Georgia Institute of Technology Materials Science and Engineering

Committee Members:

Prof. Zhiqun Lin, Advisor, MSE

Prof. Seung Soon Jang, MSE

Prof. Zhitao Kang, GTRI/MSE

Prof. Vladimir Tsukruk, MSE

Prof. Xing Xie, CEE

"Polymer-Ligated Nanocrystals with Tunable Dimensions, Compositions, and Architectures "

Abstract:

 The ability to produce monodisperse nanocrystals with stable and tunable surface chemistry is of key importance to render investigation into their size- and shape-dependent physical properties and thus an array of applications including electronics, photonics, catalysis, sensors, energy storage, information technology, bionanotechnology, etc. In this context, nonlinear block copolymer nanoreactor has emerged as a general and robust route to synthesis of a gallery of nanocrystals with precisely controlled sizes, shapes, compositions, and surface chemistry.  

In this thesis, I will capitalize on a set of rationally designed star-like and bottlebrush-like block copolymer to template the growth of a host of functional 0D and 1D nanocrystals with controlled dimensions, compositions, and architectures, and scrutinize the dependence of physical properties and energy-related applications on their size, shape, and surface chemistry. First, a series of star-like and bottlebrush-like block copolymers will be synthesized via sequential atom transfer radical polymerization (ATRP) of tert-butyl acrylate (tBA) and styrene from star-like and bottlebrush-like macroinitiators, respectively. The inner hydrophobic poly(tert-butyl acrylate) (PtBA) blocks will then be converted into hydrophilic poly(acrylic acid) (PAA), which strongly coordinate with the metal moieties of precursors of targeted nanocrystals, leading to the nucleation and growth of nanocrystals confined within the space occupied by the PAA blocks. As a result, the size and shape of nanocrystals can be readily controlled by the molecular weight of PAA blocks (i.e., diameter of nanoparticles and nanorods) and polymer backbone (i.e., length of nanorods). Moreover, the outer PS blocks, originally covalently linked to the inner PAA blocks, form a layer of permanently anchored ligands on the nanocrystal surface to enable stable surface chemistry. 

After the successful synthesis of star-like and bottlebrush-like PAA-b-PS templates, a diversity of 0D and 1D functional nanocrystals will be crafted for investigation into their physical properties and applications. For example, a ternary nanocomposite consisting of antibacterial silver NPs, photocatalytic titania oxide NPs, and upconverting NPs are prepared, manifesting a greatly enhanced biocidal performance. Moreover, spinel oxides (e.g., cobalt and nickel ferrite) NPs and NRs will be crafted to interrogate the effects of their size and shape on magnetic and electrocatalytic as well as photothermal properties. Furthermore, the effect of surface chemistry on the solubility (water-soluble vs. organic solvent-soluble) and stability of nanocrystals will be explored by varying the composition and number of outer polymer blocks. In addition, by adjusting the amount of precursors loaded in the star-like and bottlebrush-like block copolymer templates, nanoclusters (instead of nanocrystals) could be yielded, opening up a new avenue of applications in catalysis, plasmonics, etc.