{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/31687"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/31687","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Synthesis and Characterization of Polylactide-siloxane Block Copolymers as Magnetite Nanoparticle Dispersion Stabilizers","abstract":"Polylactide-siloxane triblock copolymers with pendent carboxylic acid functional groups have been designed and synthesized for study as magnetite nanoparticle dispersion stabilizers. Magnetic nanoparticles are of interest in a variety of biomedical applications, including magnetic field-directed drug delivery and magnetic cell separations. Small magnetite nanoparticles are desirable due to their established biocompatibility and superparamagnetic (lack of magnetic hysteresis) behavior. For in-vivo applications it is important that the magnetic material be coated with biocompatible organic materials to afford dispersion characteristics or to further modify the surfaces of the complexes with biospecific moieties. The synthesis of the triblock copolymers is comprised of three reactions. Difunctional, controlled molecular weight polymethylvinylsiloxane oligomers with either aminopropyl or hydroxybutyl endgroups were prepared in ring-opening redistribution reactions. These oligomers were utilized as macroinitiators for ring-opening L-lactide to provide triblock materials with polymethylvinylsiloxane central blocks and poly(L-lactide) endblocks. The molecular weights of the poly(L-lactide) endblocks were controlled by the mass of L-lactide relative to the moles of macroinitiator. The vinyl groups on the polysiloxane center block were further functionalized with carboxylic acid groups by adding mercaptoacetic acid across the pendent double bonds in an ene-thiol free radical reaction. The carboxylic acid functional siloxane central block was designed to bind to the surfaces of magnetite nanoparticles, while the poly(L-lactide)s served as tailblocks to provide dispersion stabilization in solvents for the poly(L-lactide). The copolymers were complexed with magnetite nanoparticles by electrostatic adsorption of the carboxylates onto the iron oxide surfaces and these complexes were dispersible in dichloromethane. The poly(L-lactide) tailblocks extended into the dichloromethane and provided steric repulsion between the magnetite-polymer complexes.","abstract_html":"Polylactide-siloxane triblock copolymers with pendent carboxylic acid functional groups have been designed and synthesized for study as magnetite nanoparticle dispersion stabilizers. Magnetic nanoparticles are of interest in a variety of biomedical applications, including magnetic field-directed drug delivery and magnetic cell separations. Small magnetite nanoparticles are desirable due to their established biocompatibility and superparamagnetic (lack of magnetic hysteresis) behavior. For in-vivo applications it is important that the magnetic material be coated with biocompatible organic materials to afford dispersion characteristics or to further modify the surfaces of the complexes with biospecific moieties. The synthesis of the triblock copolymers is comprised of three reactions. Difunctional, controlled molecular weight polymethylvinylsiloxane oligomers with either aminopropyl or hydroxybutyl endgroups were prepared in ring-opening redistribution reactions. These oligomers were utilized as macroinitiators for ring-opening L-lactide to provide triblock materials with polymethylvinylsiloxane central blocks and poly(L-lactide) endblocks. The molecular weights of the poly(L-lactide) endblocks were controlled by the mass of L-lactide relative to the moles of macroinitiator. The vinyl groups on the polysiloxane center block were further functionalized with carboxylic acid groups by adding mercaptoacetic acid across the pendent double bonds in an ene-thiol free radical reaction. The carboxylic acid functional siloxane central block was designed to bind to the surfaces of magnetite nanoparticles, while the poly(L-lactide)s served as tailblocks to provide dispersion stabilization in solvents for the poly(L-lactide). The copolymers were complexed with magnetite nanoparticles by electrostatic adsorption of the carboxylates onto the iron oxide surfaces and these complexes were dispersible in dichloromethane. The poly(L-lactide) tailblocks extended into the dichloromethane and provided steric repulsion between the magnetite-polymer complexes.","abstract_has_math":false,"creators":["Ragheb, Ragy"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Chemistry","degree_department":"Chemistry","school":null,"contributors":[],"advisors":[],"committee_chairs":["Riffle, Judy S."],"committee_members":["Esker, Alan R.","McGrath, James E."],"year":2005,"date_issued":"2005-03-29","date_published":"2005-03-29","updated_at":"2026-07-22T22:20:34Z","subjects":["poly(methylvinylsiloxane)","polylactide","magnetite","magnetic","polysiloxane","nanoparticle"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-04122005-102006"],"render_values":[{"text":"etd-04122005-102006","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/31687","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Riffle, Judy S."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Esker, Alan R.","McGrath, James E."]},{"key":"dc:contributor.department","label":"Department","values":["Chemistry"]},{"key":"dc:creator","label":"Author","values":["Ragheb, Ragy"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-03-14T20:33:21Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-03-14T20:33:21Z","2012-04-12"]},{"key":"dc:date.issued","label":"Date","values":["2005-03-29"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["poly(methylvinylsiloxane)","polylactide","magnetite","magnetic","polysiloxane","nanoparticle"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-04122005-102006"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/31687"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Polylactide-siloxane triblock copolymers with pendent carboxylic acid functional groups have been designed and synthesized for study as magnetite nanoparticle dispersion stabilizers. Magnetic nanoparticles are of interest in a variety of biomedical applications, including magnetic field-directed drug delivery and magnetic cell separations. Small magnetite nanoparticles are desirable due to their established biocompatibility and superparamagnetic (lack of magnetic hysteresis) behavior. For in-vivo applications it is important that the magnetic material be coated with biocompatible organic materials to afford dispersion characteristics or to further modify the surfaces of the complexes with biospecific moieties. The synthesis of the triblock copolymers is comprised of three reactions. Difunctional, controlled molecular weight polymethylvinylsiloxane oligomers with either aminopropyl or hydroxybutyl endgroups were prepared in ring-opening redistribution reactions. These oligomers were utilized as macroinitiators for ring-opening L-lactide to provide triblock materials with polymethylvinylsiloxane central blocks and poly(L-lactide) endblocks. The molecular weights of the poly(L-lactide) endblocks were controlled by the mass of L-lactide relative to the moles of macroinitiator. The vinyl groups on the polysiloxane center block were further functionalized with carboxylic acid groups by adding mercaptoacetic acid across the pendent double bonds in an ene-thiol free radical reaction. The carboxylic acid functional siloxane central block was designed to bind to the surfaces of magnetite nanoparticles, while the poly(L-lactide)s served as tailblocks to provide dispersion stabilization in solvents for the poly(L-lactide). The copolymers were complexed with magnetite nanoparticles by electrostatic adsorption of the carboxylates onto the iron oxide surfaces and these complexes were dispersible in dichloromethane. The poly(L-lactide) tailblocks extended into the dichloromethane and provided steric repulsion between the magnetite-polymer complexes."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:title","label":"Title","values":["Synthesis and Characterization of Polylactide-siloxane Block Copolymers as Magnetite Nanoparticle Dispersion Stabilizers"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Riffle, Judy S."],"dc:contributor.committeemember":["Esker, Alan R.","McGrath, James E."],"dc:contributor.department":["Chemistry"],"dc:creator":["Ragheb, Ragy"],"dc:date.accessioned":["2014-03-14T20:33:21Z"],"dc:date.available":["2014-03-14T20:33:21Z","2012-04-12"],"dc:date.issued":["2005-03-29"],"dc:description.abstract":["Polylactide-siloxane triblock copolymers with pendent carboxylic acid functional groups have been designed and synthesized for study as magnetite nanoparticle dispersion stabilizers. Magnetic nanoparticles are of interest in a variety of biomedical applications, including magnetic field-directed drug delivery and magnetic cell separations. Small magnetite nanoparticles are desirable due to their established biocompatibility and superparamagnetic (lack of magnetic hysteresis) behavior. For in-vivo applications it is important that the magnetic material be coated with biocompatible organic materials to afford dispersion characteristics or to further modify the surfaces of the complexes with biospecific moieties. The synthesis of the triblock copolymers is comprised of three reactions. Difunctional, controlled molecular weight polymethylvinylsiloxane oligomers with either aminopropyl or hydroxybutyl endgroups were prepared in ring-opening redistribution reactions. These oligomers were utilized as macroinitiators for ring-opening L-lactide to provide triblock materials with polymethylvinylsiloxane central blocks and poly(L-lactide) endblocks. The molecular weights of the poly(L-lactide) endblocks were controlled by the mass of L-lactide relative to the moles of macroinitiator. The vinyl groups on the polysiloxane center block were further functionalized with carboxylic acid groups by adding mercaptoacetic acid across the pendent double bonds in an ene-thiol free radical reaction. The carboxylic acid functional siloxane central block was designed to bind to the surfaces of magnetite nanoparticles, while the poly(L-lactide)s served as tailblocks to provide dispersion stabilization in solvents for the poly(L-lactide). The copolymers were complexed with magnetite nanoparticles by electrostatic adsorption of the carboxylates onto the iron oxide surfaces and these complexes were dispersible in dichloromethane. The poly(L-lactide) tailblocks extended into the dichloromethane and provided steric repulsion between the magnetite-polymer complexes."],"dc:description.degree":["Master of Science"],"dc:identifier.other":["etd-04122005-102006"],"dc:identifier.uri":["http://hdl.handle.net/10919/31687"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["poly(methylvinylsiloxane)","polylactide","magnetite","magnetic","polysiloxane","nanoparticle"],"dc:title":["Synthesis and Characterization of Polylactide-siloxane Block Copolymers as Magnetite Nanoparticle Dispersion Stabilizers"],"dc:type":["Thesis"],"thesis:degree_discipline":["Chemistry"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:20:34Z"}