Electrochemical Study of Swelling Change of Poly(N-isopropyl acrylamide) Gels Using Gel-Modified Ultramicroelectrodes

Thermosensitive poly( N-isopropyl acrylamide) (PNIPAAm) gels were chemically modified onto Pt microelectrodes. The modification has been established by chemically introducing vinyl groups onto the electrode surfaces, followed by synthesis of the gels on the surfaces. The gel- modified electrodes were immersed into aqueous solutions containing [Ru(NH ₃ ) ₆ ]Cl ₃ , and elec trochemical measurements were conducted at various temperatures. Independent determination of the diffusion coefficient and concentration of [Ru(NH ₃ ) ₆ ]Cl ₃ in the gels has been achieved by ex ploiting electrochemical methods. The electrochemical response is sensitive to swelling change of the hydrogels. Considerable condensation and suppression in the diffusivity of [Ru(NH ₃ ) ₆ ]Cl ₃ were found in the shrunken gels.