Electrical conductivity of pH-responsive hydrogels.
The electrical conductivity of pH-responsive hydrogels based on cross-linked poly(2-hydroxyethyl methacrylate-co-dimethylaminoethyl methacrylate) copolymers has been studied as a function of pH over the range 5-10, for copolymers containing up to 20 mol% of the amine-containing comonomer. The conductivities of membranes equilibrated in buffered potassium chloride solutions were determined by measuring the electrical resistance of a membrane mounted between the chambers of a modified side-by-side diffusion cell. The conductivity, expressed as a fraction of the conductivity of the buffer in which the gels were equilibrated, ranged from 1% for the gels in the collapsed state to 70% for the most highly swollen gels. The observed results are qualitatively consistent with a proposed model in which the ion concentrations in the fluid phase of the gel are described by Donnan partitioning, and the ion mobilities by the free-volume theory of Yasuda. The results suggest that conductivity measurements may provide an alternative to diffusive transport studies for characterizing moderately swollen hydrogel membranes.
Sheppard
N F
NF
Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.
Lesho
M J
MJ
Tucker
R C
RC
Salehi-Had
S
S
D003432:Cross-Linking Reagents / Q000737:chemistry; D004058:Diffusion; D004553:Electric Conductivity; D005782:Gels; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000737:chemistry; D008433:Mathematics; D008567:Membranes, Artificial; D008689:Methacrylates / Q000737:chemistry*; D011108:Polymers; D011189:Potassium Chloride / Q000737:chemistry
D003432:Cross-Linking Reagents; D005782:Gels; D007202:Indicators and Reagents; D008567:Membranes, Artificial; D008689:Methacrylates; D011108:Polymers; D011189:Potassium Chloride; C005044:hydroxyethyl methacrylate; C049840:2-(dimethylamino)ethyl methacrylate