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Synthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphiles

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dc.contributor.authorLiu, Yangen
dc.contributor.committeechairEsker, Alan R.en
dc.contributor.committeememberGandour, Richard D.en
dc.contributor.committeememberMorris, John R.en
dc.contributor.departmentChemistryen
dc.date.accessioned2017-04-04T19:50:20Zen
dc.date.adate2011-01-05en
dc.date.available2017-04-04T19:50:20Zen
dc.date.issued2010-12-06en
dc.date.rdate2016-10-07en
dc.date.sdate2010-12-17en
dc.description.abstractPolyhedral oligomeric silsesquioxanes (POSS) have attracted substantial academic interest for many years as hybrid materials and nanofillers for controlling thermal and mechanical properties, and for providing thermal and chemical resistance while retaining ease of processing. A natural extension of these studies has been working on POSS-based amphiphiles and thin film coatings. Studies at the air/water (A/W) interface have shown that trisilanol-POSS derivatives are amphiphilic and form uniform Langmuir films, whereas closed-cage POSS derivatives are hydrophobic and aggregate. In this study, two novel POSS derivatives were synthesized from PSS-(3-hydroxypropyl)-heptaisobutyl substituted (POSS-OH) and completely characterized. Weisocyanate reacted with POSS-OH, and a POSS-based triester (POSS-triester) was obtained. Trifluoroacidolysis of the POSS-triester at room temperature afforded the corresponding triacid (POSS-triacid). Purified POSS-OH, POSS-triester, and POSS-triacid were studied by using surface pressure - area per molecule (? -A) isotherms as well as Brewster angle microscopy (BAM) at the air/water (A/W) interface. Compared with previous work on trisilanol-POSS derivatives, the results indicated that POSS-triester was surface active and formed a liquid-expanded (LE) monolayer. In contrast, POSS-triacid monolayers were more condensed (LC) and were not dramatically affected by changes in pH. Results for the lift-off areas (Alift-off), limiting areas (A0), collapse areas (Ac), and collapse pressures (? c) of POSS-OH, POSS-triester, and POSS-triacid were compared to trisilanolisobutyl-POSS (TiBP) and were interpreted in terms of possible molecular conformations. Whereas, TiBP has been hypothesized to exist in a vertex-on conformation, POSS-OH and POSS-triacid packing at the A/W interface was consistent with face-on conformations. For POSS-triester, the isotherm was consistent with a vertex-on conformation at low ? , but a face-on conformation at high ? .en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-12172010-220808en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-12172010-220808/en
dc.identifier.urihttp://hdl.handle.net/10919/76922en
dc.language.isoen_USen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectPOSSen
dc.subjectair/water (A/W) interfaceen
dc.subjectBrewster angle microscopy (BAM)en
dc.subjectΠ-A isothermsen
dc.subjectLangmuir filmsen
dc.titleSynthesis and Characterization of Polyhedral Oligomeric Silsesquioxane (POSS) Based Amphiphilesen
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineChemistryen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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