Journal of Membrane Science, Vol.497, 328-338, 2016
Diffusional permeability characteristics of positively K+ -responsive membranes caused by spontaneously changing membrane pore size and surface wettability
Diffusional permeability characteristics of K+-responsive membranes with grafted poly(N-isopropylacrylamide-co-acryloylamidobenzo-15-crown-5) (poly(NIPAM-co-AAB(15)C(5))) chains in membrane pores are investigated systematically. Upon specifically recognizing K+, the grafted membrane gates dramatically switch from swollen and hydrophilic state to shrunken and hydrophobic state. The K+-responsive solute diffusion is controlled not only by the K+-triggered isothermal change of membrane pores from "closed" to "open" state but also heavily by the hydrophilic/hydrophobic switching of grafted gates. For K+-responsive diffusional permeability characteristics of the positively K+-responsive membranes, there presents a threshold value of the molecule size, which divides the solutes being promoted or restricted to diffuse across the grafted membrane upon presence of K+ in environment. With size smaller than the threshold value, the solutes are promoted to diffuse across the grafted gating membrane in the K+ solution compared with that in water; when the solute size is larger than the threshold value, the diffusion of solutes across the membrane is resisted in K+ solution. The longer and the denser the grafted chains, the easier the membrane pores being choked with the grafted copolymer chains in the shrunken state. As a result, the larger the grafting yield of poly(NIPAM-co-AAB15C5), the smaller the threshold value of the molecule size. The results in this study are valuable for rationally designing K+-responsive controlled release systems for biomedical purpose. (C) 2015 Elsevier B.V. All rights reserved.
Keywords:Smart gating membranes;Diffusional permeability;Host-guest recognition;Phase transition;Potassium-ion-response