Quantifying Gauche Defects and Phase Evolution in Self-Assembled Monolayers through Sessile Drops

dc.contributor.author Chen, Jiahao
dc.contributor.author Chang, Boyce
dc.contributor.author Oyola-Reynoso, Stephanie
dc.contributor.author Thuo, Martin
dc.contributor.author Wang, Zhengjia
dc.contributor.author Thuo, Martin
dc.contributor.department Ames Laboratory
dc.contributor.department Materials Science and Engineering
dc.contributor.department Center for Bioplastics and Biocomposites
dc.date 2018-02-18T18:56:44.000
dc.date.accessioned 2020-06-30T06:07:37Z
dc.date.available 2020-06-30T06:07:37Z
dc.date.copyright Sun Jan 01 00:00:00 UTC 2017
dc.date.issued 2017-01-01
dc.description.abstract <p>Self-assembled monolayers (SAMs) are widely used in surface modifications, specifically in tuning the surface chemistry of materials. The structure and properties of SAMs have been extensively studied often with sophisticated tools, even for the simplest <em>n</em>-alkanethiolate SAMs. In SAMs, especially in linear <em>n</em>-alkanethiolates, the properties are dependent on the chain length, which is best manifested in the so-called odd–even effect, a simple yet not fully understood phenomenon. One main challenge is fully delineating the origin of length-dependent properties, which can be due to the structure (ideal SAMs), defect evolution, or substrate-molecule effects. This study demonstrates that utilizing the wetting behavior of polar (water) and nonpolar (hexadecane (HD)) solvents on <em>n</em>-alkanethiolate SAMs formed on ultraflat gold and silver surfaces, the evolution of chain-length-dependent gauche defects can be revealed and parameterized through a newly defined dimensionless number (χ). The observation of the odd–even effect in hydrophobicity, however, depends on the thiol chain length, and it was only observed on longer-chain (>C8) molecules. The trend in this odd–even effect demonstrates that there are three main transitions in the nature of wetting, hence structure, across <em>n</em>-alkanethiols. From wetting with HD, the role of dispersive components in wetting reveal that the SAMs are dynamic, which we attribute to rotations associated with previously reported evolution in gauche defects and changes in packing density. Therefore, from re-expression of the Young–Dupre equation, we define a new dimensionless number associated with molecular conformations, whose periodicity mirrors the energetics of Goodman’s conformations of <em>n</em>-alkanes in unbound states and associated four- or two-twist turns. Therefore, we infer that the evolution in surface energy is largely due to molecular conformations and associated relaxations of the bound thiolates.</p>
dc.description.comments <p>Reprinted with permission from Chen, Jiahao, Boyce Chang, Stephanie Oyola-Reynoso, Zhengjia Wang, and Martin Thuo. "Quantifying Gauche Defects and Phase Evolution in Self-Assembled Monolayers through Sessile Drops." <em>ACS Omega</em> 2, no. 5 (2017): 2072-2084, doi:<a href="http://dx.doi.org/10.1021/acsomega.7b00355" target="_blank">10.1021/acsomega.7b00355</a>. Copyright 2017 American Chemical Society.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/mse_pubs/240/
dc.identifier.articleid 1245
dc.identifier.contextkey 10544346
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath mse_pubs/240
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/55574
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/mse_pubs/240/2017_Thuo_QuantifyingGauche.pdf|||Fri Jan 14 22:52:21 UTC 2022
dc.source.uri 10.1021/acsomega.7b00355
dc.subject.disciplines Chemical Engineering
dc.subject.disciplines Materials Science and Engineering
dc.subject.disciplines Membrane Science
dc.subject.disciplines Nanotechnology Fabrication
dc.subject.disciplines Polymer and Organic Materials
dc.subject.keywords Conformation
dc.subject.keywords Contact angle
dc.subject.keywords Molecular structure
dc.subject.keywords Phase
dc.subject.keywords Self-assembled monolayers
dc.subject.keywords Surface structure
dc.subject.keywords Wetting
dc.title Quantifying Gauche Defects and Phase Evolution in Self-Assembled Monolayers through Sessile Drops
dc.type article
dc.type.genre article
dspace.entity.type Publication
relation.isAuthorOfPublication fc7bf253-7dbb-48c0-a449-cf5b94c361a7
relation.isOrgUnitOfPublication 25913818-6714-4be5-89a6-f70c8facdf7e
relation.isOrgUnitOfPublication bf9f7e3e-25bd-44d3-b49c-ed98372dee5e
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