Hsiu-Ying Huang

Electrochemical investigations on anticorrosive and electrochromic properties of electroactive polyurea

In this study, electrochemical investigation of corrosion protection and electrochromic properties of aniline-pentamer-based electroactive polyurea (EPU) coating prepared by oxidative coupling polymerization is presented. Monitoring of the in situ chemical oxidation process for the reduced form of soluble EPU in N-methyl-2-pyrrolidone (NMP) by the incorporation of an oxidant was performed by measuring UV-Visible absorption spectra. Moreover, the electroactivity of EPU was evaluated by performing electrochemical cyclic voltammetry (CV) studies. The EPU coating was found to exhibit enhanced corrosion protection effect on cold-rolled steel (CRS) electrodes as compared to a corresponding non-electroactive polyurea (NEPU) coating based on a series of electrochemical measurements in 3.5 wt% NaCl electrolyte. The electrochromic performance of EPU was investigated by measuring electrochromic photographs and UV absorption spectra.

The use of a carbon paste electrode mixed with multiwalled carbon nanotube/electroactive polyimide composites as an electrode for sensing ascorbic acid

Carbon paste electrodes (CPEs) modified by the addition of amino-functionalized multiwalled carbon nanotube/electroactive polyimide (AF–MWCNT/EPI) composites (AF–MWCNT/EPI-CPE) have been prepared and applied to the electrochemical sensing of ascorbic acid (AA). First, MWCNTs were grafted with 4-aminobenzoic acid in a medium of polyphosphoric acid/phosphorus pentoxide to obtain MWCNTs functionalized with 4-aminobenzoyl groups (AF–MWCNTs). The amino functional groups on the AF–MWCNTs reacted with an oligoaniline by oxidative coupling polymerization to yield the AF–MWCNT/EPI composites. Fourier transform infrared spectra and Ultraviolet-Visible absorption spectra revealed that the quinoid rings present on the EPI graft interacted with the AF–MWCNTs. Cyclic voltammetry studies indicated improved electrochemical properties of the AF–MWCNT/EPI composites, demonstrating the occurrence of efficient electron/charge transfer between the AF–MWCNTs and the EPI graft. The concentration of the added AA and the change in the peak current obtained showed a linear relationship. In addition, the calibration curve of the amperometric response of the AF–MWCNT/EPI-CPE sensors against the concentration of AA was also linear. The detection limit and the sensitivity of the AF–MWCNT/EPI-CPE AA sensors were 4.1 μM at a S/N (signal to noise ratio) of 3 and 27.5 μA mM−1, respectively.

Photoactively electroactive polyamide with azo group in the main chain via oxidative coupling polymerization

In this work, a simultaneously photoactive and electroactive polyamide exhibiting interesting spectroscopic and electrochemical properties was prepared. Firstly, a 4-aminoazobenzene-capped amide oligomer (ACAO) was synthesized and characterized by 1H NMR, 13C NMR and mass spectroscopy. Subsequently, the photoactively electroactive polyamide was synthesized through reacting ACAO with p-phenylenediamine by oxidative coupling polymerization, followed by characterization with GPC and 1H NMR. After alternate irradiation with UV and visible light, the azobenzene exhibited obvious photoelectrochemical switching properties. The reversible photoisomerization (i.e., cis ↔ trans) behaviour of the backbone azobenzene moieties in the as-prepared photoactively electroactive polyamide was analyzed by in situ monitoring through systematic studies of UV-visible and 1H NMR spectroscopies. On the other hand, the electrochemical activity (i.e., redox capability) of the as-prepared polyamide was explored by cyclic voltammetry (CV) measurements.

Structural and electrical characterization of polyanilines synthesized from chemical oxidative polymerization via doping/de-doping/re-doping processes

Structural characterization of various emeraldine salt (ES) and emeraldine base (EB) polyaniline (PANI) powders synthesized from chemical oxidative polymerization and then via de-doping and re-doping processes is first presented. Partial crystallinity with well-separated x-ray diffraction peaks is observed in the as-prepared ES PANI powder and an amorphous characteristic is identified in the de-doped EB PANI powder. From scanning electron microscopy, both the nanostructures of the as-prepared ES and de-doped EB PANI precipitated powders possess similar morphology. This finding reveals that the de-doping process to remove the counter-ions intercalated between the as-prepared ES PANI chains makes the de-doped EB PANI pieces become soft but does not change the nanostructures significantly. Then, the electrical conductivity perpendicular to the surface of the pressed PANI disc pellets is studied. The re-doped ES PANI pellets possess less electrical conductivity than their as-prepared counterparts, which suggests that during the re-doping process the counter-ions (Cl− or ) are re-adsorbed predominantly on the surface region of the PANI nanostructures. Besides, the re-doping of larger counter-ions (with respect to Cl−) intercalated between the PANI chains increases the d-spacing of (1 0 0) planes and hence reduces the corresponding π–π inter-chain interaction. Finally, from the temperature dependence of the electrical conductivity together with the structural information, the charge carrier hopping mechanisms perpendicular to the surface of the pressed pellets corresponding to various PANI samples are compared and discussed.