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Lookup NU author(s): Professor Mark Geoghegan
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© 2015 The Royal Society of Chemistry.Measurements have been performed on thermally equilibrated conjugated-polymer/insulating-polymer bilayers, using specular and off-specular neutron reflectivity. While specular reflectivity is only sensitive to the structure normal to the sample, off-specular measurements can probe the structure of the buried polymer/polymer interface in the plane of the sample. Systematic analysis of the scattering from a set of samples with varying insulating-polymer-thickness, using the distorted-wave Born approximation (DWBA), has allowed a robust determination of the intrinsic width at the buried polymer/polymer interface. The quantification of this width (12 Å ± 4 Å) allows us to examine aspects of the conjugated polymer conformation at the interface, by appealing to self-consistent field theory (SCFT) predictions for equilibrium polymer/polymer interfaces in the cases of flexible and semi-flexible chains. This analysis enables us to infer that mixing at this particular interface cannot be described in terms of polymer chain segments that adopt conformations similar to a random walk. Instead, a more plausible explanation is that the conjugated polymer chain segments become significantly oriented in the plane of the interface. It is important to point out that we are only able to reach this conclusion following the extensive analysis of reflectivity data, followed by comparison with SCFT predictions. It is not simply the case that conjugated polymers would be expected to adopt this kind of oriented conformation at the interface, because of their relatively high chain stiffness. It is the combination of a high stiffness and a relatively narrow intrinsic interfacial width that results in a deviation from flexible chain behaviour.
Author(s): James D, Higgins AM, Rees P, Geoghegan M, Brown MR, Chang S-S, Mon D, Cubitt R, Dalgliesh R, Gutfreund P
Publication type: Article
Publication status: Published
Journal: Soft Matter
Print publication date: 28/12/2015
Online publication date: 28/09/2015
Acceptance date: 26/09/2015
Date deposited: 19/12/2019
ISSN (print): 1744-683X
ISSN (electronic): 1744-6848
Publisher: Royal Society of Chemistry
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