Isatin thiosemicarbazones promote honeycomb structure formation in spin-coated polymer films: concentration effect and release studies

Formation of ordered porous polymer films is one of the techniques currently under investigation for its potential for the manufacturing of coatings with biomedical applications. Aiming for films with improved characteristics against bacterial colonization, poly(methyl methacrylate) (PMMA) and polyurethane (PU) films were formed via the spin coating method on silica wafer (SW) substrates, in the absence or presence of four isatin thiosemicarbazone derivatives (ITSCs) in various concentrations. The resulting films exhibited high hydrophobicity based on contact angle goniometry measurements ranging from minimum water contact angle values of 84.0° ± 4.0 for PMMA and 85.0° ± 0.2 for PU, alone, to a maximum of 129.3° ± 2.6 and 102.1° ± 1.4, respectively, after the addition of an ITSC. Atomic force microscopy revealed rough polymer surfaces with honeycomb structures which are affected by ITSC type and concentration. PMMA films presented a higher density of pores with a smaller pore diameter (280 ± 20 nm) compared to PU films (647 ± 54 nm). A 24 h dissolution study showed a gradual release of ITSC from the PMMA film, in a pH dependent manner, reaching almost completion, while PU showed no detectable release. Overall, PMMA films blended with ITSCs present favourable characteristics for biomedical coating applications.