Heitz C, Laurent G, Briard R, Barthel E
Surface du Verre et Interfaces, Laboratoire Mixte CNRS/Saint-Gobain, Saint-Gobain Recherche, 39, quai Lucien Lefranc, 93303 Aubervilliers Cedex, France.
J Colloid Interface Sci. 2006 Jun 1;298(1):192-201. doi: 10.1016/j.jcis.2005.12.011. Epub 2006 Feb 7.
We have observed the condensation of a mixture of gamma-glycidoxypropylmethyldiethoxysilane and 3-aminopropyltriethoxysilane in dilute aqueous solutions. NMR and IR spectroscopy have allowed to follow the condensation process in the mixture, which is noticeably enhanced and proceeds faster than for each silane on its own. Cross-condensation between the two silanes was evidenced. When the hydrophilic aminosilane is in excess, the condensation, as evidenced by dynamic light scattering, proceeds toward gel formation because the oligomers formed are essentially hydrophilic. When the more hydrophobic epoxysilane is in excess, oligomer growth proceeds slowly and results in a destabilization of the solution: due to their hydrophobic character, the oligomers formed coalesce suddenly into 200-nm-diameter aggregates. Coatings deposited from such solutions with high epoxysilane content can be used to strengthen glass. We show that the progress of condensation in solution results in a wetting transition during deposition of the silane film on glass by dip coating. The production of increasingly hydrophobic oligomers as the reaction time increases results in adsorption of more hydrophobic aggregates at the surface, which eventually leads to dewetting of the film: in the absence of film, glass strengthening disappears.
我们观察了γ-缩水甘油醚氧丙基甲基二乙氧基硅烷和3-氨丙基三乙氧基硅烷的混合物在稀水溶液中的缩合反应。核磁共振（NMR）和红外光谱（IR）使我们能够跟踪混合物中的缩合过程，该过程明显增强，并且比每种硅烷单独进行时更快。两种硅烷之间的交叉缩合得到了证实。当亲水性氨基硅烷过量时，如动态光散射所证明的，缩合反应朝着凝胶形成的方向进行，因为形成的低聚物基本上是亲水性的。当疏水性更强的环氧硅烷过量时，低聚物生长缓慢，导致溶液不稳定：由于其疏水性，形成的低聚物会突然聚结成直径为200纳米的聚集体。用这种环氧硅烷含量高的溶液沉积的涂层可用于强化玻璃。我们表明，溶液中缩合反应的进行导致在通过浸涂将硅烷膜沉积在玻璃上的过程中发生润湿转变。随着反应时间的增加，越来越疏水的低聚物的产生导致更多疏水聚集体吸附在表面，最终导致膜的去湿：在没有膜的情况下，玻璃强化消失。
