Structural, morphological, wettability and thermal resistance properties of hydro-oleophobic thin films prepared by a wet chemical process

The structural properties of fluorine containing polymer compounds make them highly attractive materials for hydro-oleophobic applications. However, most of these exhibit low surface energy and poor adhesion on the substrates. In the present investigation, crack free, smooth and uniform thin films of poly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole]-co-tetrafluoroethylene (TFD-co-TFE) with good adhesion have been deposited by wet chemical spin-coating technique on polished AISI 440C steel substrates. The as-deposited films (xerogel films) have been subjected to annealing for 1 h at different temperatures ranging from 100 to 500 8C in an argon atmosphere. The size growth of the nano-hemispheres increased from 8 nmfor xerogel film to 28 nm for film annealed at 400 8C. It was found that as the annealing temperature increased from 100 to 400 8C, nanohemisphere- like structures were formed, which in turn have shown increase in the water contact angle from 1228 to 1478 and oil (peanut) contact angle from 858 to 968. No change in the water contact angle (1228) has been observed when the films deposited at room temperature were heated in air from 30 to 80 8C as well as exposed to steam for 8 days for 8 h/day indicating thermal stability of the film.