Biomimetic chitosan-treated clay–elastomer composites with water-responsive mechanically dynamic properties



Biomimetic hydrophobic polymer composites with water-responsive mechanically adaptive behaviors were successfully prepared using hydrophilic chitosan-treated clay (chi-clay) as the water-activated, pH-sensitive and reinforcing phase and elastomeric thermoplastic polyurethane (TPU) as the matrix. Structural characterization, swelling tests in three representative solutions with different pH values, and dynamic mechanical analysis under wet and dry conditions were performed on the resultant chi-clay-TPU composites with varying chi-clay contents. The results showed that the equilibrium swelling degree of TPU increased significantly with increasing chi-clay content and that water transportation in all the composites followed Fickian diffusion mechanism. The presence of chi-clay provided remarkable enhancement of the storage modulus of TPU and offered water-responsive changes of the modulus. Such changes increased with chi-clay content and were pH-sensitive, with the acidic condition rendering the largest modulus difference. These water-responsive polymer composites may find potential applications in biomedical fields and beyond. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 55–62