Characterization of dimethyldiallylammonium chloride and other polyelectrolytes in bulk films and on electrode surfaces

Dimethyldiallylammonium chloride (DMDAAC) is a cationic polyelectrolyte which has been immobilized by gamma irradiation onto electrode surfaces. Fundamental to the immobilization procedure is the presence (originally fortuitously) of monomer in the polymer to be immobilized. It is the polymerization of this monomer which leads to network formation and therefore immobilization at the electrode surface. No immobilization is observed in the absence of this monomer. The immobilized network exhibits typical ion-exchange properties such as the ability to preconcentrate anionic species as well as being influenced by the nature of the anions in the supporting electrolyte.; Varying the percentage of monomer prior to irradiation has lead to the development of polyDMDAAC modified-electrodes which exhibit varying response to solution species. This was exemplified in experiments where specificity in response is observed between vitamin B-12 and benzoquinone based on size exclusion properties.; The polymerization of monomer was studied in bulk films by NMR and found to occur at as low as 60 Krad. Based on this information polyDMDAAC was immobilized at electrodes at dosages as low as 500 Krad. Ferricyanide can be charge-trapped in the immobilized polymer and used to detect H{dollar}sb2{dollar}O{dollar}sb2{dollar} in a detection scheme based on the chemical oxidation (by H{dollar}sb2{dollar}O{dollar}sb2{dollar}) of electrochemically generated ferrocyanide. This results in a signal proportional to the H{dollar}sb2{dollar}O{dollar}sb2{dollar} concentration present.; The successful immobilization of macromolecules was studied with a polyDMDAAC/poly N-vinyl pyrrolidone/N-vinyl pyrrolidone system. This study is intended to mimic the immobilization of an enzyme or antibody for future sensor development.; The immobilization procedure using gamma irradiation has been extended to microelectrodes with the fabrication of modified microelectrodes. Carbon-fiber microelectrodes (diameter ca. 10 uM by scanning electron microscopy) modified with polyDMDAAC and irradiated exhibit charge-trapping of ferricyanide from solution.