Browsing by Subject "Polyaniline"

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    Controlling the photoconductivity: graphene oxide and polyaniline self assembled intercalation
    (American Institute of Physics Inc., 2015) Vempati S.; Ozcan, S.; Uyar, Tamer
    We report on controlling the optoelectronic properties of self-assembled intercalating compound of graphene oxide (GO) and HCl doped polyaniline (PANI). Optical emission and X-ray diffraction studies revealed a secondary doping phenomenon of PANI with -OH and -COOH groups of GO, which essentially arbitrate the intercalation. A control on the polarity and the magnitude of the photoresponse (PR) is harnessed by manipulating the weight ratios of PANI to GO (viz., 1:1.5 and 1:2.2 are abbreviated as PG1.5 and PG2.2, respectively), where ±PR = 100(RDark - RUV-Vis)/RDark and R corresponds to the resistance of the device in dark or UV-Vis illumination. To be precise, the PR from GO, PANI, PG1.5, and PG2.2 are +34%, -111%, -51%, and +58%, respectively.
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    On the possibility of grafting conducting polymers into insulating ones
    (Elsevier, 1996) Bahçeci, S.; Toppare, L.; Yurtsever, E.
    The possibility of grafting between conducting polymers, like polypyrrole (PPy) and polyaniline (PAn), and insulating polymers, such as polybisphenol A carbonate (PC) and polyamide (PA), is studied via semi-empirical methods using the AM1 parametrization. Several experimental studies on the issue have previously revealed that a chemical interaction exists between the couples (PAn-PC, PPy-PC and PPy-PA) during the electrochemical synthesis of PAn and PPy in the insulating host matrices. Here we present additional theoretical evidence indicating that such grafting is possible, at least for small oligomers.
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    Spectroscopic investigation of onset and enhancement of electrical conductivity in PVC/PANI composites and blends by γ-ray or UV irradiation
    (American Chemical Society, 1998) Sevil, U. A.; Güven, O.; Süzer, S.
    Electrical conductivity of blends and composites of poly(vinyl chloride) (PVC) with nonconducting polyaniline (PANI) increases when they are subjected to γ-rays or UV radiation. This is attributed to a radiation-induced dehydrochlorination (loss of HCl) of PVC, which in turn oxidizes (dopes) PANI within the PVC matrix causing the increase in electrical conductivity of these films. XPS, UV - vis - NIR and FTIR spectroscopic methods are used to characterize and verify this novel process. After the films are subjected to γ-rays (or UV radiation) the intensities in the XPS spectra of both -N+- and Cl- peaks increase, confirming the increase in charged species within the PVC matrix. Similar observations attributable to radiation-induced electrical conductivity are also observed in both the UV - vis - NIR and FTIR spectra. This radiation-induced conductivity can also be reversed to some extent by further exposing the films to NH3 vapors, where the oxidized centers are partially reduced (undoped). Several UV/NH3/UV cycles can be performed without much loss in conductivity- and/or conductivity-related spectroscopic features. The onset of the photoinduced conductivity both in PVC-only and PVC/PANI composite films is determined to be 300 nm (4.1 eV), which coincides with the first UV absorption band of PVC.
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    Spectroscopic investigation of polyvinyl chloride photodegradation in blends with basic traps
    (1999) Birer, Özgür
    Polyvinyl chloride degrades via loss of HCI when it is exposed to heat, energetic particles or photons. The mechanism is known as the zip mechanism and results in conjugated segments, polyenes. Degradation also leads to loss of mechanical properties of PVC. However, from another point of view, PVC is a Bronsted acid source, with controllable emission. Furthermore, the polyenes are small segments of polyacetylene, which itself is a very interesting one-dimensional system. Understanding the building blocks clearly helps to envisage larger systems. This study has two main goals. The first goal is benefiting from the radiation induced in-situ created HCI by incorporating basic traps into the polymer matrix and inducing optical or electrical conductivity changes. The second goal is to tune the wavelength of photodegradation by introducing sensitisers into the polymer matrix to affect the chain length of the polyenes. For the first part of the study, pH indicators, and basic forms of conducting polymers were blended with PVC and the films were irradiated with UV radiation. Optical changes were monitored with UV-Vis-NIR Spectroscopy. Similar to several other dyes tried, Bromcresol Green, and Methyl Violet changed their optical properties when they were exposed to UV radiation in the PVC matrix. However, Methyl Violet, being resistant to UV radiation, proved to be a suitable component for possible dosimetric and lithographic applications. Basic forms of polyaniline and poly-2-chloro aniline were blended with PVC, and upon irradiation of the blend, they were converted to conducting salt forms as a result of doping with in-situ created HCI. The structural changes were monitored with UV-Vis-NIR spectrophotometry as well as FTIR spectroscopy. PVC/2-CI PAN I blends gave better results compared to PVC/PANI blends. For the second part of the study, hydroquinone, anthraquinone, and anthracene were introduced into the PVC matrix. The samples were irradiated with monochromatic UV radiation at the absorption maxima of these sensitisers. It was established that the nature of polyene formation is dependent on the wavelength of irradiation as well as the amount of energy transferred to the PVC chains.
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    UV-Vis, IR, and XPS analysis of UV induced changes in PVC composites
    (Elsevier, 1999-05-25) Birer, O.; Süzer, Şefik; Sevil, U. A.; Guven, O.
    PVC undergoes a high degree of dehydrochlorination when exposed to energetic photons. The released HCl (acid), however, can be trapped if a suitable trapping material (base) is also enclosed within the solid matrix as a result of formation an acid-base adduct. Color changes or electrical conductivity changes can easily be obtained if suitable acid-base indicators or conducting polymers in their basic (nonconducting) form are enclosed in the matrix as trapping materials. We used bromcresol green and polyaniline for inducing color and electrical conductivity changes, respectively, within the PVC matrix as a result of exposure to UV light at 254 nm. Both changes can to some extent be reversed by further exposure of the films to NH3 vapour. The color and electrical conductivity changes and their reversibility were followed by using UV–Vis, IR and XPS spectroscopic techniques. q