(556e) All-Atom Molecular Dynamics Simulations of Poly(N-isopropylacrylamide) Grafted Architectures

All-atom Molecular Dynamics
Simulations of Poly(N-isopropylacrylamide)
Grafted Architectures

Ganesh Kamath³, Sanket A. Deshmukh¹, Derrick C.
Mancini², Subramanian K.R.S. Sankaranarayanan¹

¹Center for Nanoscale Materials, Argonne National
Laboratory, Argonne, IL 60439

²Physical Sciences and Engineering, Argonne National Laboratory,
Argonne, IL 60439

³Department of Chemistry, University of Missouri-Columbia,
Columbia 65211

Poly(N-isopropylacrylamide)
(PNIPAM) is a thermosensitive polymer that is
well-known for its lower critical solution temperature (LCST) around 305K.
Below the LCST, PNIPAM is soluble in water, and above this temperature, polymer
chains collapse and transform into a globule-state. In this study, we have
carried out MD simulations of PNIPAM polymer chains consiting
of 60 monomer units grafted on a gold nanoparticle
and a planar surface to study the effect of curvature and temperature on the
polymer conformations. We have also studied effect of grafting density and size
of nanoparticle on the coil-to-globule collapse shown
by PNIPAM above the LCST. Studied system consisted of 100 K to ~3 million atoms.
All the simulations were carried out below and above the LCST of PNIPAM, namely, at 275 and 325 K. Simulation trajectories
were analyzed for structural and dynamical properties such as radius of
gyration of PNIPAM chains, hydrogen bond life-times, and residence time
probability of water molecules.

Use of the Center for Nanoscale
Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No.
DE-AC02-06CH11357.

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Argonne National Laboratory ("Argonne"). Argonne, a U.S. Department
of Energy Office of Science laboratory, is operated under Contract No.
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