中文摘要：

用密度泛函方法在B3LYP/6-31G（d,p）基组水平上对反应系统中的所有物种进行全优化,用CPCM溶剂模型在同一基组水平上进行了单点计算,系统研究了硅醇盐前驱体Si（OCH3）4在酸性条件下的水解、聚合机理,阐明了二者的相互竞争关系.研究发现,H2O以氢键或配位键与前驱体结合,然后通过氢转移完成水解;水分子从质子化烷氧基的对面键合并发生水解;第4级水解是H2O从对位驱逐质子化烷氧基,但不能水解完全;水解产物通过＂环状模式＂,由氢键结合成多元环,然后发生氢转移并完成聚合;水解过程的能垒明显低于聚合过程;H＋阻止水解产物聚合成环;硅正离子可引发无垒聚合反应,但在能量上并不可行.

英文摘要：

All species in this reaction system were fully optimized at B3LYP/6-31G（d,p） basis set level by using density functional theory,and then single point energy calculations were performed.In succession the hydrolysis and oligomerization mechanisms of Si（OCH3）4 in acidic solutions were investigated systematically to elucidate the competitiveness between hydrolysis and oligomerization.This theoretical model show that：（1） H2O is bonded to precursors via hydrogen bonds or coordination bonds to facilitate hydrolysis;（2） H2O attacks precursors from the opposite side of protonated alkoxy groups;（3） for the fourth-order hydrolysis,H2O expels protonated alkoxy groups from the opposite side,but the precursor does not hydrolyze completely;（4） the hydrolysis products condense via the ＂ring mode＂,viz. the hydrolysis products are linked together via hydrogen bonds to form polyatomic rings to oligomerize via hydrogen transfer;（5） the precursor Si（OCH3）4 is inclined to hydrolyze than to condense;（6） proton blocks the cationic dimers to cyclize;（7） silicon cation can solicit non-barrier oligomerization,but the ionic reaction channels are energetically unfavorable.