Molecular thin films and their role in controlling interface properties

dc.contributor.authorIarikov, Dmitrien
dc.contributor.committeechairDucker, William A.en
dc.contributor.committeememberDavis, Richey M.en
dc.contributor.committeememberMartin, Stephen Michaelen
dc.contributor.committeememberBehkam, Baharehen
dc.contributor.departmentChemical Engineeringen
dc.date.accessioned2015-04-09T06:00:11Zen
dc.date.available2015-04-09T06:00:11Zen
dc.date.issued2013-10-15en
dc.description.abstractIn the first part of this study, frictional and normal forces in aqueous solutions were measured between a glass particle and oligopeptide films grafted from a glass plate. Homopeptide molecules consisting of 11 monomers of different amino acids were each "grafted from" an oxidized silicon wafer using microwave-assisted solid phase peptide synthesis. Oligopeptides increased the magnitude of friction compared to a bare hydrophilic silicon wafer. Friction was a strong function of the nature of the monomer unit and was lower for hydrophilic films. There was a strong adhesion and therefore friction between surfaces of opposite charges. Changes in adhesion and friction depended on the hydrophobicity and electrostatic forces: hydrophobic films and oppositely charged films produced high friction, whereas hydrophilic and like-charges produced low friction. Friction was lower in phosphate buffered saline than in pure water due to the screening of the double layer attraction for oppositely charged surfaces and additional lubrication by hydrated salt ions. We also investigated antimicrobial action of poly (allyl amine) (PA) when covalently bonded to glass. Glass surfaces were prepared by a two-step procedure where the glass was first functionalized with epoxide groups using 3-glycidoxypropyltrimethoxy silane (GOPTS) and then exposed to PA to bind via reaction of a fraction of its amine groups. Antibacterial properties of these coatings were evaluated by spraying aqueous suspensions of bacteria on the functionalized glass slides, incubating them under agar, and counting the number of surviving cell colonies. The PA film displayed strong anti-microbial activity against both Gram-positive and Gram-negative bacteria. Films that were prepared by allowing the PA to self assemble onto the solid via electrostatic interactions were ineffective antimicrobials. Such films had an insufficient positive charge and did not extend far from the solid. Thus we found that antimicrobial activity was correlated with a combination of the ability of the polymer chain to extend into solution and a positive surface potential.en
dc.description.degreePh. D.en
dc.format.mediumETDen
dc.identifier.othervt_gsexam:1640en
dc.identifier.urihttp://hdl.handle.net/10919/51675en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectantimicrobial surfacesen
dc.subjectpoly(allylamine)en
dc.subjectlateral force microscopyen
dc.subjectatomic force microscopyen
dc.subjectpeptide synthesisen
dc.titleMolecular thin films and their role in controlling interface propertiesen
dc.typeDissertationen
thesis.degree.disciplineChemical Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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