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Preparation and Application of Responsive Materials

Zhou, Jinjun
http://rave.ohiolink.edu/etdc/view?acc_num=akron1444324681

Abstract Details

2015, Doctor of Philosophy, University of Akron, Polymer Science.
Synthesis and surface functionalization of different types of semiconductor nanocrystals were extensively explored. High quality spherical nanocrystals (quantum dots, QDs) and rod-shaped nanocrystals (quantum rods, QRs) were prepared using organometallic approaches. To enhance the quantum yield and stability of these nanocrystals, methods for fabricating core-shell structured CdSe/ZnS QDs and core-shell-shell structured nanorods were developed. The nanocrystal surfaces were modified to have different functional groups or to enable their dispersion into aqueous solutions. CdSe/ZnS QDs were made water soluble via ligand exchange with dihydrolipoic acid (DHLA). Dual end-functionalized telechelic poly(N-isopropylacrylamide) (PNIPAM) was synthesized using reversible addition-fragmentation chain-transfer (RAFT) polymerization methodology. One end of the polymer chain was coupled to a fluorescent dye and the other end was covalently coupled to CdSe/ZnS QDs using carbodiimide chemistry. The hybrid nanoparticles exhibit ratiometric changes in fluorescence emission upon temperature cycling between 25 °C and 45 °C due to a fluorescence resonance energy transfer mechanism. As a continuous work to explore the photovoltaic application of semiconductor nanocrystals, a series of low bandgap semi-random copolymers incorporating various ratios of two acceptor units: thienothiadiazole and benzothiadiazole were synthesized using Pd-catalyzed Stille-coupling methodology. The copolymer films exhibited broad and intense absorption spectra, covering the spectral range from 350 nm up to 1240 nm. The optical bandgaps and highest occupied molecular orbital (HOMO) levels of the polymers were calculated from ultraviolet-visible spectroscopy and cyclic voltammetry measurements, respectively. By changing the ratio of the two acceptor monomers, the HOMO levels of the polymers were tuned from -4.42 eV to -5.28 eV and the optical bandgaps were varied from 1.00 eV to 1.14 eV. The results indicated our approach could be applied to the design and preparation of conjugated polymers with specifically desired energy levels and bandgaps for photovoltaic applications. In the final work, amino acid-based poly(ester urea) (PEU) copolymers functionalized with pendant catechol groups that address the need for strongly adhesive yet degradable biomaterials have been developed. Lap-shear tests with aluminum adherends demonstrated that these polymers have lap-shear adhesion strengths of near 1 MPa. An increase in lap-shear adhesive strength to 2.4 MPa was achieved upon the addition of an oxidative cross-linker. The adhesive strength on porcine skin adherends was comparable with commercial fibrin glue. Interfacial energies of the polymeric materials were investigated via contact angle measurements and Johnson-Kendall-Roberts (JKR) technique. The JKR work of adhesion was consistent with contact angle measurements. The chemical and physical properties of PEUs can be controlled using different diols and amino acids, making the polymers good candidates for the development of biological glues for use in clinical applications.
Matthew Becker (Advisor)
Yu Zhu (Committee Chair)
Tianbo Liu (Committee Member)
Abraham Joy (Committee Member)
Xiong Gong (Committee Member)
184 p.
Polymers

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Citations

  • Zhou, J. (2015). Preparation and Application of Responsive Materials [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1444324681

    APA Style (7th edition)

  • Zhou, Jinjun. Preparation and Application of Responsive Materials. 2015. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1444324681.

    MLA Style (8th edition)

  • Zhou, Jinjun. "Preparation and Application of Responsive Materials." Doctoral dissertation, University of Akron, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1444324681

    Chicago Manual of Style (17th edition)

akron1444324681
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This open access ETD is published by University of Akron and OhioLINK.