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Article

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

1
Department of Chemistry, Durham University, Durham DH1 3LE, UK
2
STFC ISIS Neutron and Muon Source, Rutherford Appleton Laboratories, Didcot OX11 0QX, UK
3
Procter & Gamble, German Innovation Center, Sulzbacher Str. 40, 65824 Schwalbach am Taunus, Germany
*
Author to whom correspondence should be addressed.
Academic Editor: Marián Lehocký
Polymers 2021, 13(19), 3407; https://doi.org/10.3390/polym13193407
Received: 15 September 2021 / Revised: 28 September 2021 / Accepted: 29 September 2021 / Published: 3 October 2021
(This article belongs to the Section Polymer Membranes and Films)
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. View Full-Text
Keywords: surface modification; hydrophobicity; blooming; segregation; surfactant; poly(isoprene) surface modification; hydrophobicity; blooming; segregation; surfactant; poly(isoprene)
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MDPI and ACS Style

Gibson, C.P.; Litwinowicz, M.A.; Tellam, J.P.; Welbourn, R.J.L.; Skoda, M.W.A.; Claussen, J.; Thompson, R.L. Water-Resistant Surface Modification of Hydrophobic Polymers with Water-Soluble Surfactant Additives. Polymers 2021, 13, 3407. https://doi.org/10.3390/polym13193407

AMA Style

Gibson CP, Litwinowicz MA, Tellam JP, Welbourn RJL, Skoda MWA, Claussen J, Thompson RL. Water-Resistant Surface Modification of Hydrophobic Polymers with Water-Soluble Surfactant Additives. Polymers. 2021; 13(19):3407. https://doi.org/10.3390/polym13193407

Chicago/Turabian Style

Gibson, Colin P., Matthew A. Litwinowicz, James P. Tellam, Rebecca J.L. Welbourn, Maximilian W.A. Skoda, Jan Claussen, and Richard L. Thompson 2021. "Water-Resistant Surface Modification of Hydrophobic Polymers with Water-Soluble Surfactant Additives" Polymers 13, no. 19: 3407. https://doi.org/10.3390/polym13193407

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