Positron annihilation studies on chalcone chromophore doped PVA

Abstract

A novel organic non‐linear optical material 1‐(4‐methylphenyl)‐3‐(4‐ N, N dimethyl amino phenyl)‐2‐propen‐1‐one (MPDMAPP) chalcone chromophore has been synthesized by standard method. Pure and MPDMAPP doped Poly(vinyl alcohol) films are prepared using solution casting method and characterized using UV‐Visible absorption and Positron Annihilation Lifetime Spectroscopy. The optical spectroscopic study shows three absorption bands, 196‐202 nm assigned to localized n →π * transitions, 205‐320 nm to n →π * inter‐band and 385‐428 nm assigned to π →π * transition and arises due to the charge transfer complex. Using observed UV‐Vis spectra, three optical energy gaps, Eg1 (4.96–4.25 eV), Eg2 (3.47–3.32 eV) and Eg3 (2.33–2.24 eV) have been estimated. The observed change in Eg upon doping is understood based on the formation of charge transfer complex arising from the –HC=CH– structure present in the composite and due to the interactions of dopant and OH group of PVA. The PALS results shows that the o‐Ps lifetime decreases continuously as doping concentration increases and I3 initially increases (from 18.82% to 20.95%) from 0 wt% to 0.05 wt% and then decreases gradually up to 16.76% for higher dopant concentrations with decrease in optical band gaps. The variation of positron data with Eg is understood by correlating the probability of Ps formation with the complex. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of TiO2 nano‐filler on the electrical conductivity and free volume parameters of PSAN/TiO2 nanocomposites

“…6b-f, which shows the presence of characteristic peaks corresponding to both PSAN and TiO 2 nano-fillers. In addition to the absorbance bands of PSAN, the absorbance bands corresponding to TiO 2 appear at 1,953, 1,879, 1,811, 1,746, 1,583, 1,157 and 500-1,000 cm 21 [29,[35][36][37]. This confirms the presence of TiO 2 in PSAN polymer matrix and the formation of PSAN/TiO 2 nanocomposites.…”

Positron annihilation and other experimental studies on polycarbonate/MPDMAPP nanocomposite

“…The organic chalcone compound MPDMAPP in its pure form shows second harmonic generation (SHG) conversion efficiency of 0.8 times that of urea . However, upon embedding this compound into polymers like poly(methylmethacrylate) (PMMA), poly(vinyl alcohol) (PVA), the composite films are not showing second harmonic behavior, instead these composite films are showing fluorescent properties upon excitation with UV light. The essential requirement for a molecule to show second harmonic is the presence of electron donating groups on one end and electron withdrawing groups in the other end.…”

“…Here, the energy transfer between identical chromophore molecules is known as quenching mechanism, which facilitates the energy migration . This arises mainly due to the reduction in the available free volumes within the polymer matrix and the mobility of chromosphere molecules may restrict by suppressing the free volumes to prevent nonradiative transitions . Hence, the rotational motion of N(CH 3 ) 2 groups of MPDMAPP are not feasible.…”

“…In recent years, polymer‐based nanocomposite materials have played a very important role in scientific and technological areas; because of their wide spread applications in photonics, biotechnology, and optoelectronics in comparison with other classes of engineering materials . Contemporary advancements in modern science and technology require large number of organic photochromic materials with high quality and good responses for numerous optical device applications . This is mainly due to advantages related to their light weight, good mechanical strength, and excellent optical properties, which make them as multifunctional materials.…”

“…The chalcone derivatives are noticeable materials for their excellent blue light transmittance. Polymers embedded with chalcone derivatives normally show good optical properties, fluorescence polarization, color change, fluorescent complex formation, and photochromism …”