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Issue 11, 2018
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Dynamics-based assessment of nanoscopic polymer-network mesh structures and their defects

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Abstract

Polymer-network gels often exhibit complex nanoscopic architectures. First, the polymer-network mesh topology on scales of 1–10 nm is usually not uniform and regular, but disordered and irregular. Second, on top of that, many swollen polymer networks display spatial inhomogeneity of their polymer segmental density and crosslinking density on scales of 10–100 nm. This multi-scale structural complexity affects the permeability, mechanical strength, and optical clarity of the polymer gels, which is of central relevance for their performance in popular applications. As a result, there is a need to characterize the polymer network structures on multiple scales. On the scale of the spatial inhomogeneity of crosslinking, 10–100 nm, scattering of neutrons, X-rays, and light has extraordinary utility and is well established. On the scale of the mesh topology, 1–10 nm, in contrast, experimental techniques are less established. This review intends to close this gap by reviewing two intrinsically dynamic methods that yield information on polymer network mesh structures. First, NMR-based assessment of residual dipolar proton-spin couplings, which arise upon the introduction of crosslinks into a liquidlike polymer system to impart partial solidlike characteristics, is suitable to quantitatively assess network meshes and local network defects. Second, diffusive penetration of molecular, macromolecular, and mesoscopic colloidal probes through a polymer gel provides insight into its obstructing network mesh structure and its potential irregularity. Either method is highly synergistic to scattering-based assessment of the network structures on larger scales, and in concert, a rich picture on the nano- and mesoscopic gel topology is obtained.

Graphical abstract: Dynamics-based assessment of nanoscopic polymer-network mesh structures and their defects

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Article information


Submitted
12 Dec 2017
Accepted
17 Feb 2018
First published
19 Feb 2018

Soft Matter, 2018,14, 1976-1991
Article type
Review Article

Dynamics-based assessment of nanoscopic polymer-network mesh structures and their defects

K. Saalwächter and S. Seiffert, Soft Matter, 2018, 14, 1976
DOI: 10.1039/C7SM02444D

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