Sunita Rattan

Swift Heavy Ion Irradiation as a Tool for Homogeneous Dispersion of Nanographite Platelets within the Polymer Matrices: Toward Tailoring the Properties of PEDOT:PSS/Nanographite Nanocomposites

UNLABELLED Performance of the polymer nanocomposites is dependent to a great extent on efficient and homogeneous dispersion of nanoparticles in polymeric matrices. The dispersion of nanographite platelets (NGPs) in polymer matrix is a great challenge because of the inherent inert nature of the NGPs, poor wettability toward polymer matrices, and easy agglomeration due to van der Waals interactions. In the present study, attempts have been made to use a new approach involving the irradiation of polymer nanocomposites through swift heavy ion (SHI) to homogeneously disperse the NGPs within the polymer matrices. Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) ( PEDOT PSS)/nanographite nanocomposite (NC) films prepared by the solution blending method were irradiated with SHI (Ni ion beam, 80 MeV) at a fluence range of 1 × 10(10) to 1 × 10(12) ions/cm(2). XRD studies revealed that ion irradiation results in delamination and better dispersion of NGPs in the irradiated nanocomposite films compared to unirradiated films, which is also depicted through SEM, AFM, TEM, and Raman studies. In the irradiated polymer nanocomposite films, the conformation of PEDOT chains changes from coiled to extended coiled structure, which, along with homogeneously dispersed NGPs in irradiated NCs, shows an excellent synergistic effect facilitating charge transport. The remarkable improvement in conductivity from 1.9 × 10(-2) in unirradiated NCs to 0.45 S/cm in irradiated NCs is observed with marked improvement in sensing the response toward nitroaromatic vapors at room temperature. The temperature induced conductivity studies have been carried out for PEDOT PSS/nanographite NCs to comprehend the charge transport mechanism in NC films using the 3D Mott variable range hopping model also. The study reveals SHI as a novel method, addressing the challenge associated with the dispersion of NGPs within the polymer matrix for their enhanced performance toward various applications.

Polymer nanocomposites using click chemistry: novel materials for hydrogen peroxide vapor sensors

Herein, we report the synthesis of nanocomposites (NCs) prepared by azide-functionalized polystyrene (Az-f-PS) coupled with alkyne-functionalized nanographite platelets (Alk-f-NGPs) by using copper(I) catalyzed azide–alkyne click chemistry. Linear polystyrene (PS) was functionalized with an azide moiety after bromine-termination of PS through atom transfer radical polymerization (ATRP) using CuBr/2,2′-bipyridyl as a catalyst. The nanographite platelets (NGPs) were formed from graphite flakes through intercalation followed by functionalization with an alkyne moiety. The structure and micromorphology of the prepared NCs were confirmed by NMR, FTIR, Raman, XRD, TGA, SEM, TEM and AFM techniques. The electrical properties of the click nanocomposites (C-NCs) were investigated and the C-NCs were found to posses the resistance of 1.08 × 108 Ω at 1 wt% NGPs loading. The C-NCs with fast response (∼3 s), rapid recovery (∼60 s) and excellent repeatability at room temperature provide novel materials for chemiresistive sensors for detection of H2O2 vapors.

Synthesis, Characterization and Swelling Characteristics of Graft Copolymerized Isotactic Polypropylene Film

Grafted membranes were prepared through chemical graft copolymerization of methyl methacrylate (MMA) onto isotactic polypropylene film (IPP). The IPP films were grafted with MMA molecules resulting in IPP-g-MMA grafts using benzoyl peroxide as an initiator in an inert nitrogen atmosphere. Using this method, the degree of grafting and morphology could be controlled through the variation of reaction parameters such as initiator concentration, monomer concentration, reaction time, and the reaction temperature. Optimum conditions pertaining to maximum percentage of grafting (%G) were evaluated as a function of these parameters. Maximum percentage of grafting (50%) was obtained at [BPO]=0.03 M, [MMA]=10% V/V, and [Reaction Temperature] = 70∘C in a [Reaction time] of 120 minutes. IPP-g-MMA films were investigated for their swelling behavior. Water-swelling analysis of IPP-g-MMA was carried out as a function of different percentage of grafting, temperatures, and time. Maximum swelling percentage of IPP-g-MMA (92%) was observed in 8 hours at 60∘C. The evidence of grafting was carried out by Fourier transform spectroscopy (FTIR), atomic force microscopy (AFM), and scanning electron microscopy (SEM) before and after grafting, respectively. The swelling pattern was characterized by two distinct stages, an initial diffusion-controlled fast swelling, followed by a subsequent slower process controlled by the relaxation of polymer fragments. Swelling chrematistics of IPP-g-MMA make it a potentially useful material.

Strategy to synthesise nano-engineered polymer nanocomposite with a mechanically strong interface: a highly flexible ammonia gas sensor

The work reported herein describes a facile strategy for synthesize of a highly flexible and free standing novel polymethyl methacrylate/nanographite platelets nanocomposite (P-NC) film through click chemistry. The unique concept involves the formation of P-NCs which not only imparts the strong covalent interaction between the azide functionalized polymethyl methacrylate (Az-f-PMMA) and alkyne functionalized nanographite platelets (Alk-f-NGPs) at the interface through triazole linkages but also enhances the exfoliation of NGPs within the polymer matrix. Thus, the synergy between the polymer and the NGPs through the high density of interfaces results in remarkable electrical, mechanical and sensing properties. The structure and micromorphology of the prepared P-NCs were confirmed by FTIR, NMR, XPS, UV spectroscopy, Raman spectroscopy, XRD, TGA, SEM, TEM and AFM techniques. A maximum indentation elastic modulus (E) of 4.1 GPa and hardness (H) of 0.23 GPa were obtained for P-NC with an ultralow loading of 0.1% NGPs, as compared to 3.3 GPa and 0.17 GPa, respectively, for pure PMMA. The flexible, robust P-NC films demonstrated excellent sensing properties towards ammonia vapor with fast response and recovery, both at room temperature (response = ∼2 s, recovery = ∼32 s) as well as at 0 °C (response = ∼1 s, recovery = ∼13 s). The work reported opens up new opportunities for the development of robust and portable P-NC sensors which can detect ammonia vapor in refrigeration plants where leakage should be indicated both at low temperature near the valves, as well as room temperature in the surrounding atmosphere, having flexibility to be fabricated in any shape as per the positioning of the sensor in the refrigeration plant.

Modification of PMMA/graphite nanocomposites through ion beam technique

Swift heavy ion (SHI) irradiation is a special technique for inducing physical and chemical modifications in bulk materials. In the present work, the SHI hs been used to prepare nanocomposites with homogeneously dispersed nanoparticles. The nanographite was synthesized from graphite using the intercalation–exfoliation method. PMMA Poly(methyl methacrylate)/graphite nanocomposites have been synthesized by in situ polymerization. The prepared PMMA/graphite nanocomposite films were irradiated with SHI irradiation (Ni ion beam, 80 MeV and C ion beam, 50 MeV) at a fluence of 1×1010 to 3×1012 ions/cm2. The nanocomposite films were characterized by scanning electron microscope (SEM) and were evaluated for their electrical and sensor properties. After irradiation, significant changes in surface morphology of nanocomposites were observed as evident from the SEM images, which show the presence of well-distributed nanographite platelets. The irradiated nanocomposites exhibit better electrical and sensor properties for the detection of nitroaromatics with marked improvement in sensitivity as compared with unirradiated nanocomposites.

Biodegradable Nanocomposites for Energy Harvesting, Self-healing, and Shape Memory

This review aims to survey the rapidly expanding field of energy harvesting, self-healing, and shape-memory biodegradable composites by reviewing the major successful autonomic designs developed over the last decade. We have discussed the characterization of the composite and dispersion of the filler by different methods such as grafting, chemical modifications. Also, we have highlighted the recent work on polymers and blends, hydrogels of biocomposites and their controllable approach for adjusting desired properties. In addition to above, the design considerations critical to the successful integration of these components in the commercial applications have been discussed. These materials have huge demand in the development of robust modeling and design tools based on a fundamental understanding of the complex and time-variant properties of the material and mechanization structure in diverse environments. The potential directions for future advancement in this field are also discussed.

Polypropylene/Glass Fiber Composites for Low Cost Orthotic Aid

Orthotic aid is an externally applied device used to modify the structural and functional characteristics of the neuromuscular and skeletal system. The orthotic devices are fabricated using polymer resins such as HDPE, polypropylene, acrylics etc. of which polypropylene (PP) is the most widely accepted material for this application. However, the limitations associated with polypropylene devices are decreased durability because of material tears or splits. In the present work, silanized glass fibers (GF) of varied length were used to reinforce and improve the performance of PP for fabricating polypropylene-glass fiber (PP-GF) composites through melt blending process, which provides high performance orthotic aid material with dramatic improvement in properties such as strength, stiffness, dimensional stability etc. Maleic anhydride grafted PP (PP-g-MAH) was used as compatibilizer to improve the compatibility between PP and silanized GFs in the composite. The PP-GF composites were characterized with Scanning electron microscopy (SEM) and Fourier Transform Infra Red spectroscopy (FTIR). Mechanical properties of PP-GF composites was investigated as per ASTM standards. Mechanical studies claimed that the hardness, tensile properties, of PP-GF composites increases over PP-resin, while elongation at break and impact strength decreases. Compatibilized PP-GF composites reinforced with 10 wt% GFs with elongation at break ~50 % at room temperature, showed improved mechanical performance over PP resin, which makes them suitable material for developing orthotic aid. Thus, PP-GF composites will offer lighter, stronger orthotic devices at lower cost.

Pine Needles as Green Material for Removal of Metal Ions and Dyes from Waste Water

Carcinogenic properties of Chromium(VI) have been studied extensively and reported. The majority of the environmental releases of chromium are from industrial sources. Rhodamine B is a synthetic dye widely used as colourant in the manufacture of textiles and food stuffs. Rhodamine dyes present in drinking water could lead to subcutaneous tissue borne sarcoma which is highly carcinogenic. Other toxicities like reproductive and neurotoxicity have been investigated and proved. The work reported involves the removal of Cr(VI) as well as Rhodamine B dye using pine needles by the process of adsorption. The adsorption studies were performed by batch process and the detection done using UV–visible spectrophotometer at 540 nm for Cr(VI) and 554 nm for Rhodamine B. Various parameters like pH, concentration of adsorbent, mass of adsorbate, time of contact were optimized. The percentage efficiency for removal under optimized conditions, of Cr(VI) and Rhodamine B dye was up to 96 and 92% respectively. The adsorption studies were performed using Freundlich and Langmuir adsorption isotherms as well as the kinetic and thermodynamic parameters have also been determined. This technique can be effectively used for the detoxification of water by the removal of metal ions and dyes obtained from industries.

Tunable Mechanical, Electrical, and Thermal Properties of Polymer Nanocomposites through GMA Bridging at Interface

Polymer nanocomposites (PNCs) have become an exciting field of current research and have attracted a huge interest among both academia and industry during the last few decades. However, the multifunctional single-nanocomposite film exhibiting the combination of desired structure and properties still remains a big challenge. Herein, we report a novel strategy to address these problems by using versatile polymer glycidyl methacrylate (GMA) as a bridging medium between the filler and the polymer matrix, resulting in high density of interfaces as well as strong interactions, which lead to generation of tunable thermal, mechanical, and electrical properties in the materials. The nanocomposites prepared by GMA bridging exhibit the remarkable combination of thermal (Td = 342.2 °C, Tg = 150.1 °C ), mechanical (E = 7.6 Gpa and H = 0.45 Gpa ) and electrical (σ = 3.15 × 10−5 S/cm) properties. Hence, the conjugation approaches related to GMA bridging facilitate a new paradigm for producing multifunctional polymer nanocomposites having a unique combination of multifunctional properties, which can be potentially used in next-generation polymer-based advanced functional devices.

Improved Electrical and Thermal Properties of TETA Functionalized NGPs/Epoxy Nanocomposites

The present work reports the synthesis of nanocomposites (NCs) prepared by amine functionalization of nanographite platlets (NGPs) coupled with diglycidyl ether of bisphenol A (DGEBA) epoxy resin. NGPs were treated with 3:1 mixture of concentrated H2SO4/HNO3, and then grafted with triethylene-tetramine (TETA) that contributes uniform dispersion of NGPs within the epoxy matrix. In particular, the amine functionalization of NGPs with triethylene-tetramine (TETA) purposed to attain better dispersion and strong interfacial interaction between the filler and the matrix. The TETA functionalized NGPs/epoxy nanocomposites (DGEBA/TETA-NGPs) were produced by molding curing method. The synthesized nanocomposites were characterized by FTIR and SEM techniques. The electrical and thermal properties of the nanocomposites at various TETA-NGP loadings were investigated and found to attain an increase in the conductivity and thermal stability compared with that of neat epoxy resin.