Xiaoteng Jia

Fabrication of electrochemically responsive surface relief diffraction gratings based on a multifunctional polyamide containing oligoaniline and azo groups

A novel, well-defined multifunctional polyamide bearing pendent aniline tetramer groups has been synthesized via low temperature solution polycondensation. The simultaneous presence of these two functional groups allows the polyamide to display the properties of azo-chromophore and oligoaniline, such as photoinduced birefringence and reversible electroactivity. The electrochromic performance of the polyamide shows the optical change in absorptivity depends on the various redox states of oligoaniline upon electrochemical switching. It is well known that a change in absorptivity is accompanied by a concomitant change in refractive index. By taking advantage of this effect and using the single step fabrication of surface relief gratings based on azo-chromophore, we have fabricated optical diffraction gratings with which the diffraction efficiency can be modulated by an electrochemical signal. Although patterned electroactive films have been made by many techniques, the copolymer approach employing the simple one-step surface relief gratings process displays optimal properties with respect to modulation depth and convenience, which avoids complicated electropolymerization steps or photochemical reactions. The electrochemically-induced modulation in the diffraction efficiency of the polyamide is believed to arise primarily from the effect of the redox state on the films refractive index.

Fabrication of electroactive oligoaniline functionalized poly(amic acid) nanofibers for application as an ammonia sensor

A novel, well-defined, multifunctional electroactive poly(amic acid) (EPAA) containing oligoaniline pendants was synthesized by a one-step synthetic route. The structure was confirmed spectroscopically via nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectra, and the thermal stability was probed via thermogravimetric analysis (TGA). The oligoaniline pendants imparted excellent electroactivity, photoresponsiveness to chemical redox and electrochemical modulation, and expectable electrochromic performance to the obtained EPAA. Leucoemeraldine base EPAA (LEPAA), emeraldine base EPAA (EEPAA) and HCl-doped emeraldine base EPAA (HCl-doped EEPAA) nanofibers were fabricated by electrospinning and were characterized by scanning electron microscopy (SEM) to test their morphology, and a contact angle goniometer was used to test their hydrophilicity. The as-prepared HCl-doped EEPAA nanofibers were then evaluated for their ability to sense ammonia.

Electroactive polymer with oligoanilines in the main chain and azo chromophores in the side chain: synthesis, characterization and dielectric properties

By an oxidative coupling polymerization approach, we have synthesized a novel electroactive polymer with good solubility containing alternating phenyl-capped aniline tetramer in the main chain and azo chromophores in the side chain. Dielectric properties of the as-synthesized polymer were investigated in detail and gratifying results have been observed. Firstly, a large enhancement in the dielectric constant was achieved utilizing the method of doping the conjugated oligoaniline segments with hydrochloric acid. Secondly, the adjustment of dielectric constant was implemented primarily by means of exposing the samples to UV and visible irradiation, mainly owing to the photoisomerization derived from azo chromophores in the side chain. The detailed characteristics of the as-synthesized polymer were systematically studied by Fourier-transform infrared (FTIR) spectra, nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). UV-vis spectra were used to monitor the photoisomerization and doping process of the polymer. The thermal characteristics of the polyamide were evaluated by thermogravimetric analysis (TGA). Moreover, the electrochemical activity of the polymer was explored by cyclic voltammogram (CV) measurement, showing that the intrinsic electroactivity of the oligoaniline was maintained in the polymer.

An efficient fluorescent sensor for redox active species based on novel poly(aryl ether) containing electroactive pendant

We describe the synthesis of a novel poly(aryl ether), containing pendant oligoaniline and anthracene moieties (PAE-p-OA), and both side chains present in equal amounts. Structures were confirmed spectroscopically via nuclear magnetic resonance (NMR), morphological data ascertained viaX-ray diffraction (XRD), and thermal stability probed viathermogravimetric analysis (TGA). Electrochemical and photophysical properties were also investigated using cyclic voltammetry and UV-Vis and fluorescence spectroscopy. This material exhibits an interesting fluorescent response to redox active species. When PAE-p-OA is in the reduced state, oxidative materials interact with the oligoaniline side chains resulting in a progression from leucoemeraldine base (LEB) to the emeraldine base (EB). The resulting change in molecular conformation of the oliganiline unit increases its propensity for interaction with the anthracene side chain (corroborated by molecular modeling), leading to decreased fluorescence via quenching and thus “turn off” fluorescence sensing. When PAE-p-OA is in the oxidized state, reduction of the oligoaniline from the EB to the LEB via interaction with a reductive species delivers “turn on” fluorescence sensing via decreased interaction between the oligoaniline and anthracene side chains, again due to a change in the molecular conformation of oligoaniline.

Synthesis and properties of novel electroactive poly(aryl ether ketone) bearing oligoaniline segments

A novel hyperbranched electroactive azo copolymer with different oligoaniline segments was synthesized by an oxidative coupling polymerization approach, exhibiting an exciting molecular structure. The detailed characteristics of the obtained copolymer were systematically studied by Fourier-transform infrared (FTIR) spectra, nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC) and X-ray powder diffraction (XRD). The thermal resistance of the copolymer was investigated by thermogravimetric analysis (TGA). Through cyclic voltammogram (CV), we explored the electrochemical behavior of the copolymer. Moreover, photoisomerization process and doping process of the copolymer were monitored with UV–vis spectra. Dielectric properties of the as-synthesized copolymer were investigated in detail, and gratifying results have been reported. Firstly, a large enhancement in the dielectric constant was achieved utilizing HCl-doping of the conjugated oligoaniline segments. Secondly, the copolymer in HCl-doped form possessed much higher dielectric constants compared with the similar linear polymer, mainly due to the branched molecular architecture.

Novel electroactive aromatic polyamide with oligoanilines and azo groups in the backbone: synthesis, characterization and dielectric properties

A novel electroactive polyamide with alternating amino-capped aniline pentamer and azo groups in the main chain was synthesized via a four-step synthetic procedure. The characteristics of the obtained polyamide were studied in detail by Fourier-transform infrared (FTIR) spectra, nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). The thermogravimetric analysis (TGA) was used to evaluate its thermal characteristics, and the result showed the as-synthesized polymer had a good thermal stability. Besides, the electrochemical behavior of the polyamide was checked by cyclic voltammetry (CV) and the mechanism of electrochemical oxidation process was well studied. Furthermore, UV–vis spectra were used to monitor the doping process and photoisomerization process of the polyamide. Ratifying results were obtained in the investigation on dielectric properties of the as-synthesized polymer. The dielectric constant was greatly increased by treating the conjugated oligoaniline segments with hydrochloric acid.