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Water-Resistant Surface Modification of Hydrophobic Polymers with Water-Soluble Surfactant Additives

Gibson, Colin P.; Litwinowicz, Matthew A.; Tellam, James P.; Welbourn, Rebecca J.L.; Skoda, Maximilian W.A.; Claussen, Jan; Thompson, Richard L.

Water-Resistant Surface Modification of Hydrophobic Polymers with Water-Soluble Surfactant Additives Thumbnail


Authors

Colin P. Gibson

Matthew A. Litwinowicz

James P. Tellam

Rebecca J.L. Welbourn

Maximilian W.A. Skoda

Jan Claussen



Abstract

Water-soluble nonionic surfactant, pentaethylene glycol monododecyl ether, C12E5 , spontaneously blooms to the surface of spin-cast hydrophobic polyisoprenes, generating hydrophilic surfaces. This system provides a simple model for hydrophilic chemical modification of rubbery polymers that demonstrates surprisingly rich, complex, and unexpected behaviour. The vertical depth profiles were quantified using neutron reflectometry (NR) using a novel procedure to account for undulations in the film thickness. Surface properties were characterized using contact angle analysis and atomic force microscopy (AFM). Despite the low surface tension of the toluene solvent used in film preparation and the low surface energy of the polyisoprene (PI) matrix, NR depth profiles revealed clear evidence of surfactant segregation. This surface layer was typically thicker than a monolayer, but incomplete, yet was remarkably stable with respect to dissolution, even when exposed to hundreds of thousands of times the volume of water required to dissolve all the surfactant on the surface. Despite the apparent resistance to removal from the surface, water exposure does alter the subsequent wettability of the surface, with a hydrophilic-to-hydrophobic transition occurring after rinsing. Complementary AFM images of these C12E5/cis-PI films showed unexpected strand-like features on the surface of the film, which we attribute to a non-uniform lateral distribution of some of the surfactant. This surface structure becomes more evident after rinsing, and it appears that there are two distinct populations of surfactant on the PI film surface. We conclude that some of the bloomed surfactant exists as layers, which are relatively inert with respect to rinsing or surface modification, and some is laterally inhomogeneous. This latter population is primarily responsible for surface wetting behaviour but is not detected by specular NR.

Journal Article Type Article
Acceptance Date Sep 29, 2021
Online Publication Date Oct 3, 2021
Publication Date 2021
Deposit Date Oct 7, 2021
Publicly Available Date Oct 7, 2021
Journal Polymers
Publisher MDPI
Peer Reviewed Peer Reviewed
Volume 13
Issue 19
Article Number 3407
DOI https://doi.org/10.3390/polym13193407
Public URL https://durham-repository.worktribe.com/output/1231490

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
© 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).






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