Ferrocene redox polymers based on the coupling of ferrocenecarboxyaldehyde to both linear and branched poly(ethylenimine) [PEI] have been prepared to investigate the effects of pH, electrolyte, and crosslinking on electron charge transport and film swelling. The redox behavior of both the ferrocene-modified linear poly(ethylenimine) (Fc-LPEI) and the ferrocene-modified branched poly(ethylenimine) (Fc-BPEI) was investigated by cyclic voltammetry (CV), while the first electron diffusion coefficients reported for PEI based redox polymers were determined by electrochemical impedance spectroscopy. Novel and previously unreported multiple redox wave behavior was observed for these materials under certain conditions. In phosphate solutions at pH > 7, crosslinked films of both redox polymers exhibited multiple redox wave behavior and were unstable. In contrast in non-phosphate solutions crosslinked films exhibited stable electrochemical behavior and fast electron transfer in solutions with pH < 11. Gel swelling experiments suggested that the multiple wave behavior and instability exhibited in either phosphate solutions or at high pH in non-phosphate solutions were related to a combination of film collapse and electrolyte binding within the hydrogel. The electron diffusion coefficients for these polymers are on the order of 10-8 (mol cm-2 s-1/2) which are approximately 40 times greater than similar materials. Incorporation of the enzyme, glucose oxidase, into these films demonstrated that these redox polymers were able to electrically communicate with the enzyme's FAD redox centers. Glucose sensors based on these films exhibited glucose electrooxidation current densities that ranged from 240-480 ?A/cm2 which were dependent upon the supporting electrolyte and pH.