PROTONATION THERMODYNAMICS OF MEMBRANES GRAFTED WITH POLYELECTROLYTES CONTROLLING SOLUTE PERMEABILITY

The protonation of two polyelectrolytes with carboxyl groups, grafted on porous cellulose and polyurethane supports, was evaluated by potentiometry, titration calorimetry and Fourier transform IR (FT-IR) spectroscopy in aqueous media. The large potentiometric hysteresis loops observed were indicative of interactions between functional groups of the graft chains and the substrate. This was confirmed by FT-IR spectroscopic and calorimetric analysis. The thermodynamic properties are reviewed in relation to applications concerning solute permeability. The pH-sensitive porous membrane, having a ''chemical valve'' function, self-regulated insulin release in response to the pH of the surrounding solution. The porosity of the membrane was controlled by the charge state conformations of grafted polyacids.