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Issue 12, 2016
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Molecular dynamics study of wetting behavior of grafted thermo-responsive PNIPAAm brushes

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Abstract

In this work, the effect of temperature on the contact angle of a water droplet on grafted thermo-responsive poly-(N-isopropylacrylamide) (PNIPAAm) polymer brushes is studied using all-atom molecular dynamics simulations in the temperature range of 270–330 K. A shift from 55° to 65° in contact angle values is observed as the temperature increases from 300 K to 310 K, which is in line with the experimental reports. The behavior of a water droplet on PNIPAAm brushes is analyzed using hydrogen bond analysis, water diffusion, radial distribution functions, the potential of mean force, excess entropy and the second virial coefficient (B2). The thermo-responsive behavior of PNIPAAm brushes, quantified using the excess entropy and B2 of PNIPAAm–water and water–water interactions, is mainly governed by polymer–water interactions. In particular, the excess entropy and B2 of PNIPAAm resulting from the PNIPAAm–water interactions are found to increase with increasing temperature. The dehydration of PNIPAAm brushes and the increase in the contact angle of water were confirmed to be entropy driven processes.

Graphical abstract: Molecular dynamics study of wetting behavior of grafted thermo-responsive PNIPAAm brushes

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Article information


Submitted
30 Oct 2015
Accepted
25 Jan 2016
First published
28 Jan 2016

Soft Matter, 2016,12, 3093-3102
Article type
Paper
Author version available

Molecular dynamics study of wetting behavior of grafted thermo-responsive PNIPAAm brushes

D. Bhandary, Z. Benková, M. N. D. S. Cordeiro and J. K. Singh, Soft Matter, 2016, 12, 3093
DOI: 10.1039/C5SM02684A

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