Rajalakshmi Chockalingam

Bio: Rajalakshmi Chockalingam is an academic researcher from Indian Institutes of Technology. The author has contributed to research in topics: Solvation & Aqueous solution. The author has an hindex of 3, co-authored 5 publications receiving 38 citations.

Self-association behaviour of atactic polymethacrylic acid in aqueous solution investigated by atomistic molecular dynamics simulations

Abstract: The self-association behaviour of atactic poly(methacrylic acid) (a-PMA) in water was investigated by atomistic molecular dynamics (MD) simulations. Simulations show that interchain association of a-PMA occurs only in its un-neutralised form, by hydrogen bonding between –COOH groups, which is in agreement with the experimental observation. Chain conformations, dihedral angle distributions, hydration behaviour, scattering structure factor and enthalpy-of-hydration (i.e. aqueous solvation) were analysed as a function of concentration for un-neutralised PMA, across dilute to concentrated regimes. The average 〈Rg〉 of the chain remains unaffected in solution and also for amorphous undissolved a-PMA phase, confirming the occurrence of the approximate theta-solution condition for the first time, as revealed by simulations, in a polar hydrogen-bonding polymer aqueous solution. Chain hydration behaviour and scattering structure factor show significant changes in concentrated regime. Scattering intensity collapse o...

Dynamics of conformations, hydrogen bonds and translational diffusion of poly(methacrylic acid) in aqueous solution and the concentration transition in MD simulations

Abstract: The dynamic behaviour of chain conformations, hydrogen bonds and translational diffusion of aqueous poly(methacrylic acid) (PMA) solution as a function of polymer volume fraction Φp across dilute to concentrated regimes inclusive of the pure polymer amorphous state was studied by molecular dynamics simulations. The behaviour of the relaxation time (τ) of the backbone dihedral angle auto-correlation function (ACF) reveals slower relaxation at higher level of polymer concentration and the existence of a concentration-driven relaxation transition for the aqueous polymer solution which occurs in the polymer volume fraction range, specifically 54% < Φp < 82% for this system. The relaxation constant τ for backbone dihedral angle exhibits a linear variation with Φp, indicating a first-order kinetic transition. The intermittent ACF for decay of the H-bond correlation shows that H-bonds among water molecules relax faster than those of the PMA–PMA and PMA–water type. The relaxation rate of PMA–water H-bonds shows a...

Molecular dynamic simulations study of the effect of salt valency on structure and thermodynamic solvation behaviour of anionic polyacrylate PAA in aqueous solutions

Abstract: The effect of salt concentration and valency on intermolecular structure and solvation thermodynamic properties of aqueous solution containing polyacrylicacid (PAA) chains and multi-valent salts calcium chloride (CaCl2) and aluminium chloride (AlCl3) as a function of charge density was investigated using atomistic molecular dynamic simulations with explicit solvent. Salt-free solution favours the self-association of uncharged (acidic form) PAA chains facilitated by inter-chain hydrogen bonds. The ionised (charged) PAA chains are not associated in salt-free aqueous solutions and undergo self-association in the salt solutions due to bridging effect induced by condensed salt ions in agreement with scattering investigations available in literature. The collapse behaviour of PAA in presence of CaCl2 and re-expansion behaviour of PAA chains in case of AlCl3 salt solutions are observed. The rigidity of PAA chains decrease with increase in salt concentration, in agreement with experimental results availab...

Molecular Dynamics Simulations Investigation of Structure and Thermodynamic Properties of Symmetric Poly(styrene-block-acrylic acid) (PS-b-PAA) Micelle in Salt-Free Aqueous Solution

Abstract: The structure and thermodynamic aspects of symmetric poly(styrene-block-acrylicacid)(PS-b-PAA) copolymer micelle in salt-free aqueous solution as a function of ionization (f) of PAA was probed by molecular dynamics simulations. Quantitative comparison of micelle radius shows that the GROMOS parameter set gives the best agreement with experiment. As f increases, Micelle size increases, attains spherical shape, PS surface area increases, and PAA water hydrogen-bonds increases. Pair correlation functions and solvation enthalpy show that PS interactions are insensitive to f. Density profiles and solvation enthalpy of PAA–Na+, water–Na+ pairs confirm the micelle being in the “osmotic regime” experiments.

Introduction To Polymers

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Diffusion characteristics of asphalt rejuvenators based on molecular dynamics simulation

Abstract: In recent years, the regeneration technology of aged asphalt in construction engineering has received much attention. The diffusion performance of the rejuvenator is a key factor in this kind of re...

Study of diffusion characteristics of asphalt–aggregate interface with molecular dynamics simulation

Abstract: The generation and development of interfacial adhesion properties between the asphalt binder and the aggregate surface is difficult to explain at the microscale through experiments. In this researc...