Preparation and Formation Mechanism of TEOS / OTMS Superhydrophobic Coating

Abstract

TEOS-OTMS sols were prepared by sol-gel method using tetraethyl orthosilicate (TEOS) and octyl trimethoxysilane (OTMS) as raw materials.Hydrophobic coatings were prepared on a smooth glass substrate and an etched glass substrate by one-step immersion method.The effects of hydrolysis time on the hydrophobicity and hardness of the coating were studied.The formation mechanisms of TEOS-OTMS sol and hydrophobic coating were proposed.Results showed that colloidal particles with SiO2 particles as the glue core and octylsilane as the cover could be prepared through TEOS-OTMS in-situ hydrolysis polymerization.And a low surface hydrophobic film modified by an octyl chain could take shape on the glass substrate.When TEOS was treated with pre-hydrolysis polymerization for 4 h and the TEOS-OTMS was treated with co-hydrolysis polymerization for 20 min,the hydrophobic angle of the coating reached (124.01±2.00)° and the pencil hardness reached 6 H.The result of an microstructure analysis by scanning electron microscope showed that the glass substrate was etched to form micro protrusions with a spacing of 6.36 nm and an average size of 16.75 nm,which enhanced the entanglement and aggregation of TEOS and OTMS,and pores of 150～200 nm formed in the coating.This “micro roughness”was the key to the formation of superhydrophobic coating,and the hydrophobic angle of the TEOS-OTMS coating reached (160.08±2.00)°.

Keywords

• superhydrophobic coating|otms|teos|silane membrane|sol-gel method