Size-sensitive Kinetics of Ion Exchange for Macro-, Micro-, and Nanogels

Keywords:
pH-responsive hydrogel, nanogels, ionic reservoir, time-resolved pH measurements

Abstract:
Ion-sensitive polymer network (hydrogel) can function as an ionic reservoir accumulating and releasing ions. Our hypothesis is that characteristic rates of ion exchange kinetics has to be size-dependent. This could be promising for characterization of nanometer sized hydrogel particles. We measured the changes in ion concentrations in the exterior to the particles with time. This kinetic approach is also an analytical tool to study the mechanical and electrochemical behavior of pH-responsive hydrogel submicron particles. The time-resolved measurements of pH equilibration in external suspension of macro-, micro-, and nanogels was studied. Chemical kinetics was applied to estimate the rates of ion diffusion and binding within hydrogel particles of different sizes in order to show that parameters of protonation/deprotonation kinetics (Figure 1) in polymer network are size-dependent. The kinetics of ion exchange in the artificial polymer hydrogels can be used for monitoring the formation of hydrogel nanostructures, characterizing their properties, controlling the operation of nanodevices, and for modelling biological functions of the living cell.

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Nanotech 2006 Conference Program Abstract