The preparation of SiO2-PMMA sol and the procedure for fabricating composite coatings on SS was adopted from our previous report [25]. The experimental stages are illustrated in Scheme 1. Shortly, 2 ml of double distilled water and 1 ml of ammonia solution was added to 20 ml of ethanol under constant stirring. After 1 h of stirring, 2 ml of MTMS was added drop-wise into it and the mixture was stirred for another 3 h. Meanwhile, a 10 mgml−1 of PMMA solution in DMF was prepared. 6 vol% of PMMA in the above prepared SiO2 sol were prepared and kept stirring overnight. The pre-cleaned glass substrates were dip-coated with a dipping rate of 5 mms−1 and withdrawal rate of 2 mms−1. The deposition time was varied from 10, 20, 30 and 45 min. All these experiments were carried out at room temperature (25 °C). Finally, the dip-coated substrates were dried at room temperature for 1 h and annealed at 250 °C overnight with a ramping rate of 2 °C min−1.