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Preparation of Nitrile Containing Siloxane Triblock COpolymers and Their APplication As Stabilizers For Siloxane Magnetic Fluids

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dc.contributor.authorLi, Chenghongen
dc.contributor.committeechairRiffle, Judy S.en
dc.contributor.committeememberDillard, John G.en
dc.contributor.committeememberWightman, James P.en
dc.contributor.committeememberGibson, Harry W.en
dc.contributor.committeememberMcGrath, James E.en
dc.contributor.departmentChemistryen
dc.date.accessioned2014-03-14T20:51:23Zen
dc.date.adate1996-12-11en
dc.date.available2014-03-14T20:51:23Zen
dc.date.issued1996-12-11en
dc.date.rdate1996-12-11en
dc.date.sdate1998-07-18en
dc.description.abstractNitrile containing siloxane block copolymers were developed as stabilizers for siloxane magnetic fluids. The siloxane magnetic fluids have been recently proposed as internal tamponades for retinal detachment surgery. PDMS-b-PCPMS-b-PDMSs (PDMS = polydimethylsiloxane, PCPMS = poly(3-cyanopropylmethylsiloxane) were successfully prepared through kinetically controlled polymerization of hexamethylcyclotrisiloxane initiated by lithium silanolate endcapped PCPMS macroinitiators. The macroinitiators were prepared by equilibrating mixtures of 3- cyanopropylmethylcyclosiloxanes (DxCN) and dilithium diphenylsilanediolate (DLDPS). DxCNs were synthesized by hydrolysis of 3-cyanopropylmethyldichlorosilane, followed by cyclization and equilibration of the resultant hydrolysates. DLDPS was prepared by deprotonation of diphenylsilanediol with diphenylmethyllithium. It was found that mixtures of DxCN and DLDPS could be equilibrated at 100°C within 5-10 hours. By controlling the DxCN-to-DLDPS ratio, macroinitiators of different molecular weights could be obtained. The major cyclics in the macroinitiator equilibrate are tetramer (8.6 ± 0.7 wt%), pentamer (6.3 ± 0.8 wt%) and hexamer (2.1 ± 0.5 wt%). 2.5k-2.5k-2.5k, 4k-4k-4k, and 8k-8k-8k triblock copolymers were prepared and characterized. These triblock copolymers are transparent, microphase separated and highly viscous liquids. It was found that these triblock copolymers can stabilize nanometer gamma-Fe₂O₃ and cobalt particles in octamethylcyclotetrasiloxane or hexane. Hence PDMS-b-PCPMS -b-PDMSs represent a class of promising steric stabilizers for silicone magnetic fluids.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-383911142975720en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-383911142975720/en
dc.identifier.urihttp://hdl.handle.net/10919/36655en
dc.publisherVirginia Techen
dc.relation.haspartetd.pdfen
dc.relation.haspartETD17.PDFen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectpolysiloxanesen
dc.subjectblock copolymersen
dc.subjectstabilizersen
dc.titlePreparation of Nitrile Containing Siloxane Triblock COpolymers and Their APplication As Stabilizers For Siloxane Magnetic Fluidsen
dc.typeThesisen
thesis.degree.disciplineChemistryen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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