Unnikrishnan Gopalakrishnapanicker

Effect of cellulose whisker content on the properties of poly(ethylene-co-vinyl acetate)/cellulose composites.

The reinforcing effect of cellulose whiskers, produced from banana waste fibres, has been investigated using poly(ethylene-co-vinyl acetate) [EVA]/cellulose whisker composites. Cellulose whiskers, approximately 300 nm long and 30 nm wide, were obtained via a sulphuric acid hydrolysis method. The effects of the cellulose whisker loading on the thermal properties, mechanical properties and on the morphological features of the composites have been investigated. EVA copolymer with a vinyl acetate segment content of 40% has been used for composite fabrication. The developed composites showed superior thermal and mechanical properties relative to that of the EVA copolymer alone. Three theoretical models, namely the Halpin-Tsai model, the Kerner model and the Nicolais-Narkis model have been employed to provide a basis for the comparison of the results with the observations from the tensile investigations.

Deproteinised natural rubber latex grafted poly(dimethylaminoethyl methacrylate) – poly(vinyl alcohol) blend membranes: Synthesis, properties and application

Natural rubber latex was initially deproteinised (DNRL) and then subjected to physicochemical modifications to make high functional membranes for drug delivery applications. Initially, DNRL was prepared by incubating with urea, sodiumdodecylsulphate and acetone followed by centrifugation. The deproteinisation was confirmed by CHN analysis. The DNRL was then chemically modified by grafting (dimethylaminoethyl methacrylate) onto NR particles by using a redox initiator system viz; cumene hydroperoxide/tetraethylenepentamine, followed by dialysis for purification. The grafting was confirmed by dynamic light scattering, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The grafted system was blended with a hydrophilic adhesive polymer PVA and casted into membranes. The membranes after blending showed enhanced mechanical properties with a threshold concentration of PVA. The moisture uptake, swelling and water contact angle experiments indicated an increased hydrophilicity with an increased PVA content in the blend membranes. The grafted DNRL possessed significant antibacterial property which has been found to be retained in the blended form. A notable decrease in cytotoxicity was observed for the modified DNRL membranes than the bare DNRL membranes. The in-vitro drug release studies using rhodamine B as a model drug, confirmed the utility of the prepared membranes to function as a drug delivery matrix.

Characterization of Europium Complex-doped PMMA and PMMA-EVA Polymer Networks

Europium-β-diketone chelate doped poly(methyl methacrylate) and poly(methyl methacrylate)/poly(ethylene co-vinyl acetate) blends have been successfully prepared and characterized. The mechanical properties of the PMMA-EVA systems have been assessed in terms of tensile strength and impact strength. The thermal characteristics and the energy involved in thermal decomposition have been studied. The structural properties of the complex doped polymeric systems reveal that the complex exists in the same crystalline state in the doped systems as it does in the pure state. The orientations of the groups in the host matrix have been found to be affected by the complex loading. The optical properties of the system have been studied by photo luminescence spectroscopy. The fluorescence lifetime have been observed to decrease at greater loadings of the complex; an effect that has been attributed to concentration quenching. The complex doped PMMA/EVA polymer network developed is considered to be a potential candidate for the development of optoelectronic devices those possess superior mechanical properties.

Transport Properties Through Polymer Membranes

The transport features of liquids, gases, and vapors through polymeric membranes play a crucial role in many applications including membrane separation processes, food packaging, and protective coatings. A thorough understanding of the basic theories, mechanisms, and the influencing factors of transport phenomena through polymeric membranes is crucial in all these applications. This chapter focuses on the fundamental aspects and applications of transport properties of polymer membranes.

Optoelectrical, morphological and mechanical features of nitrophenyl supported poly(1,3,4-oxadiazole)s and their nanocomposites with TiO2

Two nitro phenyl supported poly(1,3,4-oxadiazole)s viz.; poly(pyridine(2-nitrophenyl)-1,3,4-oxadiazole) [PPNO] and poly(2-(o-nitrophenyl)-5-phenyl-1,3,4-oxadiazole) [PNPPO] were initially synthesized by a dehydrocyclization reaction, and then reinforced with TiO2 nanoparticles. They were characterized in terms of optoelectrical, morphological and mechanical properties in order to examine their suitability to function as active or electron transport layers in polymer light emitting diodes (PLEDs). The nanocomposites have been found to possess charge transfer characteristics from the macromolecular systems (PPNO or PNPPO) to TiO2 particles, upon photo-excitation. Cyclic voltammetric examinations indicated a reduction in band gap for PPNO and PNPPO in the presence of TiO2 nanoparticles. The nonlinear optical responses and optical limiting behavior of PPNO, PNPPO and their nanocomposites were also evaluated by the Z-scan technique, using nanosecond Nd:YAG, 532 nm laser radiations. In view of user-friendly device fabrication, flexible films of PPNO and PNPPO were fabricated by blending the composites with 2 wt% of poly(methylmethacrylate). Along with good mechanical properties, PPNO and PNPPO showed high fluorescent quantum yield, presenting them as promising candidates for PLED fabrication. Interestingly, the current–voltage (I–V) characteristics propose their additional application as semiconducting packaging materials for optoelectronic devices.