Fong, Rebecca and Squillace, Ophélie and Reynolds, Carl and Cooper, Joshaniel and Dalgliesh, Robert Malcolm and Tellam, James and Courchay, Florence and Thompson, Richard L. (2020) 'Segregation of amine oxide surfactants in PVA films.', Langmuir., 36 (17). pp. 4795-4807.
The vertical depth distributions of amine oxide surfactants, N,N-dimethyldodecyl amine N-oxide (DDAO) and N,N-dimethyltetradecyl amine N-oxide (DTAO), in poly(vinyl alcohol) (PVA) films were explored using neutron reflectometry (NR). In both binary and plasticized films, the two deuterated surfactants formed a single monolayer on the film surface with the remaining surfactant homogeneously distributed throughout the bulk of the film. Small-angle neutron scattering and mechanical testing revealed that these surfactants acted like plasticizers in the bulk, occupying the amorphous regions of PVA and reducing its glass-transition temperature. NR revealed little impact of plasticizer (glycerol) incorporation on the behavior of these surfactants in PVA. The surfactant molecular area in the segregated monolayer was smaller for DTAO than for DDAO, indicating that the larger molecule was more densely packed at the surface. Surface tension was used to assess the solution behavior of these surfactants and the effect of glycerol incorporation. Determination of molecular area of each surfactant on the solution surface revealed that the structures of the surface monolayers are remarkably consistent when water is placed by the solid PVA. Incorporation of glycerol caused a decrease of molecular area for DDAO and increase in molecular area for DTAO both in solution and in PVA. This suggests that the head group interactions, which normally limit the minimum area per adsorbed molecule, are modified by the length of the alkyl tail.
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|Publisher Web site:||https://doi.org/10.1021/acs.langmuir.0c00084|
|Publisher statement:||This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.|
|Date accepted:||30 March 2020|
|Date deposited:||06 May 2020|
|Date of first online publication:||09 April 2020|
|Date first made open access:||06 May 2020|
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