The Dual-Stage Reactivity of Silane Coupling Agents

Stage 1: Hydrolysis

Alkoxy groups convert to silanols in aqueous/media:

Si(OR')₃ + 3H₂O → Si(OH)₃ + 3R'OH

Stage 2: Condensation

With inorganic surfaces:

Si(OH)₃ + HO─M → Si─O─M + H₂O

Self-condensation (undesired):

2Si(OH)₃ → Si─O─Si + 3H₂O

Critical Factors:

pH optimum: 4–5 for amino silanes

Inhibition of premature condensation via ethanol/water ratio control