Polyacrylamide hydrogels with trapped sulfonated polyaniline

A new type of semi-interpenetrating network system consisting of a flexible polyacrylamide hydrogel with embedded stiff-chain linear polyelectrolyte, sulfonated polyaniline (SPANI), has been investigated. It is shown experimentally that the incorporation of stiff-chain polyelectrolyte inside the uncharged PAA network brings different swelling behavior from the pure PAA gel. Environmental pH values have remarkable influence to the swelling degree of this new gel system, the maximum swelling degree, appearing at the environmental pH value of about 12, can be 17 times greater than that at pH 1, and 12 times greater than that at pH 14. Release kinetics of SPANI has shown that SPANI is effectively retained by the gels in acidic or neutral environment, although they are not covalently attached to the network chains; but in alkaline environment, the entrapped SPANI molecules will be released into the surrounding solution gradually. The diffusion coefficient of SPANI is calculated from the experimental data. The experimental phenomena are tried to interpreted from aspects of aggregation and hydrogen bonding between SPANI chains.