title: Diffusion and concentration of molecular probes in thermoresponsive poly(N-isopropylacrylamide) hydrogels: effect of the volume phase transition.
abstract: Poly(N-isopropylacrylamide), NIPA, thermoresponsive hydrogels with well-defined concentrations of an electroactive probe, 1,1'-ferrocenedimethanol, Fc(MeOH)2, were prepared. The discontinuous reversible volume phase transition of such gels occurs at 32 +/- 1 degrees C and results in a release of approximately 93% of the solution from the polymeric network. Transport of Fc(MeOH)2 in both swollen and collapsed gels was studied using steady-state voltammetry and chronoamperometry at platinum microelectrodes. The diffusion coefficient of Fc(MeOH)2 in collapsed gels was approximately 2 orders of magnitude smaller than that in swollen gels. UV/vis spectroscopic studies showed that for 3.0% NIPA gel, the concentration of Fc(MeOH)2 in the collapsed phase was approximately 6 times higher than that in released solution and 4.5 times higher than in the original swollen gel.
authors.affiliation: Department of Chemistry, Brooklyn College and the Graduate Center, City University of New York, 11210-2889, USA.
authors.forename: Weimin
authors.initials: W
authors.lastname: Zhang
authors.forename: Irina
authors.initials: I
authors.lastname: Gaberman
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Ciszkowska