Aggregation behavior of alkoxide-derived silica in sol-gel process in presence of poly(ethylene oxide)

被引:78
作者
Takahashi, R [1 ]
Nakanishi, K [1 ]
Soga, N [1 ]
机构
[1] Kyoto Univ, Grad Sch Engn, Dept Chem Mat, Sakyo Ku, Kyoto 6068501, Japan
关键词
organic-inorganic interaction; in situ observation of sol-gel reaction; phase separation; meso scale structure;
D O I
10.1023/A:1008753718586
中图分类号
TQ174 [陶瓷工业]; TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
Growth behavior of silica in an acid catalyzed sol-gel process from silicon alkoxide in the presence of poly(ethylene oxide), PEO, was investigated by in situ small angle X-ray scattering, SAXS, and Si-29 NMR measurements. The results of SAXS, that aggregation and gel formation behaviors of silica were affected by the presence of PEO, suggested a strong attractive interaction between silica oligomers and PEO. A possible reaction scheme of silica in the presence of PEO is as follows; (1) PEO and small silica oligomers coexist in the solution without specific interaction just after hydrolysis of the silicon alkoxide. (2) With the progress of condensation, a ramified aggregated complex between PEO and silica oligomers is formed, which is characterized by larger apparent value of radius of gyration and smaller fractal dimension than in the PEO-free system. (3) After gelation, the fractal dimension of scatterers remains to be smaller than that in the PEO-free system, because PEO associated with the silica network inhibits aggregation within the gel networks. Furthermore, PEO inhibits the condensation in the aging and in the drying process, leading to less strongly crosslinked dry gel. A temporal maximum in the time evolution of R-g was observed for the samples separated into two phases with their characteristic domain size being larger than several micrometers. This is considered to be a phenomenon related to increase and divergence of correlation length near and at the critical point.
引用
收藏
页码:7 / 18
页数:12
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