Modulating Interdendrimer Interactions through Surface Adsorption

Gosika, M and Mandal, T and Maiti, PK (2020) Modulating Interdendrimer Interactions through Surface Adsorption. In: Langmuir, 36 (20). pp. 5492-5501.

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Abstract

Physical confinement of polymers not only affects their structure but also modifies their effective interaction profiles. In this article, we investigate the nature of graphene-adsorbed poly(amidoamine) (PAMAM) dendrimers' interactions using fully atomistic molecular dynamics simulations. Using the umbrella sampling technique, we calculate the potential of mean force (PMF) profiles for the interaction between two graphene-adsorbed PAMAM dendrimers of generations 3 and 4 as a function of their protonation levels. We find that the attractive PMF profile observed for the interaction between two nonprotonated (high pH) PAMAM dendrimers in bulk becomes repulsive upon adsorption. Also, the repulsive interdendrimer interactions known in bulk for the protonated dendrimers become enhanced for the adsorbed case. We further explain these weakened interactions by explicitly showing that the dendrimer-graphene interaction is an order of magnitude larger than the dendrimer-dendrimer bulk interaction. Using the force integration method, we obtain the contributions from various subinteractions present in the system, that is, dendrimer-water, dendrimer-ions, dendrimer-graphene, and dendrimer-dendrimer to the total PMF. From these contributions, we conclude that the reduced dendrimer-dendrimer interactions in the adsorbed case, as compared to those in bulk, lead to the enhanced repulsive effective interdendrimer interactions. Our PMF profiles fit well with the sum of exponential and Gaussian functions, proposed in the bulk interdendrimer interaction study. We hope the current results provide the microscopic origin of how adsorption weakens the interpolymer interactions in general. © 2020 American Chemical Society.

Item Type:	Journal Article
Publication:	Langmuir
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to American Chemical Society.
Keywords:	Adsorption; Graphene; Molecular dynamics; Protonation, Atomistic molecular dynamics simulations; Effective interactions; Interaction studies; Interpolymer interactions; Physical confinement; Polyamidoamine dendrimers; Potential of mean force; Surface adsorption, Dendrimers
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	06 Feb 2023 08:45
Last Modified:	06 Feb 2023 08:45
URI:	https://eprints.iisc.ac.in/id/eprint/79897

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