Modification of Microelectrode Surface with Hydrogel Layers and Determination of Pore Size in Layers

Hydrogels are three dimensional networks filled with water. Some of the gels can undergo fast, reversible volume phase transition (VPT) in response to a change in environmental conditions. During the transition the gels transform from one state to another (swollen/ shrunken) by changing content of water in the network. Interestingly, the gels have properties of both: solids and liquids. In the macroscopic scale the structure of the network is responsible for the mechanical energy storage. In the microscopic scale the gels exhibit the properties of water: their density is similar and diffusion processes occur in the network [1]. Pores and channels of nanometer size are employed to separate the analytes by size and to control their transport. The size of the pores could be easily changed in the hydrogel matrix by involving the shrinking and swelling process especially in the gels with continuous volume phase transition. The main aim of this paper was to develop an electrochemical method of obtaining the NIPA- and NIPA- co -AA hydrogel films on the microelectrode surface without previous surface functionalization. Another aim was to determine the size of pores/channels in NIPA- and NIPA- co -%AA gels and to evaluate porosity of the gels. The hydrogel films were anchored to the microelectrode surface via electrochemically induced free radical polymerization (EIFRP) process with utilizing the chronoamperometric method. We found that cyclic voltammetry could be also successfully applied to obtain thin hydrogel layers. The electrochemical studies of the discontinuous volume phase transition and the determination of the channel size were done using the ferrocene molecules modified with polyethylene glycol units (PEG) of various length. Figure 1. Woltamperograms obtained during the electrochemically induced free radical polymerization on platinum microelectrode This work was supported by a grant from the National Science Centre of Poland, Preludium 8, 2014/15/ST5/01980 [1] A. B. Imran, T. Seki, Y. Takeok, Polymer Journal, 2010, 42, 839–851 Figure 1