Show simple item record

dc.contributor.authorNeyman, Patrick J.en_US
dc.date.accessioned2002-05-29en_US
dc.date.accessioned2014-03-14T20:38:19Z
dc.date.available2014-03-14T20:38:19Z
dc.date.issued2002-04-30en_US
dc.identifier.otheretd-05232002-161046en_US
dc.identifier.urihttp://hdl.handle.net/10919/33137
dc.description.abstractIonically self-assembled monolayer (ISAM) films are typically an assemblage of oppositely charged polymers built layer by layer through coulombic attraction utilizing an environmentally friendly process to form ordered structures that are uniform, molecularly smooth, and physically robust. ISAM films have been shown to be capable of the noncentrosymmetric order requisite for a second-order nonlinear optical response. However, films fabricated with a nonlinear optical (NLO) polymer result in significant cancellation of the chromophore orientations. This cancellation occurs by two mechanisms: competitive orientation due to the ionic bonding of the polymer chromophore with the subsequent polycation layer, and random orientation of the chromophores within the bulk of each polyanion layer. A reduction in film thickness accompanied by an increase in net polar ordering is one possible avenue to obtain the second-order nonlinear optical susceptibility chi(2) necessary for electro-optic devices. In this thesis, we will discuss the structural characteristics of ISAM films and explore three novel approaches to obtain the desired characteristics for nonlinear optical response. One approach involves the variation of solution parameters of several different cationic polymers separately from the polyanion solution in order to reduce the competitive chromophore orientation at the layer interfaces and to reduce the thickness of the inactive polycation layer. We have found that the complexity of ISAM films does not allow large chi(2) values in polyion-based films, and that the selection of the polymer cation is vital to achieve second harmonic generation (SHG) at all. The second approach involves the incorporation of dianionic molecules into ISAM films in order to eliminate both competitive chromophore orientation and random chromophore orientation inherent with polymer chromophores. We have also studied the effects of complexing dianionic chromophores with beta-cyclodextrin in order to increase solubility and improve chromophore orientation. This approach fails because the outermost monolayer of dianionic chromophore is only tethered to the preceding polycation layer by a single ionic bond for each molecule, so each chromophore can by dissociated during the following immersion into the cation solution. Finally, we have introduced a novel approach of hybrid covalent / ionic self-assembly which overcomes these disadvantages and yields a substantial increase in chi(2) due to the chromophore being locked in place to the preceding polycation layer by a covalent bond. The films fabricated in this manner yield a chi(2) that rival any polymer-polymer films despite the very low first-order molecular hyperpolarizability beta of the incorporated monomer. This suggests that incorporation of high beta molecules may result in significant improvement of chi(2), holding high promise for the hybrid covalent / ionic self-assembly technique.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartPat_Neyman_Master_Thesis.pdfen_US
dc.relation.haspartPat_Neyman_Vita.pdfen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectsecond harmonic generationen_US
dc.subjectisamen_US
dc.subjectpolymeren_US
dc.subjectionically self assembled monolayersen_US
dc.subjectnanotechnologyen_US
dc.subjectthin filmen_US
dc.subjectchromophoreen_US
dc.subjectnonlinear opticsen_US
dc.titleNonlinear Optical Properties and Structural Characteristics of Ionically Self-Assembled Nanoscale Polymer Films Influenced by Ionic Concentration and Incorporation of Monomer Chromophoresen_US
dc.typeThesisen_US
dc.contributor.departmentMaterials Science and Engineeringen_US
dc.description.degreeMSen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
dc.contributor.committeechairHeflin, James R.en_US
dc.contributor.committeememberMarand, Hervé L.en_US
dc.contributor.committeememberGuido, Louis J.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05232002-161046en_US
dc.date.sdate2002-05-23en_US
dc.date.rdate2003-05-29


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record