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本文采取~(29)Si-核磁共振谱方法研究了在稀 HC1中水解 Si(OCH_3)_4所制取的单硅酸的缩合反应。其结果表明,作为较长时间放置稳定的初级缩合物,不是生成二硅酸,而是生成环三硅酸。进一步的缩合过程是通过单环或多环硅酸形成支链和交联的高分子产物。研究了缩合反应动力学对 SiO_2浓度与 pH 值的依赖关系,讨论了缩合机理,特别是低分子范围内的缩合机理。
In this paper, ~ (29) Si-NMR was used to study the condensation reaction of monosilicic acid prepared by hydrolyzing Si (OCH_3) _4 in dilute HC1. The results showed that instead of generating disilicate, a cyclic trisilicate was formed as a stable primary condensate for a longer period of time. A further condensation process is the formation of branched and crosslinked polymer products by monocyclic or polycyclic silicic acid. The dependence of condensation reaction kinetics on the concentration of SiO 2 and pH value was studied. The mechanism of condensation was discussed, especially the mechanism of condensation in the low molecular range.