THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Wednesday, September 7, 2016

2:00 PM
in MRDC Conference Room 3515

will be held the

DISSERTATION DEFENSE

for

Beibei Jiang

"Polymer-Templated Functional Organic-Inorganic Nanocomposites for Lithium Ion Batteries, Capacitors and Ferroelectric Devices"

Committee Members:

Dr. Zhiqun Lin, Advisor, MSE

Dr. Nazanin Bassiri-Gharb, ME

Dr. Meilin Liu, MSE

Dr. Vladimir V. Tsukruk, MSE

Dr. Zhong Lin Wang, MSE

Dr. Gleb Yushin, MSE

Abstract:

Functional hybrid organic-inorganic nanocomposites, formed by integrating two or more materials at the nanoscale with complementary properties, offer the potential to achieve performance, functionality and architecture far beyond those of each constituent. Despite this, we lack a versatile approach to design hybrid nanocomposites with desired functions and properties while having a good control over the size, shape, and architecture of the resulting nanocomposites. In this thesis, we developed a versatile and robust polymer-templated approach for synthesizing organic-inorganic nanocomposites with controllable size, shape, morphology, and functionality. This viable polymer-templated approach enables the in-situ synthesis of inorganic nanocrystals with well-controlled size, shape, and functionality in the presence of some rationally designed polymer template by utilizing the interplay between the functional groups of polymer templates and the inorganic precursors. Two main targeted applications, namely, functional nanocomposites as electrodes for LIBs and as dielectric materials for capacitors guide the polymer-templated strategy when designing the polymer templates and crafting hybrid organic-inorganic nanocomposites. Specifically, the major achievements can be summarized as follows:

First, PVDF-BaTiO3 nanocomposites composed of BaTiO3 nanoparticles with tunable diameter intimately  connected with ferroelectric PVDF was initiated by exploiting both the ability to synthesizing amphiphilic star-like PAA-b-PVDF diblock copolymers as nanoreactors, and the strong coordination interaction between the precursors and hydrophilic PAA blocks. The resulting PVDF-BaTiO3 nanocomposites, with tunable PVDF/BaTiO3 volume ratio, displayed high dielectric constant and low dielectric loss, which is promising for applications in high energy density capacitors. In addition, these PVDF-functionalized BaTiO3 nanoparticles exhibited the ferroelectric tetragonal structure. The ferroelectricity is further substantiated by the Piezoresponse Force Microscopy (PFM) study, which may find applications in nanoscale ferroelectric memory devices.

Second, we extended this star-like diblock copolymer nanoreactor strategy to bottlebrush-like diblock copolymer and crafted ferroelectric PVDF-BaTiO3 nanocomposites composed of ferroelectric BaTiO3 nanorods with tunable diameter, length and aspect ratio stably connected with ferroelectric PVDF.

Third, we crafted ZnFe2O4/carbon nanocomposites comprising small-sized ZnFe2O4 nanoparticles embedded within the continuous carbon network through the pyrolysis of ZnFe2O4 precursors-containing polymer template PS@PAA core@shell nanospheres. The synergy of nanoscopic ZnFe2O4 particles and their hybridization with a continuous conductive carbon network contributes to excellent rate performance and prolonged cycling stability over several hundred cycles.

Finally, we crafted corn-like SnO2 nanocrystals using judiciously designed bottlebrush-like HPC-g-PAA as template and coated the corn-like SnO2 with a thin layer of protective polydopamine (PDA). The synergy of the corn-like nanostructures and the protective PDA coating enabled the excellent electrochemical performance for the PDA-coated corn-like SnO2 electrode, including the superior long-term cycling stability, high Sn→SnO2 reversibility, and excellent rate capability.

The bottom-up crafting of functional hybrid organic-inorganic nanocomposites offers new levels of tailorability to nanostructured materials and promises new opportunities for achieving exquisite control over the surface chemistry and properties of nanocomposites with engineered functionality for diverse applications in energy conversion and storage, catalysis, electronics, nanotechnology, and biotechnology.