Disorder-to-Order Transition Of Block Copolymer With Complex Topological Structure

Block copolymer can self-assemble into a variety of ordered structures in nano scales. For those block copolymer with complex topological structure, there would be more microphase structures due to the increasing of monomer species and the topological structure of block copolymer. It is very important in designing the materials with complex structures, therefore, this kind of copolymers has received considerable attention. Compared with the other mean field theory, the self-consistent field theory (SCFT) is the most accurate theory, and fewer hypotheses have been used in it. Therefore, SCFT has become an effective method for the study of the phase behaviors of block copolymer.In this dissertation, based upon a standard Gaussian chain model, we introduced the SCFT in the real space and extended it to study the phase behaviors for the block copolymers with complex topological Structure. The main results are listed as follows:1. The disorder-to-order transition (DOT) of comb block copolymer Am+1(BC)m. By systematically changing the compositions of the three components, we obtained the phase diagrams when the Flory-Huggins interaction parameters between three components are equal and asymmetric, respectively. Besides, we studied the influence of side number on phase behavior when the lengths of block A, B, C are fixed and the total length backbone is fixed, respectively. The interaction parameter of the order-to-disorder transition increases with the increasing of the side chain number and the volume fractions, especially for blocks A and B. We also obtained the phase separation sequence:when interaction parameters are equal, the block C separates from the copolymer first, then block A, and last block B (Câ†'Aâ†'B).2. The disorder-to-order transition (DOT) of coil-comb block copolymer A-(Bm+1Cm). By systematically changing the volume fractions of the three components, we obtained the phase diagrams when the Flory-Huggins interaction parameters between three components are equal and asymmetric, respectively. We found that with the increase of the side chain number and the volume fractions of the blocks, particularly for blocks B and C, the interaction parameter of the order-to-disorder transition increases. When interaction parameters are equal, the microphase separation sequence is Aâ†'Câ†'B. Thus, we can see the topological structure block copolymers largely affect their phase behavior.