Bio-inspired Design and Self-Assembly of Nucleobase- and Ion-Containing Polymers

dc.contributor.authorZhang, Kerenen
dc.contributor.committeechairLong, Timothy E.en
dc.contributor.committeememberMoore, Robert Bowenen
dc.contributor.committeememberGrove, Tijanaen
dc.contributor.committeememberTurner, S. Richarden
dc.contributor.departmentChemistryen
dc.date.accessioned2017-01-06T07:00:16Zen
dc.date.available2017-01-06T07:00:16Zen
dc.date.issued2016-06-24en
dc.description.abstractBio-inspired monomers functionalized with nucleobase or ionic group allowed synthesis of supramolecular polymers using free radical polymerization and controlled radical polymerization techniques. Comprehensive investigations for the structure-property-morphology relationships of these supramolecular polymers elucidated the effect of noncovalent interactions on polymer physical properties and self-assembly behaviors. Reverse addition-fragmentation chain transfer (RAFT) polymerization afforded acrylic ABC and ABA triblock copolymers with nucleobase-functionalized external blocks and a low-Tg central block. The hard-soft-hard triblock polymer architecture drove microphase-separation into a physically crosslinked hard phase in a low Tg matrix. Hydrogen bonding in the hard phase enhanced the mechanical strength and maintained processability of microphase-separated copolymers for thermoplastics and elastomers. A thermodynamically favored one-to-one stoichiometry of adenine and thymine yielded the optimal thermomechanical performance. Intermolecular hydrogen bonding of two thymine units and one adenine unit allowed the formation of base triplets and directed self-assembly of ABC triblock copolymers into remarkably well-defined lamellae with long-range ordering. Acetyl protected cytosine and guanine-containing random copolymers exhibited tunable cohesive strength and peel strength as pressure sensitive adhesives. Post-functionalization converted unprotected cytosine pendent groups in acrylic random copolymers to ureido-cytosine units that formed quadruple self-hydrogen bonding. Ureido-cytosine containing random copolymers self-assembled into nano-fibrillar hard domains in a soft acrylic matrix, and exhibited enhanced cohesive strength, wide service temperature window, and low moisture uptake as soft adhesives. A library of styrenic DABCO salt-containing monomers allowed the synthesis of random ionomers with two quaternized nitrogen cations on each ionic pendant group. Thermomechanical, morphological, and rheological analyses revealed that doubly-charged DABCO salts formed stronger ionic association and promoted more well-defined microphase-separation compared to singly-charged analogs with the same charge density. Bulkier counterions led to enhanced thermal stability, increased phase-mixing, and reduced water uptake for DABCO salt-containing copolymers, while alkyl substituent lengths only significantly affected water uptake of DABCO salt-containing copolymers. Step growth polymerization of plant oil-based AB monomer and diamines enabled the synthesis of unprecedented isocyanate-free poly(amide hydroxyurethane)s, the first examples of film-forming, linear isocyanate-free polyurethanes with mechanical integrity and processability. Successful electrospinning of segmented PAHUs afforded randomly orientated, semicrystalline fibers that formed stretchable, free-standing fiber mats with superior cell adhesion and biocompatibility.en
dc.description.degreePh. D.en
dc.format.mediumETDen
dc.identifier.othervt_gsexam:8080en
dc.identifier.urihttp://hdl.handle.net/10919/73986en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectnoncovalent interactionen
dc.subjecthydrogen bondingen
dc.subjectionic interactionen
dc.subjectnucleobaseen
dc.subjectDABCO salten
dc.subjectself-assemblyen
dc.subjectmicrophase-separationen
dc.subjectnon-isocyanate polyurethaneen
dc.titleBio-inspired Design and Self-Assembly of Nucleobase- and Ion-Containing Polymersen
dc.typeDissertationen
thesis.degree.disciplineChemistryen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en
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