A small-angle X-ray scattering (SAXS) technique was applied to the gelation process of RF hydrogels. The structure formation of the hydrogels during the sol-gel transition was revealed by applying Guinier and power-law equations to the SAXS data. At the initial stage of the synthesis of RF hydrogels, small clusters of ca 2 nm consisting of branched polymeric species formed, showing a mass fractal dimension. Then the clusters aggregated and formed particles of ca 3-6 nm. These particles showed a surface fractal dimension. The hydrogel structure was fixed by gelation and the particles grew to ca 4-7 nm. Finally their surface became smooth by aging. The influence of the amount of resorcinol, basic catalyst, and water used in the polycondensation on the porous structures of the aerogels was explained by the structure formation model proposed. Copyright 1998 Academic Press.
通过间苯二酚与甲醛在弱碱性水溶液中的溶胶 - 凝胶缩聚反应以及用二氧化碳进行超临界干燥来制备RF气凝胶。通过氮气吸附和密度测量对气凝胶进行表征。将小角X射线散射（SAXS）技术应用于RF水凝胶的凝胶化过程。通过将吉尼尔方程和幂律方程应用于SAXS数据，揭示了水凝胶在溶胶 - 凝胶转变过程中的结构形成。在RF水凝胶合成的初始阶段，形成了由支化聚合物物种组成的约2 nm的小簇，呈现出质量分形维数。然后这些簇聚集并形成约3 - 6 nm的颗粒。这些颗粒呈现出表面分形维数。水凝胶结构通过凝胶化固定，颗粒生长到约4 - 7 nm。最后，通过老化其表面变得光滑。所提出的结构形成模型解释了缩聚反应中使用的间苯二酚、碱性催化剂和水的量对气凝胶多孔结构的影响。版权所有1998年学术出版社。
