Self-assembly Of Polymer-tethered Inorganic Nanoparticles In Confined Space

Nanocomposites have great potential applications in many fields, such as photoelectric materials, microelectronic devices, bio-sensors, and biomolecular recognition due to their unique properties. The properties and applications of nanocomposites are not only dictated by the size, shape, and chemical composition of the nanoparticles but also dependent on their order, spatial arrangement and orientation. Therefore, the controlled assembly of nanoparticles has great significance in the application of nanotechnology and nanomaterials.In this dissertation, we synthesized polymer-tethered nanoparticles and investigated their self-assembly behaviors in different confined space (e.g., nanopores and interface); we systematically explored the effect of polymer ligand on their self-assembly behavior and the mechanism for the formation of the ordered structures; we also demonstrated the effect of the experimental parameters on spatial arrangement of nanoparticles. Our work may provide theoretical and experimental guidelines for the design and preparation of the nanocomposites with well-ordered strutures in future research. A brief summary of the work in this dissertaion is given below:1. We investigated the self-assembly behavior of anisotropic nanorods in strong two-dimensional confinement under external electric field. The Nanorods successfully overcame strong steric hindrance caused by their special shape and self-assembled into a series of one-dimensional ordered assemblies with special refined structures due to combined effects of polymer chains mobility and the electric field induction. Moreover, we tuned the packing style of nanorods assemblies by varying the direction of external electric field, pore size of the confined channel, and molecular weight of the polymer ligand. Our results revealed that confinement effect played a key role in the self-assembly behavior and packing style of the nanorods.2. We explored the self-assembly behavior of polymer-tethered inorganic nanoparticles at oil/water interface. We fabricated large area(centimeter-sized) free-standing non-closed-packed inorganic nanoparticles monolayers by a modified oil/water evaporation method. We systematically investigated monolayer formation mechanism, which revealed that polymer-tethered nanoparticles acted as surfactant in assembly process. Increasing the concentration of nanoparticles solution remarkably reduced Gibbs free energy of the system and affected the morphology of monolayer. Our results also exhibited change in Surface Plasmon Resonance(SPR) properties of monolayer due to the variation molecular weight of the polymer ligand which influenced interparticle distance. Our work can be used in the preparation of amphiphilic Janus nanoparticles and Surface Enhanced Raman Scattering (SERS) substrates.3. The "soft template" confined effect from supramolecule on the self-assembly behavior of polymer-tethered inorganic nanoparticles was investigated. With supramolecular mediation, shaped nanoparticles could self-assemble into two-dimensional and three-dimensional superlattices. We tuned the lattice constant and layer number of superlattice, by varying the molecular weight of polymer ligand and volume fraction of polymer-tethered nanoparticles and as a result assemblies with different optical and mechanical properties were fabricated. Moreover we also investigated the self-assembly of different sized polymer-tethered nanoparticles into binary superlattices. Through systematic investigation, our results revealed that the assembly behavior and packing style of binary superlattices was mainly dependent on the chain-length of the polymer ligand.In this dissertation, we systematically investigated the self-assembly behaviors of polymer-tethered inorganic nanoparticles in different confinements and a series of ordered inorganic nanocomposites with special refined structures were fabricated. Our work will provide an experimental and theoretical base for further research which will pave the way in understanding of assembly behavior and mechanism of polymer-tethered nanoparticles. In addition, our new facile strategies reported in this dissertation can be used for preparation of nanocomposites which may find applications in photoelectric materials, microelectronic, bio-sensor and biomolecule recognition.