Switchable and pH responsive porous surfaces based on polypeptide-based block copolymers

In the current work, we prepared stimuli responsive porous films by the breath figure approach using polymer blends consisting of high molecular weight polystyrene (HPS) and an amphiphilic block copolymer based on a pH sensitive poly(L-glutamic acid) (PGA) polypeptide. Thus, due to the breath figure mechanism the pores were enriched in pH responsive negatively charged carboxylate groups able to immobilize cationic molecules at pH above the pKa of the PGA. As a proof of concept, Rhodamine 6G was attached through electrostatic interactions at basic pH inside the cavities as shown by fluorescence microscopy. The variation of the wettability and the reversible immobilization of Rhodamine 6G as a function of pH were investigated by contact angle and fluorescence measurements. Moreover, the kinetics of the adsorption process of Rhodamine 6G onto the prepared smart films was explored evidencing a pseudo-second order kinetic model while the maximum absorption capacity at equilibrium was found to be similar to 6.4 nmol g(-1).