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Molecular dynamics simulations of PAA – PMA polyelectrolyte copolymers in dilute aqueous solution / Muralidharan S. Sulatha in Industrial & engineering chemistry research, Vol. 51 N° 33 (Août 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 33 (Août 2012) . - pp. 10833–10839 Titre : Molecular dynamics simulations of PAA – PMA polyelectrolyte copolymers in dilute aqueous solution : Chain conformations and hydration properties Type de document : texte imprimé Auteurs : Muralidharan S. Sulatha, Auteur ; Upendra Natarajan, Auteur Année de publication : 2012 Article en page(s) : pp. 10833–10839 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Dynamics  simulations  Aqueous  solution Résumé : Atomistic molecular dynamics simulations of copolymers of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMA) in dilute aqueous solution were performed as a function of charge density, in explicit solvent medium and counterions. The studied polyelectrolytes follow a general behavior of chain expansion with charge density until a point where the repulsion between the electrostatic charges between the anionic residues is effectively neutralized by the counterions. The average persistence length is found to increase and levels off at higher charge densities, and the values imply the chains to be flexible. With increase in PMA content in the chain, counterions show increased correlation with chain backbone and a systematic reduction in the number of water molecules in the first hydration shell. The intermittent hydrogen-bond correlation function for the hydrogen bonds between the chain residues and water decays faster for PAA chain as compared to PMA, indicating a rigid hydration layer for the latter. The shorter H-bond lifetimes coupled with the slower relaxation indicate that MA–water H-bonds break more easily than those of AA–water H-bonds, but the water molecules remain in the vicinity of the chain because of slow diffusivity and can easily reform the bonds. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie301244n [article] Molecular dynamics simulations of PAA – PMA polyelectrolyte copolymers in dilute aqueous solution : Chain conformations and hydration properties [texte imprimé] / Muralidharan S. Sulatha, Auteur ; Upendra Natarajan, Auteur . - 2012 . - pp. 10833–10839. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 33 (Août 2012) . - pp. 10833–10839 Mots-clés : Dynamics  simulations  Aqueous  solution Résumé : Atomistic molecular dynamics simulations of copolymers of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMA) in dilute aqueous solution were performed as a function of charge density, in explicit solvent medium and counterions. The studied polyelectrolytes follow a general behavior of chain expansion with charge density until a point where the repulsion between the electrostatic charges between the anionic residues is effectively neutralized by the counterions. The average persistence length is found to increase and levels off at higher charge densities, and the values imply the chains to be flexible. With increase in PMA content in the chain, counterions show increased correlation with chain backbone and a systematic reduction in the number of water molecules in the first hydration shell. The intermittent hydrogen-bond correlation function for the hydrogen bonds between the chain residues and water decays faster for PAA chain as compared to PMA, indicating a rigid hydration layer for the latter. The shorter H-bond lifetimes coupled with the slower relaxation indicate that MA–water H-bonds break more easily than those of AA–water H-bonds, but the water molecules remain in the vicinity of the chain because of slow diffusivity and can easily reform the bonds. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie301244n

Origin of the difference in structural behavior of poly(acrylic acid) and poly(methacrylic acid) in aqueous solution discerned by explicit - solvent explicit - ion MD simulations / Muralidharan S. Sulatha in Industrial & engineering chemistry research, Vol. 50 N° 21 (Novembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 21 (Novembre 2011) . - pp. 11785-11796 Titre : Origin of the difference in structural behavior of poly(acrylic acid) and poly(methacrylic acid) in aqueous solution discerned by explicit - solvent explicit - ion MD simulations Type de document : texte imprimé Auteurs : Muralidharan S. Sulatha, Auteur ; Upendra Natarajan, Auteur Année de publication : 2011 Article en page(s) : pp. 11785-11796 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Aqueous  solution Résumé : The conformational and hydration behavior ofpoly(acrylic acid) (PAA) and poly(methacrylic acid) (PMA) in dilute aqueous solution, as a function of charge density, is studied using two different sets of force field parameters: FF-1 and FF-2. The two sets of force field parameters predict similar correlation distances between carboxylate groups and water. The simulations bring about the difference in the interaction of the counterions with the polyions PAA and PMA. FF-1 predicts that upon neutralization PMA shows stronger correlation with Na+ ions in comparison to PAA in aqueous solution. This difference in behavior agrees with the fact that, in poor solvents, the polyelectrolyte chain and the counterions interact strongly. The atomistic simulations using FF-1 parameters presented here bring about the difference in the conformational behaviors of PAA and PMA and the effect of solvent quality on the polyacrylate chain backbone structure. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24697494 [article] Origin of the difference in structural behavior of poly(acrylic acid) and poly(methacrylic acid) in aqueous solution discerned by explicit - solvent explicit - ion MD simulations [texte imprimé] / Muralidharan S. Sulatha, Auteur ; Upendra Natarajan, Auteur . - 2011 . - pp. 11785-11796. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 21 (Novembre 2011) . - pp. 11785-11796 Mots-clés : Aqueous  solution Résumé : The conformational and hydration behavior ofpoly(acrylic acid) (PAA) and poly(methacrylic acid) (PMA) in dilute aqueous solution, as a function of charge density, is studied using two different sets of force field parameters: FF-1 and FF-2. The two sets of force field parameters predict similar correlation distances between carboxylate groups and water. The simulations bring about the difference in the interaction of the counterions with the polyions PAA and PMA. FF-1 predicts that upon neutralization PMA shows stronger correlation with Na+ ions in comparison to PAA in aqueous solution. This difference in behavior agrees with the fact that, in poor solvents, the polyelectrolyte chain and the counterions interact strongly. The atomistic simulations using FF-1 parameters presented here bring about the difference in the conformational behaviors of PAA and PMA and the effect of solvent quality on the polyacrylate chain backbone structure. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24697494