Part I: Morphology Transformation of Block Copolymer Micelles containing Quantum Dots in the Corona Part II: The Synthesis and Self-assembly of New Polyferrocenylsilane Block Copolymers

by Meng Zhang

Institution: University of Toronto
Year: 2014
Keywords: block copolymer; micelle; polyferrocenylsilane; quantum dot
Record ID: 2053618
Full text PDF: http://hdl.handle.net/1807/43769


My Ph.D. thesis is presented in two parts. In the first part, I describe the preparation of organic-inorganic hybrid micelles formed from poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) block copolymers and CdSe quantum dots (QDs). Several distinct morphologies were observed including, spheres, finite-sized wormlike networks and clusters of hollow vesicles. A series of experiments were carried out to explore whether these hybrid colloids were thermodynamically stable or formed under kinetic control. Upon addition of 2-propanol (2-PrOH) to a chloroform solution containing a mixture of PS404-b-P4VP76 plus CdSe QDs (2-PrOH is a good solvent for P4VP block and a precipitant for PS block and QDs), uniform spherical micelles formed almost instantly, with a PS core and a thin P4VP corona to which the QDs were attached. Vigorous stirring of this solution for two days led to the formation of three-dimensional wormlike networks consisted of Y-junctions and cylindrical struts, terminated by bulbous spherical end-caps. Even more profound structural changes occurred when the solution was subjected to prolonged magnetic stirring (e.g. 1 month). ii In contrast, manipulating the chemical composition of the initial block copolymer could trigger a spontaneous structural transition from sphere to network of wormlike micelles over 2 h without the need of stirring. The second part of the thesis begins by describing a modular approach for preparing polyferrocenyldimethylsilane (PFS) block copolymers via a Cu-catalyzed alkyne/azide coupling reaction to covalently combine two homopolymers synthesized separately. This strategy opens the door to a broad library of novel functional PFS block copolymers, for example, poly(ferrocenyldimethylsilane-b-N-isopropyl acrylamide) (PFS-b-PNIPAM). In an attempt to expand our understanding of PFS block copolymer self-assembly in polar solvents, I investigated the self-assembly of a new polymer (PFS26-b-PNIPAM105) in alcohol solvents. When the block polymer was dissolved in methanol, ethanol and 2-propanol, it formed long fiber-like micelles with uniform width. I also showed that micelles of this polymer underwent seeded growth in methanol, leading to cylindrical micelles that were nearly mono- dispersed in length.