Athianna Muthusamy

Synthesis, characterization, optical and electrical properties of thermally stable polyazomethines derived from 4,4′-oxydianiline

Three soluble, thermally stable azomethine polymers were synthesized by the oxidative polycondensation of azomethine bisphenols using NaOCl as an oxidant in aqueous alkaline medium. The azomethine bisphenol monomers, 4,4′-oxybis[N-(2-hydroxy-3-methoxybenzilidine)aniline], 4,4′-oxybis[N-(2-hydroxy-5-bromobenzilidine)aniline] and 4,4′-oxybis[N-(2-hydroxynaphthalidine) aniline] were synthesized by the condensation of 4,4′-oxydianiline with three aromatic aldehydes. The structures of the monomers and polymers were confirmed by Fourier Transform infrared spectroscopy, UV–visible, 1H-NMR and 13C-NMR spectroscopic techniques. Morphology of the synthesized polymers was characterized using scanning electron microscope. The thermal stability of the polymers is evidenced by high carbines residue obtained in TGA. Fluorescence spectra showed that the emission maxima centred in the region 420–460 nm for all the compounds with large stokes shift values (∆λST). Electrical conductivity of iodine-doped polymers was measured by four-point probe technique. The synthesized polymers have shown good electrical conductivity on iodine doping, and it increases with the increase in iodine vapour contact time. The self-extinguishing property of the synthesized polymers was studied by the calculation of the limiting oxygen index values with van Krevelen’s equation.

Synthesis and Spectral Characterization of Cross Linked Rigid Structured Schiff Base Polymers: Effect of Substituent Position Changes on Optical, Electrical, and Thermal Properties

ABSTRACT Three Schiff base diol monomers were oxidatively polymerized with NaOCl as an oxidant. The structures of the monomers and polymers were confirmed by various spectroscopic techniques. Conductivity of the iodine doped polymers measured was compared based on the total charges on imine nitrogen calculated by Huckel method. The polymers were having quite lower band gap than the monomers. Fluorescence spectra of monomers and polymers showed that the excitation and emission maxima centered in the region 362–400 nm and 467–513 nm with large stokes shift. High carbine residue, around 50% at 800°C confirmed that the polymers were having good thermal stability. GRAPHICAL ABSTRACT

Investigation of aggregation induced emission in 4-hydroxy-3-methoxybenzaldehyde azine and polyazine towards application in (opto) electronics: synthesis, characterization, photophysical and electrical properties

Abstract An azine monomer 4-hydroxy-3-methoxybenzaldehyde azine was synthesized by refluxing with ethanolic solution of vanillin with hydrazine hydrate. It was then converted into polyazine by oxidative polymerization. The structure of azine and polyazine was characterized by FT-IR, UV–visible, 1H-NMR and 13C-NMR. Spectral results suggest the formation of polymer, through C–C and C–O–C coupling of the phenylene and oxyphenylene. The relationship between the structures and photophysical properties of azine and polyazine was studied. Both azine and polyazine show, aggregation induced emission with increase in concentration in DMSO solution. The single crystal structure of azine suggesting the various inter and intra molecular interactions rigidify the conformation and locked the intramolecular rotations of the phenyl rings in the molecule. The inhibition of intramolecular rotation, J- aggregation and increase of conjugation impart the fluorescence in aggregated state. Additionally, the electronic properties namely orbital energies and resulting energy gap calculated theoretically by density functional theory (DFT).

Studies on Photoreactive Polyesters Containing α, β-Unsaturated Carbonyl Group in the Main Chain

A series of polyesters containing °-unsaturated carbonyl group in the main chain was synthesized from 1,3-bis(4-hydroxyphenyl)propenone and 3-(4-hydroxy-3-methoxyphenyl)-1-(4-hydroxyphenyl)propenone with various aliphatic and aromatic acid chlorides by an interfacial polycondensation method using a phase transfer catalyst. The structure of the synthesized monomers and polyesters was confirmed by IR, 1H NMR, 13C NMR and UV spectroscopy. These polyesters were studied for their thermal and photochemical properties. The thermal properties of polyesters were evaluated by thermogravimetric analysis and differential scanning calorimetry. The polyesters synthesized from aromatic acid chlorides have shown higher thermal stability than the polyesters from aliphatic acid chlorides. Moreover, the results revealed that the polyesters bearing methoxy substituent on the phenyl ring group possess lower thermal stability than non-substituted polyesters. The photoreactive property of the polyesters was studied by UV and IR spectrophotometer. It is observed that on exposure to UV light the polymers undergo photocrosslinking reaction. The photocrosslinking proceeds through the dimerization of olefinic chromophore via 2 + 2 cycloaddition reaction.

Synthesis, characterization, optical, thermal and electrical properties of polybenzimidazoles

ABSTRACT The variation of dielectric constant and dielectric loss of two novel polybenzimidazole (PBI) were studied at constant temperature with variable frequency. The polymers have shown maximum dielectric constant at low applied frequency 50 Hz at 393 K due to the space charge polarization. The AC conductivity and activation energy of polymers were arrived from dielectric constant and dielectric loss values. PBIs were synthesized by the oxidative polycondensation of benzimidazole monomers, 2-(1H-benzo [d] imidazole-2-yl)-4-bromophenol (BIBP), and 2-(1H-benzo [d] imidazole-2-yl)-6-methoxyphenol (BIMP) in an aqueous alkaline medium using NaOCl as oxidant. The monomers and polymers were characterized by various spectroscopic techniques. Fluorescence spectra of monomers and polymers showed their λ max emission in the region of 472–479 and 463–472 nm respectively. The electrical conductivities of iodine doped polybenzimidazoles were measured by four-point probe technique and it increases with increase in iodine vapour contact time. The electrical conductivity values were correlated with the charge density on imidazole nitrogen obtained from Huckel calculation method. Both the PBI are having reasonably good thermal stability and are shown by high carbines residues of around 40% at 500°C in thermogravimetric analysis.

Electrical and magnetic properties of poly( m -phenylenediamine)/NiFe 2 O 4 nanocomposites

Poly(m-phenylenediamine) (PmPD)/NiFe2O4 nanocomposites were synthesized by in situ oxidative polymerization containing two different ratios of NiFe2O4 nanoparticles (10 and 20%). Dielectric studies of PmPD/NiFe2O4 nanocomposites were carried out at different temperature and frequency. Dielectric constants of PmPD/NiFe2O4 nanocomposites vary with the concentration of NiFe2O4 nanoparticles. Magnetic measurements of NiFe2O4 nanoparticles and PmPD/NiFe2O4 nanocomposites showed that they have ferromagnetic behaviour at room temperature. The XRD patterns of PmPD/NiFe2O4 nanocomposites are confirming the incorporation of NiFe2O4 nanoparticles into PmPD polymer. Room temperature Mössbauer spectrum of NiFe2O4 nanoparticles demonstrated that the Fe is in 3+ oxidation state with cubic structure. The SEM image of PmPD shows sphere like morphology. TGA suggest that thermal stability of PmPD/NiFe2O4 nanocomposites is greater than PmPD.