Transparent hydrophobic organic–inorganic nanocomposite films

Hydrophobic, transparent organic–inorganic hybrid coatings were synthesized by the incorporation of SiO2 nanoparticles in a matrix of 3-glycidoxypropyltrimethoxysilane (GPTS) and tetramethyl orthosilicate (TMOS) followed by overlaying isobutyltrimethoxysilane (IBTMS) film for enhanced hydrophobicity. Scanning probe microscopy, ellipsometry and contact angle measurements were used to study their morphology, thickness and surface properties. GPTS and TMOS sol with SiO2 nanoparticles resulted in rough but transparent surface of homogeneous monolayer of ∼40 nm. The rough surface mimicking lotus leaf was chemically modified with a layer of IBTMS resulting in the contact angle of nearly 130°. Morphology as well as contact angles were dependent on the thickness of IBTMS hydrophobic coating layer. Process of creating rough but transparent and durable layer loaded with SiO2 particles demonstrates the feasibility of meeting all three desired characteristics of transparency, durability and superhydrophobicity.