Sujitkumar Bontapalle

Bio: Sujitkumar Bontapalle is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: PEDOT:PSS & Gibbs free energy. The author has an hindex of 2, co-authored 4 publications receiving 10 citations.

Molecular Thermodynamics of Polymer Chains Confined between Planar Surfaces Bearing End-Tethered Flexible Molecules

Abstract: A lattice-based model of the confinement of homopolymer free chains between two flat solid surfaces, each covered with end-tethered flexible chains, is developed. The free energy and free energy change for the formation of the confined state from reference states of the different components are calculated based on lattice and scaling theory concepts. Entropic and energetic factors determine the free energy of the system. The dependency of free energy and free energy change on the chain lengths (molecular weights) of free polymers and tethered polymers, the density of end-tethered chains on the surfaces, the distance between the surfaces, and the various intersegment interaction energy parameters for various component species, were studied. The phase diagrams obtained in this work provide ways for designing thermodynamically stable systems in various regimes. The results are qualitatively in agreement with those from earlier models based on self-consistent field theory and experiments.

Thermodynamic Free Energy Behavior of Diblock Copolymer Chains Confined Between Planar Surfaces Having End-Tethered Flexible Polymer Molecules

Abstract: A molecular model for the free energy of a confined system of diblock copolymer chains within a 2D slit with the interior surfaces having end-tethered chains is presented, based on a combined lattice and scaling theory approach. The thermodynamics of a model system, based on a constrained minimization of free energy, is explored as a function of the intermolecular energy parameters for interaction between the segments of block copolymer chains, end-tethered chains, and the surfaces. The effects of chain length and the block length ratio are investigated over a wide range of values. The results obtained are qualitative in nature; however, the model can be implemented to real systems provided appropriate parameterization of the model parameters to real systems can be performed. The phase diagrams obtained here provide ways for designing thermodynamically stable systems within the physical parametric variable space.

Molecular Dynamics Study of the Intercalation of Diblock Copolymers into Layered Silicates

Abstract: Polymer-layered silicate nanocomposites may be formed by annealing layered silicate particles with a polymer melt. Polymer molecules flow from a bulk melt into the galleries between silicate sheets, swelling the silicate structure. The use of an amphiphilic intercalant raises possibilities of forming novel structures and enhancing the intercalation kinetics relative to the case of homopolymer intercalants. We perform molecular dynamics simulations of the flow of a symmetric diblock copolymer from a bulk melt into a slit whose surfaces are modified by grafted surfactant chains, and whose walls are maintained at a constant pressure to permit the slit to open as polymer intercalates. Intercalation kinetics are examined for a variety of polymer–surface and interblock interactions and for thermodynamic states in which the bulk polymer occupies either a lamellar or disordered phase. Comparison to previous simulations of homopolymer intercalation demonstrates that diblock copolymers may be used to intercalate a block that would not spontaneously intercalate as a homopolymer.

Highly Stretchable and Flexible Melt Spun Thermoplastic Conductive Yarns for Smart Textiles.

Abstract: This study demonstrates a scalable fabrication process for producing biodegradable, highly stretchable and wearable melt spun thermoplastic polypropylene (PP), poly(lactic) acid (PLA), and composite (PP:PLA = 50:50) conductive yarns through a dip coating process. Polydopamine (PDA) treated and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) coated conductive PP, PLA, and PP/PLA yarns generated electric conductivity of 0.75 S/cm, 0.36 S/cm and 0.67 S/cm respectively. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the interactions among the functional groups of PP, PLA, PP/PLA, PDA, and PEDOT:PSS. The surface morphology of thermoplastic yarns was characterized by optical microscope and Scanning Electron Microscope (SEM). The mechanical properties of yarns were also assessed, which include tensile strength (TS), Young’s modulus and elongation at break (%). These highly stretchable and flexible conductive PP, PLA, and PP/PLA yarns showed elasticity of 667%, 121% and 315% respectively. The thermal behavior of yarns was evaluated by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Wash stability of conductive yarns was also measured. Furthermore, ageing effect was determined to predict the shelf life of the conductive yarns. We believe that these highly stretchable and flexible PEDOT:PSS coated conductive PP, PLA, and PP/PLA composite yarns fabricated by this process can be integrated into textiles for strain sensing to monitor the tiny movement of human motion.

Dramatic Responsivity Enhancement Through Concentrated H2SO4 Treatment on PEDOT:PSS/TiO2 Heterojunction Fibrous Photodetectors

Abstract: In order to satisfy the growing requirements of wearable electronic devices, 1D fiber-shaped devices with outstanding sensitivity, flexibility, and stability are urgently needed. In this study, a novel inorganic-organic heterojunction fibrous photodetector (FPD) based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and highly ordered TiO2 nanotube array is fabricated, which endows a high responsivity, large external quantum efficiency, and fast response speed at 3 V bias. To further ameliorate its performance in the self-powered mode, a facile acid treatment is adopted and the assembled H-PEDOT:PSS/TiO2 FPD demonstrates outstanding self-powered properties with ≈3000% responsivity enhancement (161 mA W-1 at 0 V under 365 nm irradiation, photocurrent enhancement of ≈50 times) compared with the untreated device. It is found that the concentrated H2 SO4 post-treatment helps decrease the tube wall thickness of TiO2 and partially removes the insulated PSS component in PEDOT:PSS, leading to enhanced conductivity and facilitated charge transportation, and thereby superb responsivity/photocurrent enhancement of self-powered H-PEDOT:PSS/TiO2 FPD. This low-cost and high-performance self-powered FPD shows high potential for applications in wearable electronic devices.

Oxidative photopolymerization of 3,4-ethylenedioxythiophene (EDOT) via graphitic carbon nitride : a modular toolbox for attaining PEDOT

Abstract: Conductive polymers find key applications ranging from optoelectronics and OLEDs to conductive composite materials. The synthesis of conductive polymers from monomers, such as thiophene derivatives, pyrroles and aniline, mainly relies on oxidative polymerization, and the processing of so-formed (insoluble) polymers is a major issue that needs to be addressed. In the present work, oxidative photopolymerization of 3,4-ethylenedioxythiophene (EDOT) by visible light employing the metal-free semiconductor graphitic carbon nitride (gCN) is presented. Two main reaction pathways based on g-CN content are described, and the formation of processable oligoEDOT is demonstrated.