Poly Ethylene Oxide Oligomers Research Articles

Electron-transfer reaction of polyethylene oxide-modified myoglobin in polyethylene oxide oligomers

Electron transfer from an indium tin oxide (ITO) electrode to myoglobin (Mb) in polyethylene oxide (PEO) oligomer was studied. The native Mb was chemically modified with activated PEO (molar mass of 5000 g) to solubilize in the PEO oligomer. PEO-modified Mb (PEO-Mb) was dissolved without denaturation in PEO 200 (molar mass of 200 g) containing 0.50 M KCl as a supporting electrolyte. The ITO electrode, Pt wire and Ag wire were used as the working electrode, the counter-electrode and the reference electrode respectively. PEO-Mb was reduced in PEO 200 under a nitrogen atmosphere when a negative potential (− 1.0 V/Ag) was applied to the working ITO electrode. There are only two species concerned in the reaction, i.e. oxidized PEO-Mb and reduced PEO-Mb which was confirmed by the presence of some isosbestic points in the visible spectra during the electrolysis. This suggested strongly that PEO-Mb received an electron directly from the electrode. The reduction of PEO-Mb was analyzed as a pseudo-first-order reaction. The reduction rate constant of PEO-Mb depended on both the temperature and the degree of PEO modification. PEO-Mb, containing 10.3 PEO 5000 chains on average, showed the highest reduction rate constant (7.6 × 10 −4 s −1 at 25°C). Reduced PEO-Mb was re-oxidized by applying a positive potential (+ 1.0 V/Ag). The reversible redox reaction of PEO-Mb in PEO 200 was confirmed using potentioabsorptometry by applying − 1.0 V/Ag and + 1.0 V/Ag alternately.

Applications of polymer electrolytes: Electrochromics, sensors and biology

Recent advances in the application of polymer electrolytes are introduced, one of which is the application of single-ionic conductors for electrochromic displays. As the electrochromic reactions of both Prussian Blue and WO 3 require migration of only the cation, poly(alkali metal methacrylate-co-oligo(oxyethylene) methacrylate) was actually effective, and the coloring rate was affected by the ionic conductivity. Larger cations such as K + induced better ECD characteristics because of their higher ionic conductivity. The other is for protein reduction. Hemoglobin (Hb) was modified with polyethylene oxide (PEO) to avoid denaturation in PEO oligomers. PEO-modified Hb (3.0 × 10 −5 mol 1 −1) was dissolved in PEO 200 containing 0.5 M KCl, and visible spectra were recorded under the given potential (< −0.5 V vs. Ag). The first order rate constant for the reduction was 2.1 × 10 −4 s −1.

Electrochemical behaviour of hemin and PEO-hemin in ion-conductive polymer matrices

Both iron(III) protoporphyrin IX (hemin) and polyethylene oxide (PEO)-modified hemin (PEO-hemin) were incorporated into liquid or solid state ion-conductive polymer matrices. Their electrochemical behaviour was examined by cyclic voltammetry. Under nitrogen, PEO-hemin (like hemin) shows two redox processes in PEO oligomer. However, in the PEO solution of hemin, only one electrocatalytic reduction wave of dioxygen was observed at −0.50 V (vs. Ag). PEO-hemin also catalysed the electrochemical reduction of dioxygen in solution, and two waves appeared at −0.50 and −0.65 V (vs. Ag). Hemin cannot be dispersed well in solid polymer electrolytes because of the affinity problem. On the contrary, PEO-hemin can be dispersed into them at the molecular level. Similar redox behaviour of PEO-hemin was detected in solid polymer electrolytes. In the solid state, the redox potential of PEO-hemin is always higher than that in solution.

Vibration spectra and conformation of polyethylene oxide oligomers

Vibration spectra and conformation of polyethylene oxide oligomers