Show simple item record

dc.contributor.authorNi, Suolongen_US
dc.date.accessioned2014-03-14T20:20:18Z
dc.date.available2014-03-14T20:20:18Z
dc.date.issued2006-12-12en_US
dc.identifier.otheretd-12142006-105535en_US
dc.identifier.urihttp://hdl.handle.net/10919/30094
dc.description.abstractControlling the surface morphology and degree of crystallinity of poly(L-lactic acid) (PLLA) substrates have recently attracted considerable attention because of their applications in cell adhesion, tissue engineering, and drug delivery. Several techniques have been used to fabricate PLLA substrates, some of which may be invalid because PLLA can degrade during fabrication processes. This dissertation provides the Langmuir-Blodgett (LB) technique as a mechanism for fabricating PLLA substrates at temperatures where PLLA degradation is uncommon. In order to fully understand surface morphologies of PLLA LB-films, studies of Langmuir monolayers at the air/water (A/W) interface using surface pressure-area (Pi-A) isotherm and Brewster angle microscopy (BAM) are vital. PLLA exhibits a first-order liquid expanded to condensed (LE/LC) phase transition with molar mass dependent critical phenomena, the first such observation for a homopolymer Langmuir monolayer. Atomic force microscopy (AFM) images of PLLA LB-films prepared in the LC phase exhibit well-ordered lamellar structures. Molar mass scaling of lamellar dimensions, x-ray reflectivity, and reflection absorption infrared spectroscopy (RAIRS) measurements on PLLA LB-films are consistent with PLLA existing as single molecule 10/3-helices at the A/W interface. Morphologies observed after collapse of the LC monolayer are dependent upon the collapse mechanism and subsequent thermal treatment. For temperatures below the LE/LC critical temperature (Tc), two mechanisms are identified for the formation of three dimensional structures: a buckling and stacking of lamellar monolayers on top of existing lamellae during constant compression rate experiments, and a modified nucleation and growth mechanism during isobaric area relaxation experiments. PLLA LB-films prepared in different Langmuir film phases at temperatures below Tc all contain lamellae with different surface roughnesses and similar helical content. Conventional thermal annealing studies on PLLA LB-films reveal that well-ordered lamellar features are destroyed after annealing the LB-films at bulk crystallization temperature through a melting-recrystallization process, which is confirmed by RAIRS and AFM. Our results may prove useful for studying critical behavior and experimentally testing scaling predictions for two dimensions, the development and testing of theories for crystallization in confined geometries, and separating the roles that roughness and crystallinity play in cell adhesion and spreading on biocompatible polymer surfaces.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartSNI_Dissertation.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.subjectLangmuir-Blodgett filmsen_US
dc.subjectLangmuir monolayersen_US
dc.subjectPoly(L-lactic acid)en_US
dc.subjectthe LE/LC phase transitionen_US
dc.titlePoly(L-Lactic Acid) Langmuir Monolayers at the Air/Water Interface and Langmuir-Blodgett Films on Solid Substrates: Phase Behavior, Surface Morphology, and Crystallinityen_US
dc.typeDissertationen_US
dc.contributor.departmentChemistryen_US
dc.description.degreePh. D.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineChemistryen_US
dc.contributor.committeechairEsker, Alan R.en_US
dc.contributor.committeememberRiffle, Judy S.en_US
dc.contributor.committeememberMarand, Hervé L.en_US
dc.contributor.committeememberCrawford, T. Danielen_US
dc.contributor.committeememberCarlier, Paul R.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-12142006-105535/en_US
dc.date.sdate2006-12-14en_US
dc.date.rdate2010-01-12
dc.date.adate2007-01-12en_US


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record