Kamath, Ganesh; Deshmukh, Sanket A.; Baker, Gary A.; Mancini, Derrick C.; Sankaranarayanan, Subramanian K. R. S.
Thermodynamic considerations for solubility and conformational transitions of poly-N-isopropyl-acrylamide
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15:12667-12673, 2013

Thermodynamic considerations based on the free energy of hydration, free energy of solvation and partition coefficient predictions of the monomer N-isopropyl-acrylamide (NIPAM) determined using various intermolecular potentials are used to elucidate the origin of hydrophobicity/hydrophilicity across the lower critical solution temperature (LCST). Thermodynamic properties are predicted for NIPAM using adaptive bias force-molecular dynamics and various popular force-fields (AMBER, OPLS-AA, CHARMM and GROMOS) at four different temperatures: below the LCST (275 K and 300 K) and above the LCST (310 K and 330 K). The effect of changes in the thermodynamic properties of the monomer NIPAM at various temperatures below and above LCST on the kinetics of conformational transition of thermo-sensitive polymers is discussed. Our findings provide encouraging prospects for understanding the LCST transition in the hydrogel poly-N-isopropylacrylamide which shows temperature-dependent conformational changes in part due to the complex interplay of hydrophilic/hydrophobic interactions.

DOI:10.1039/c3cp44076a

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