Facile superhydrophobic modification on HPMC film using polydimethylsiloxane and starch granule coatings

The excessive water sensitivity of hydroxypropyl methylcellulose (HPMC) films prevent them from being used extensively. In order to overcome this limitation, superhydrophobic HPMC films were meticulously crafted through the utilization of a composite of polydimethylsiloxane (PDMS) and ball-milled rice starch, corn starch, or potato starch (RS/CS/PS) for the coating process. Initially possessing hydrophilic properties, the HPMC Film (CA = 49.3 ± 1.8°) underwent a transformative hydrophobic conversion upon the application of PDMS, resulting in a static contact angle measuring up to 103.4 ± 2.0°. Notably, the synergistic combination of PDMS-coated HPMC with ball-milled starch demonstrated exceptional superhydrophobic attributes. Particularly, the treated HPMC-based film, specifically the HP-CS-2 h film, showcased an impressive contact angle of 170.5° alongside a minimal sliding angle of 5.2°. The impact of diverse starch types and the ball milling treatment on the PDMS/starch coatings and HPMC film was thoroughly examined using scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXS), and particle size analysis. These studies demonstrated that the low surface energy and roughness required for the creation of superhydrophobic HPMC-based films were imparted by the hierarchical structure formed by the application of PDMS/ball-milled starch. Polydimethylsiloxane (PubChem CID: 24764); Hydroxypropyl methylcellulose (PubChem CID: 671); Ethyl acetate (PubChem CID: 8857).