pH and generation dependent morphologies of PAMAM dendrimers on a graphene substrate

Gosika, Mounika and Maiti, Prabal K (2018) pH and generation dependent morphologies of PAMAM dendrimers on a graphene substrate. In: SOFT MATTER, 14 (10). pp. 1925-1938.

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Abstract

The adsorption of PAMAM dendrimers at solid/water interfaces has been extensively studied, and is mainly driven by electrostatic and van der Waals interactions between the substrate and the dendrimers. However, the pH dependence of the adsorption driven predominantly by the van der Waals interactions is poorly explored, although it is crucial for investigating the potentiality of these dendrimers in supercapacitors and surface patterning. Motivated by this aspect, we have studied the adsorption behavior of PAMAM dendrimers of generations 2 (G2) to 5 (G5) with pH and salt concentration variation, on a charge neutral graphene substrate, using fully atomistic molecular dynamics simulations. The instantaneous snapshots from our simulations illustrate that the dendrimers deform significantly from their bulk structures. Based on various structural property calculations, we classify the adsorbed dendrimer morphologies into five categories and map them to a phase diagram. Interestingly, the morphologies we report here have striking analogies with those reported in star-polymer adsorption studies. From the fractional contacts and other structural property analyses we find that the deformations are more pronounced at neutral pH as compared to high and low pH. Higher generation dendrimers resist deformation following the deformation trend, G2 > G3 > G4 > G5 at any given pH level. As the adsorption here is mainly driven by van der Waals interactions, we observe no desorption of the dendrimers as the salt molarity is increased, unlike that reported in the electrostatically driven adsorption studies.

Item Type:	Journal Article
Publication:	SOFT MATTER
Publisher:	ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND
Additional Information:	Copy right for this article belong to ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	17 May 2018 18:27
Last Modified:	25 Aug 2022 05:33
URI:	https://eprints.iisc.ac.in/id/eprint/59887

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