Transparent superhydrophobic hollow films (TSHFs) with superior thermal stability and moisture resistance

Highly transparent superhydrophobic hollow films (contact angle, 165.7 degrees and sliding angle, 2.1 degrees) have been prepared by using candle soot as a template, followed by methyltrimethoxysilane (MTMS) chemical vapor depostion (CVD) and calcination at 450 degrees C, without the addition of dibutyl tin laurate (DBTL). The influence of deposition time on the superhydrophobicity and transparency of the as-prepared films was discussed herein to get the optimum performance film. The film shows high transparency (transmittance close to 90%) when it was coated on a glass substrate. What is more, it shows good thermal stability and superior moisture resistance as well, retaining its superhydrophobicity after calcining up to 500 degrees C or even exposure to ambient conditions for 30 days. 29Si NMR, XPS spectra and thermal analysis verify the existence of methyl groups linked with silicon matrix on film (low surface energy), while AFM and TEM analysis confirm the sub-100 nm roughness and hollow structure of the optimum film.