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A new multi-step self-assembly route to polymer-semiconducting nanoparticle photonic structures is described. The multi-step self-assembly strategy targets complex hierarchical structures in which organization of cadmium sulfide (CdS) nanoparticles on progressively longer length scales is introduced via a series of three self-assembly steps. each involving building blocks of increasing structural complexity. Each self assembly step can be described as follows: 1) SA1: self-assembly of PS-b-PAA to form block ionomer reverse micelles, followed by synthesis of a single CdS semiconducting nanoparticle in each core, forming the hybrid building blocks PS-CdS: 2) SA2: self-assembly of blends of PS-CdS and PS-b-PAA stabilizing chains in DMF/water mixtures by addition of water to form spherical nanoparticle assemblies, termed large compound micelles (LCMs); 3) SA3: self-assembly of LCMs into ordered close packed arrays by slow water evaporation. The kinetic freezing of building blocks at each stage offers the potential for unique control of nanoparticle self-assembly step since each step is "locked in", allowing structural features determined by the subsequent step to be independently tuned through a new set of experimental variables. Chapter 2 and 3 of this thesis investigate aspects of size and polydispersity control of spherical nanoparticle assemblies in the SA2 self-assembly step. Chapter 4 demonstrates that LCMs can be further assembled (SA3 step) to form three-dimensional hierarchical arrays. |
