Control of the Hydrophilic/Hydrophobic Behavior of Biodegradable Natural Polymers by Decorating Surfaces with Nano- and Micro-Components

Packaging materials based on natural polymers are becoming popular because these polymers are derived from renewable resources and can display biodegradability. However, natural polymers are typically highly hydrophilic, and packaging films produced with them can absorb water, leading to dimensional changes and reductions in mechanical properties. In this work, films of thermoplastic starch (TPS) and blends of TPS/low-density polyethylene (LDPE) were prepared, and their surfaces were decorated to alter their hydrophilic characteristics. Micro- (polymer microspheres) and nano-components (polycaprolactone electrospun nanofibers) were deposited on the surface of starch and its blends with LDPE. Nanofibers containing silver sulfadiazine were also used to decorate the starch and its blends to change the topography (evaluated by SEM and atomic force microscopy) and to provide anti-bacterial properties. High values of contact angle (CA) and low values of CA hysteresis were measured for the modified surfaces, including a CA higher than 150 degrees and a hysteresis lower than 10 degrees. Therefore, it was demonstrated that the intrinsically hydrophilic surfaces of biodegradable natural polymers could be altered by creating topographical patterns through decoration with nano-/micro-components to generate hydrophobic and even superhydrophobic features that can be useful in minimizing the water absorption of these materials.