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Agglomeration Dynamics In Thermo-Sensitive Polymers Across TheLower Critical Solution Temperature: A Molecular Dynamics SimulationStudy

Published online by Cambridge University Press:  03 February 2012

Sanket A. Deshmukh ,
Subramanian K.R.S. Sankaranarayanan  and
Derrick C. Mancini
Sanket A. Deshmukh
Affiliation:
Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL 60439
Subramanian K.R.S. Sankaranarayanan
Affiliation:
Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL 60439
Derrick C. Mancini
Affiliation:
Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439
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Abstract

Poly(N-isopropylacrylamide) (PNIPAM), a classic thermo-sensitive polymer,has a lower critical solution temperature (LCST) at ∼32°C. In this work wehave used molecular dynamics simulations to understand the origin of theLCST and agglomeration of PNIPAM chains of 5 and 30 monomer units (5-mer and30-mer). Experimentally, when the concentration of PNIPAM is >1 ppm,polymer chains after undergoing coil-to-globule transition above the LCSTaggregates to yield a stable colloidal dispersion.In our study two PNIPAMchains, consisting of 30 monomer units each, were placed in a cubicsimulation cell and were subsequently solvated. Simulations were carried outbelow and above the LCST, namely at 278 and 310K for 10ns. Simulatedtrajectories were analyzed for structural and dynamical properties of bothPNIPAM and water. We observe coil-to-globule transition in PNIPAM above theLCST. We also find that the PNIPAM chains agglomerate above the LCST. Wealso observe entanglement in PNIPAM chains below the LCST. We also studyagglomeration of 5 PNIPAM chains each consisting of 5 monomer units. Therewas no significant difference in polymer agglomeration behavior across theLCST for these short chain oligomers. The agglomeration behavior is thusstrongly correlated to the size of the polymer chains. These results providefundamental insight into the atomistic scale mechanism of PNIPAMagglomeration across the LCST.

Keywords

polymerbiomedicalsimulation

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Type
Articles
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MRS Online Proceedings Library (OPL) , Volume 1418: Symposium LL/MM – Gels and Biomedical Materials , 2012 , mrsf11-1418-ll07-06
Copyright
Copyright © Materials Research Society 2012

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References

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