External stimulus‐responsive interfaces in polymer nanocomposites

Materials that can switch from stiff to soft or from brittle to tough by slightly changing the temperature, pH, electric, or magnetic fields of their environments, can have a pronounced impact on many applications, including sensors, biomedical materials for less invasive surgeries, and packaging materials. In this work, temperature‐sensitive poly(N‐isopropyl acrylamide) grafts and low molar mass polyethylene glycol were incorporated in the interfacial region between clay nanoparticles and a bacteria‐derived polyhydroxybutyrate matrix to determine if the application of an external stimulus, such as small changes in temperature, could increase the toughness of the nanocomposites. The obtained materials were characterized by using thermal analysis, infrared spectroscopy, dynamic light scattering and dynamic mechanical tests. Mechanical properties were also evaluated at different temperatures and showed that small changes in temperature, such as from 25°C to 40°C, led to a pronounced increase in strain at break of the nanocomposites containing the modified interface. The external stimulus associated with the increase in temperature from 25°C to 40°C can reduce the interfacial interactions between clay and polymer matrix and create a highly plasticized polymer layer between the components of the nanocomposite, which favored the sliding of the interface and ultimately led to high values of elongation. POLYM. COMPOS., 37:1342–1349, 2016. © 2014 Society of Plastics Engineers