Self-assembling Kinetics Of A Diblock Copolymer Melt In Confined Geometries

The self-assembly of block copolymer has attracted much interest of researchers due to the formation of rich microstructures and potential industrial applications of these structures. For the simplest AB diblock copolymers can occur microphase separation and self-assemble to form various periodic structures such as lamellae, a bicontinuous network structure gyroid, hexagonally packed cylinders and body-centered-cubic spherical phases in the bulk. But we know that the formation of these structures has many defects unable to meet the actual demand of industrial applications. The geometrical confinement is usually one of the effective methods for obtaing long range ordered microstructures. At the same time, the introduction of geometrical confinement changes the original structure symmetry, curvature surface and interaction, and obtaing novel structures that unable to get in the bulk. In this thesis, we systematically investigate the self-assembling kinetics of a diblock copolymer melts confined in three-dimensional confinement using Cell Dynamics Simulation which is based on the Time-Dependent Ginzburg-Landau Theory. The following is the specific works done:Firstly, we calculated the natural period of lamellae and sphere phase structures in the bulk, which is crucial for the further studies of diblock copolymers confined in the geometric space. Next, the main part of our work, we systematically investigate the self-assembling kinetics of a diblock copolymer melt confined in cylindrical nanopores. The results indicate that for a sphere-forming copolymer, a variety of new phase structures can be formed under cylindrical nanopores. A series of phase structures formed are determined by the ratio between the period L0 of spheres in the bulk and the pore diameter D, as well as the interaction of polymer-wall. When the pore wall preferential for the majority block, as the pore wall increases, the following sequence of new structures:a single straight cylinder, stacked disks, single helix, double helix, triple helix, titled toroids, dengerate structures, alternating single helix and a string of spheres, alternating four helix and a string of spheres, alternating four helix and a string spheres, alternating four helix and a single straight cylinder, alternating toroids and a string spheres, single helix and cylinder, double helix and cylinder, four straight cylinders, nine straight cylinders, etc. While the pore wall preferential for the minority, we find that the sequence of structures is almost unchanged. We analysed the correlation length of single helix and the chirality of left-hand/right-hand helix, and found that the ratio is about 1:1. Furthermore, we analysed the truly long-range ordered morphologies of single cylinder and stacked disks in macroscopically long nanopores when the pore size is located in the corresponding equilibrium region of two phases. Whereas the free-energy difference between neighboring phases formed in larger nanopores, such as stacked disks and single helix, and single helix and double helix, becomes smaller, or even there are two degenerate states, e.g. left-handed and right-handed helical morphologies, coexisting morphologies composed of two or more phases are observed including coexisting stacked disks and single helix, left-handed and right-handed helices, single and double helical morphologies. A rich variety of defects are present at the interface of two different morphologies, and their formation is explained in the part of physical mechanisms.Finally, we simply study the self-assemble morphologies of diblock copolymers confined in ellipsoidal nanopores. The results show a series of phase structures, such as a single ellipsoidal ball, stacked rings, single helix and double helix, etc.