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Coherent X-ray scattering reveals nature of dynamical transitions in nanoparticle-polymer suspensions

Chandran, Sivasurender and Begam, N and Sprung, M and Basu, JK (2016) Coherent X-ray scattering reveals nature of dynamical transitions in nanoparticle-polymer suspensions. In: POLYMER, 105 (SI). pp. 500-509.

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Official URL: http://dx.doi.org/10.1016/j.polymer.2016.07.048

Abstract

We report the microrheological behavior and dynamics of the suspensions of polystyrene-grafted gold nanoparticles (PGNPs) mixed with linear polystyrene (PS) as a function of the PS concentration and size asymmetry parameter, xi (=M-g/M-m, with M-g and M-m being the grafted and free chain molecular weights, respectively) = 2.76 and 0.14. Diffusive wave spectroscopy (DWS) is used for measuring the frequency dependent micro-rheology parameter, the loss modulus G `'(omega))(-omega(alpha)). For suspensions with xi = 0.14 a transition of alpha, from similar to 1 to similar to 1.6, is observed at a critical fraction of added polymers. On the other hand, alpha is always similar to 1 for the suspensions with xi = 2.76. Corresponding x-ray photon correlation spectroscopy (XPCS) data on the same samples reveals a sharp transition in the nature of dynamics of PGNPs, from exponential to logarithmic, in suspensions with xi = 0.14, while for suspensions with E = 2.76 this dynamical transition is not observed. Interestingly, the dynamical transition in xi = 0.14 based samples occurs at the same fraction of added polymers, where the transition of a from similar to 1 to similar to 1.6 was observed, thus providing a clear correlation between microscopic dynamics and micro-rheology. The conformational transitions of the grafted polymers is found to be the reason behind the observed differences in the dynamic behavior of the two systems. The important role of advanced x-ray scattering techniques in unravelling subtle aspects of nanoscale complex polymer and soft colloidal dynamics is thus revealed. (C) 2016 Elsevier Ltd. All rights reserved.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the ELSEVIER SCI LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Depositing User: Id for Latest eprints
Date Deposited: 20 Jan 2017 04:18
Last Modified: 25 Feb 2019 10:36
URI: http://eprints.iisc.ac.in/id/eprint/55922

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