Synthesis and self-assembly of polymeric hybrid nanomaterials

Abstract

The ability to construct functional polymeric hybrid nanomaterials is critically important for many applications. In this thesis I present the synthesis of amphiphilic polymers of various compositions including insulating coil-coil, semiconducting rod-coil, semiconducting brush-coil, and bioconjugated rod-coil polymers. The self-assembly of these polymers is presented along with methodologies for controlling the organization of nanomaterials and polymers towards the construction of functional hybrid materials with controllable structures and properties. In this thesis, an analysis of the conditions necessary to stabilize the cooperative self-assembly of nanoparticles and amphiphilic block copolymers into a unique cavity-like structure is presented. This work reveals the mechanism behind the formation of the structure and presents experimental and theoretical phase maps that show the conditions required to stabilize this structure for a range of nanoparticle sizes. These self-assembly guidelines provide an essential foundation for the generation of functional composites with predesigned structures and properties. A high-yield click chemistry synthesis of an amphiphilic conjugated block copolymer with systematic block lengths that self-assembles into well-defined nanofibers whose length can be effectively controlled by varying the relative block-lengths is also presented. Furthermore, superstructures of bundled and branched nanofibers with tunable shapes, lengths, and densities were fabricated through hierarchical self-assembly. This work demonstrates that complex superstructures of organic semiconductors can be fabricated via bottom-up self-assembly approach using preformed nanofibers as building blocks. The solution phase self-assembly of an amphiphilic conjugated brush copolymer into an elongated nanoribbon structure is also reported. The subtle effects of hydrogen bonding and pi-pi stacking interactions were investigated and found to be critical in the formation of this unusual structure which has not been reported for amphiphilic conjugated block copolymers and is important because it could offer insight into how internal packing structures affect the electronic properties of the polymer. The synthesis and self-assembly of a bio-conjugated rod-coil block copolymer into distinct nanostructures is also presented. These functional bio-conjugated polymers combine the optoelectronic properties of semiconducting polymers with the bio-recognition properties of DNA and is important because it offers a new approach to forming semiconducting nanostructures with controllable geometries by self-assembly and to interface with biological molecules