The present work reports an investigation on the modification of conducting polyaniline (PANI) characteristics favorably on blending with the neutral polymer, poly(vinyl pyrrolidone) (PVP) in a systematic variation of their molar ratios (aniline : PVP 5 4 : 1, 2 : 1, 1 : 1, 1 : 2, and 1 : 3). Prepared by precipitation technique by conventional in situ chemical oxidative polymerization with ammonium peroxodisulfate in aqueous H 2 SO 4 medium (pH 1.0), these materials have nanometer sizes ($ 50-200 nm) and, depending on the molar ratios, exhibit a distinct deviation in physicochemical characteristics from those of pristine PANI prepared in the identical condition. A gradual trend in characteristics is noticed in first three PANI-PVP blends, while an abnormal hike in conductivity, unusual spectral features in IR and UV-vis, hardened nature, and induction of characteristic morphology, crystallinity, and thermal stability are associated with the last two blends that have excess PVP. Thus a division of two sets of nanoblends, one set with less or equal content of PVP and another with excess of PVP, emerges. Evidently, PVP has a tuning effect on PANI through its dopant, supporting matrix and interpenetrating steric stabilizer acts in proportion quite unusual to its neutral nature. The study altogether brings to light a simple way of modification of PANI characteristics by conventional method of blend synthesis.
Nimbolide 1, a potent molecule of biological significance, was isolated. Attempts were made to cleave the ether linkage in nimbolide using boron trifluoride etherate in the presence of tetrabutyl ammonium bromide so as to generate a ring-opened structure akin to azadirachtins, which are known to possess excellent antifeedant properties. However, a novel rearranged product was envisaged during the course of the reaction, which was determined as isonimbolide 2-a structural isomer of nimbolide through spectroscopic methods.
An investigation on the effect of β β-cyclodextrin (CD) in both free and inclusion-complexed forms with a guest anionic metal complex, dioxalatodiaquochromate(III) (DDC), on the characteristics of conducting polyaniline (PANI) is carried out. Four materials, PANI (i.e. PANI-SO 4 2-), PANI-DDC, PANI-CD and PANI-CD + DDC were prepared by in situ chemical oxidative polymerization in aqueous H 2 SO 4 at pH 1 and subjected to electrical conductivity and spectral (IR and UV-vis) measurements. DDC and CD when separately incorporated, reduce the conductivity of PANI by about half whilst their inclusion complex CD + DDC enhances it. Spectral characterization reveals that DDC as a dopant and CD as an encapsule exhibit their effects through adverse interaction with imine-amine N centres and benzenoid moiety of PANI. The inclusion complex CD + DDC, on the contrary, functions as a dopant by lying in between the chains and seems to promote the extended conformation of PANI chain and hence the π π-electron delocalization. Exposure of the material to methanol vapour causes a decrease in conductivity in PANI and PANI-CD while an increase in PANI-CD + DDC. This study makes explicit the distinct role of CD as an encapsule and CD + DDC inclusion complex as a dopant in altering the electrical property of PANI.
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