Dissipative Particle Dynamics And Theoretical Study Of Complex Block Copolymer Micelle Systems

The amphiphilic block copolymers can self-assemble into micelles in a solvent that is selective for one of their constituents. Recently, a new family of micelles-multicompartment micelles have received great attention due to their unique characters. Multicompartment micelles composed of a water-soluble shell and a segregated hydrophobic core are novel, interesting morphologies for applications in a variety of fields including nanotechnology, controlled release and biotechnology. In this thesis, computer simulation is applied to study the self-assembly behavior of a variety of block copolymer in solution, and a superstrong segregation regime theory model for block copolymer micelle calculations is developed. The main results obtained are:1. The distributions of two hydrophobic agents in a core-shell-corona two-compartment micelle are discussed using dissipative particle dynamics. The simulated results show that when the agents are weakly hydrophobic, their distributions in the micelle are largely affected by the interactions between the agents and the blocks; while for strongly hydrophobic agents, the self-assembly of solubilized species in the micelle is also affected largely by the interactions between the species. The simulation confirms that a core-shell-corona micelle can store two agents within separate nanoscopic compartments simultaneously, and shows that the distributions of the agents can be tailored easily by changing the interactions presented.2. The study of multicompartment micelles formed from star ABC triblock copolymers in water is proposed. The dissipative particle dynamics simulations reveal some new morphologies that had not been observed before, as well as providing a direct visualization of the evolution of wormlike and branched multicompartment micelles that follows the fusion process. Thus, this work provides molecular understanding of multicompartment micelles that is useful for future rational synthesis of novel micelles.3. Dissipative particle dynamics simulations were performed on the morphology and structure of multicompartment micelles and vesicles formed fromπ-shaped ABC block copolymers in water. By varying the chain architecture and the composition of copolymers, a rich variety of morphologies were observed. The simulations show that the hydrophilic block length and the distance between the two grafts play important roles on control of the morphology. Sinceπ-shaped ABC block copolymers can reduce to linear ABC and star ABC block copolymers, they are good model copolymers for studying the self-assembly of complex block copolymers into micelles or vesicles.4. Micellization for various types of H-shaped andπ-shaped ABC block copolymers with same composition in selective solvent is investigated by dissipative particle dynamics simulations. The influences of chain architectures of the block copolymer were studied in a systematic way, and compared with each other. A rich variety of morphologies were observed, such as spherical, wormlike, X-shaped, Y-shaped, ribbon-like, layered rod-like, layered disk-like, as well as network morphologies. The knowledge obtained here as well as the new morphologies identified provide useful information for future rational design and synthesis of novel multicompartment micelles.5. A superstrong segregation regime theory model for core-corona micelles and core-shell-corona micelles is developed. It is shown that as the interaction parameter increases, the shape of the block copolymer micelle changes from spherical to disklike. Quantitative calculations are performed for the AB and ABC block copolymer micelles. The comparisons to the experimental data show the theory model is reliable.