Bio-hybrid foams by silsesquioxanes cross-linked thermoplastic zein films

Hybrid materials, a new class of materials obtained by sol-gel approach and based on the nanoscale interaction between inorganic and organic phases, have recently gained large scientific and industrial attention. In this work, the material designing of zein hybrid materials with tailored properties is addressed to the production of zein hybrid foams by both gas foaming and supercritical carbon dioxide, CO2 drying. Hybrid materials have been produced from thermoplastic zein and 3-glycidoxypropyltrimethoxysilane by a two-step procedure including reactive melt mixing and a simultaneous sol-gel approach. Protein structural changes have been investigated by infrared spectroscopy and correlated with thermomechanical properties. The hybrid foams have been analyzed by scanning electron microscopy in order to evaluate the effect of silsesquioxanes domains on the porous structure. Hybrid microcellular foams with homogeneous cellular structures have been obtained by both foaming approaches. A bimodal structure with bubbles characterized by micrometric and nanometric sizes was obtained in hybrid foams obtained with CO2 drying.