Hydrophobic corn starch thermoplastic films produced by plasma treatment

Polymer coating technology is currently an important field in science as it can lead to final products with enhanced characteristics characterized by desired bulk and surface properties. Low power plasmas can induce the polymerization of a precursor gas on the substrate surface as well as introduce functional groups under specific plasma conditions. In the present work, we studied the possibility of reducing water sensitivity of corn starch films by sulfur hexafluoride (SF6) plasma treatment. Confocal laser microscopy as well as atomic force microscopy was used to observe the main surface modifications and results indicated starch cross-linking. Fluoride was incorporated to the surface and the relationship between fluoride and sulfur incorporation to the surface was very much dependent on plasma power. Results indicate that fluoride could be preferentially incorporated on polymeric surfaces at −100 V self-bias and the overall surface morphology determined the measured contact angle. The dynamic behavior of surface contact angle was observed to be very much dependent on the treatment time and force–distance curves were used to further characterize the chemical surface modifications locally. Optimized treatment conditions led to water contact angles up to 130°. Even after being in contact with water for 10 min, surfaces remained hydrophobic, presenting contact angles over 100°.