Porous exfoliated poly(ε-caprolactone)/clay nanocomposites: Preparation, structure, and properties

Porous biodegradable poly(ε-caprolactone) (PCL)/clay nanocomposites were prepared by incorporating a blowing agent into the galleries of an organoclay, followed by mixing the pretreated organoclay and PCL to give partially intercalated and exfoliated nanocomposites and subsequently degrading the blowing agent in situ to increase the exfoliation degree in the porous nanocomposites. The blowing agent played dual roles in the foaming process: formation of bubbles and facilitation of clay exfoliation, which were confirmed by X-ray diffraction and transmission electron microscopy. Such porous nanocomposites possessed significantly more uniform porous structures and smaller pore sizes compared to their polymer counterparts, which were characterized by X-ray micro computed tomography. They also exhibited increases of the thermal degradation temperature by 41°C, the compressive modulus by 152%, and the compressive stress at 10% strain by 177%. The relative modulus-relative density relationship of the porous nanocomposites was found to follow the Mills-Zhu model for closed cells. Such porous biocompatible and biodegradable nanocomposites will find potential applications in, for example, carriers of chemicals, drugs, and medical and diagnostic devices.