Bilayer coated capsule membranes. Part 2. Photoresponsive permeability control of sodium chloride across a capsule membrane

Abstract

Two types of photoresponsive nylon capsules coated with synthetic bilayer membranes were prepared. In one system, the azobenzene chromophore is incorporated in the bilayer component (System I); the other system contains the azobenzene moiety as part of the polyamide chain (System II). Release of NaCl from nylon capsules coated with photoresponsive bilayer membranes (System I) was reversibly regulated by alternate irradiation with u.v. or visible light. Thus, permeation of NaCl was enhanced due to the distorted cis-configuration of the azobenzene unit in bilayers, and reverted to the original rate by recovery of the trans-configuration. NaCl release was also affected by the phase transition of the coating bilayer membrane. The permeation mechanism is discussed from the activation energy data. Permeation of the System II capsule, in which the azobenzene unit is linked covalently, was not changed by photo-irradiation.