Microscopic temperature-dependent structural dynamics in polymer nanocomposites: role of the graft-matrix chain interfacial entropic effect

Swain, A and Nimmi Das, A and Sakai, VG and Basu, JK (2023) Microscopic temperature-dependent structural dynamics in polymer nanocomposites: role of the graft-matrix chain interfacial entropic effect. In: Soft Matter .

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Abstract

We present a systematic study of the structural dynamics in bulk entropic polymer nanocomposites (PNCs) with deuterated-polymer-grafted nanoparticles (DPGNPs) using quasi-elastic neutron scattering (QENS). We observe that the wave-vector-dependent relaxation dynamics depend on the entropic parameter f as well as the length scale being probed. The entropic parameter can be defined in terms of the grafted-to-matrix polymer molecular weight ratio and controls the extent of matrix chain penetration into the graft. Dynamical cross-over from Gaussian to non-Gaussian behavior at the wave vector Qc, which depends on temperature and f, was observed. Further insight into the underlying microscopic mechanism responsible for the observed behavior revealed that when interpreted using a jump-diffusion model, in addition to the speeding-up in local chain dynamics, the elementary distance over which sections of the chain hop is strongly dependent on f. Interestingly, we also observe dynamic heterogeneity (DH) in the studied systems, characterized by the non-Gaussian parameter α2, which reduces for a high-f (f = 0.225) sample compared with the pristine host polymer, indicating reduced dynamical heterogeneity, while it is mostly unchanged for the low-f sample. The results highlight that, unlike enthalpic PNCs, entropic PNCs with DPGNPs can modify the host polymer dynamics due to the subtle balance of interactions that occur at different length scales in the matrix.

Item Type:	Journal Article
Publication:	Soft Matter
Publisher:	Royal Society of Chemistry
Additional Information:	The copyright for this article belongs to the Royal Society of Chemistry.
Keywords:	Dynamics; Entropy; Gaussian noise (electronic); Grafting (chemical); Nanocomposites; Neutron scattering; Polymer matrix composites, Entropic effects; Host polymers; Matrix chain; Polymer nanocomposite; Polymer-grafted nanoparticles; Polymer-nanocomposite; Quasielastic neutron scattering; Systematic study; Temperature dependent; Wave-vector-dependent relaxation, Structural dynamics
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	04 Aug 2023 10:09
Last Modified:	04 Aug 2023 10:09
URI:	https://eprints.iisc.ac.in/id/eprint/82850

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