Effect of annealing temperature on antireflection property and water contact angle of fluorine-based hydrophobic films by a sol-gel technique

Crack-free and smooth surfaces of poly[4,5-difluoro 2,2-bis-(trifluoroinethyl)-1,3 dioxole]-co-tetrafluoroethylene (TFE-co-TFD) films have been deposited by sol-gel technique on polished AISI 440C steel and quartz substrates. The deposited films have been subjected to annealing at different temperatures ranging from 100 to 500 degreesC for 1 h in argon atmosphere. The as-deposited and annealed films (below 300 degreesC) on quartz have shown antireflection behaviour in the UV region. Surface properties of the films have been examined by employing scanning electron microscopy, energy dispersive X-ray analyser, for morphology and elemental composition. Adhesion strength failure was measured by scratch resistance test technique indicated good adhesion of the films on the substrate. It was found that as the annealing temperature increased from 100 to 400 degreesC, nanostructured sphere like balls were formed which in turn has shown increase in the contact angle for water from 122degrees to 247degrees. No change in the water contact angle (122degrees) has been observed when the films deposited at room temperature were heated in air from 30 to 80 degreesC indicating thermal stability of the coating. (C) 2004 Elsevier B.V. All rights reserved.