The Microstructures Of Diblock Copolymers Under Intergral And Fractional Confinement Dimensions

Microstructure of block copolymers strongly depends on the confined environment. A rich variety of novel microstructures can be observed through adjusting the confined surfaces, such as their geometric structures and chemical features. These microstructures not only have very important and broad applications, including photonic crystals and high-performance storage device, but also became the fundamental and important issues in polymer physics due to their rich phase behaviors, which has received a continuing attention in recent years. In this dissertation, using a real-space self-consistent field theory we have systematically studied the microstructures and phase behaviors of diblock copolymers under different confinement with integral and fractional confinement dimensions, by adjusting the corresponding phase parameters.For the integeral confinement-dimensions, we took the nanopore confinement as an example to invesitgate the influence of the pore diameter and short-range surface field on the microstructures and phase transition behaviors of diblock copolymers. First, we studied the lamella structures of symmetric diblock copolymers under nanopore confinement with cylindrical symmetries, which are located in the special segregation regions. By varying the pore diameter, we focus on the dependence of the concentric layer thickness on the confinement degree, especially for the "soft" and "hard" lamellae thickness, in which the novel microstructures have also explored. Second, we investigated the short-range surface-induced morphologies of lamella-and cylinder-forming diblock copolymers confined in nanopores. The microstructures and phase behaviors are predicted for the highly asymmetric diblock copolymer with different preferred surface through constructing the two-dimensional phase diagram arranged as the surface field strength and the confinedment degree. In addition, these phase behavior are discussed and analyzed by plotting their free energy curves.For fractional confinement-dimensions, we investigated the microstructures and phase behaviors of lamella-forming diblock copolymers in short-and long-period nanorod arrays, respectively. First, the effects of confinement-confinement and surface field have been studied on the morphologies in the short-period nanorod arrays with the preferential surfaces, where a series of novel microstructures and unique phase transition behaviors have been observed. Second, we studied the strong or weak surface-field-induced microstructure of diblock copolymers in long-period nanorod arrays. Through varying the nanorod diameter, the effects of fractional confinement-dimensions have been discussed on lamella-forming diblock copolymers, and a rich variety of network and mixture structures have been also predicted. Furthermore, the unique phase behaviors have been obtained based on anlayzing the influence of the larger and smaller fraction dimensions and the change of free energy.In short, the microstructures and the corresponding transition behaviors of diblock copolymers have been systematically studied by selecting the unique confinement conditions. Our results were not only compared to the available observations from the simulations and theoretical works, but also predicted for the frist time a series of novel microstructures. We hope our results will be helpful to the material fabrication based on microstructures of block copolymer, and to further understand the phase transition of block copolymers in the confined states, which play a dominate role in the possible experimental and theoretical works.