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Nano-Scaled Frank-Kasper Supramolecular Lattice and Related Phase Transitions in Precisely Defined Giant Molecules Constructed by Functionalized Nanoparticles

Feng, Xueyan
http://rave.ohiolink.edu/etdc/view?acc_num=akron1499356841029693

Abstract Details

2017, Doctor of Philosophy, University of Akron, Polymer Science.
The research in this dissertation is aimed to develop the giant molecule system, exploring the relationships between the properties of molecules (molecular geometry, molecular functional group, molecular size, etc.) and the formed supramolecular structures by these molecules. The studies are divided into three parts. For the first part, a series of precisely defined ABn type giant molecules were designed and synthesized by connecting one hydrophilic polyhedral oligomeric silsesquioxane nanoparticle (i.e. DPOSS that represents fourteen hydroxyl group functionalized POSS) with different numbers of crystalline hydrophobic POSS nanoparticle(s) (n=1-8) (i.e. BPOSS that represents all isobutyl groups functionalized POSS) via flexible linker(s). With varying the BPOSS number from one to seven, a supramolecular lattice formation sequence ranging from lamella (DPOSS-BPOSS), double gyroids (space group of Ia3 ¯d, DPOSS-BPOSS2), hexagonal cylinder (space group of P6mm, DPOSS-BPOSS3), Frank-Kasper A15 (space group of Pm3 ¯n, DPOSS-BPOSS4, DPOSS-BPOSS5, and DPOSS-BPOSS6), to Frank-Kasper sigma lattice (space group of P42/mnm, DPOSS-BPOSS7) can be observed. The nanostructure formations in this series of ABn type giant molecules are mainly directed by macromolecular geometric shapes. Furthermore, within each spherical motif, the soft spherical core is consisted of hydrophilic DPOSS cages with flexible linkages, while the hydrophobic BPOSS cages form the relative rigid shell and contact with neighbors to provide decreased interfaces among the spherical motifs for constructing final polyhedral motifs in these Frank-Kasper lattices. The crystalline effect of the hydrophobic BPOSS cages would disturb the formation of curved structures. Thus in this set of samples, we have to increase the characterization temperature at elevated temperatures above the melting temperature of BPOSS. In order to explore the relationship between the formed supramolecular structures with temperatures, in the second part, another set of ABn type giant molecules with noncrystalline POSS nanoparticles (i.e. NPOSS) have been synthesized and studied. The phase sequence is similar with the crystalline DPOSS-BPOSSn samples while we found dodecagonal quasicrystal phase (DDQC) and sigma phase occur in single material at different temperatures (both in the sample DPOSS-NPOSS5 and DPOSS-NPOSS6) and demonstrated that the DDQC phase is metastable phase while the Sigma phase is the stable phase. Besides these, in the third part, we also make efforts to develop new synthetic approaches to introduce functional materials into our giant molecule system. With these efforts, it may provide a new insight into the molecular level design and the corresponding formation mechanism to form Frank-Kasper phases, and also provide a platform to design and construct new generations of giant molecules with functional groups for further development of functional materials with desired structures and macroscopic properties.
Stephen Z. D. Cheng (Advisor)
Toshikazu Miyoshi (Committee Chair)
Yu Zhu (Committee Member)
Tianbo Liu (Committee Member)
Chrys Wesdemiotis (Committee Member)
Nanoscience; Polymers

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Citations

  • Feng, X. (2017). Nano-Scaled Frank-Kasper Supramolecular Lattice and Related Phase Transitions in Precisely Defined Giant Molecules Constructed by Functionalized Nanoparticles [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1499356841029693

    APA Style (7th edition)

  • Feng, Xueyan. Nano-Scaled Frank-Kasper Supramolecular Lattice and Related Phase Transitions in Precisely Defined Giant Molecules Constructed by Functionalized Nanoparticles. 2017. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1499356841029693.

    MLA Style (8th edition)

  • Feng, Xueyan. "Nano-Scaled Frank-Kasper Supramolecular Lattice and Related Phase Transitions in Precisely Defined Giant Molecules Constructed by Functionalized Nanoparticles." Doctoral dissertation, University of Akron, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1499356841029693

    Chicago Manual of Style (17th edition)

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