Density Functional Theory Study Of Microstructure Of Comblike Copolymer Systems

The relationship between the molecular topology and the assembled microstructure of the copolymer is crucial to its property and application. Comblike copolymers are a class of complex copolymers, and due to the high order of molecular structure and the difficulty in experiments, investigations on the comblike copolymers are scarce to date. In this thesis, density functional theory is applied to study the microstructure of the comblike copolymer systems, in which the effects of volume fraction, chain length, block ratio and solvent quality are considered. This work provides useful information for micelle systhesis and application in the future. The main contents and results are as follows.1. Comblike copolymer melts and solutions are investigated successfully by density functional theory. In melts, the microphase separation structures of the comblike copolymers are changed from cylindrical to lamellar phae with increasing the block length at the two ends of the backbone. In solvents, as the Flory-Huggins parameter between the hydrophobic side chains and the solvent varies, spherical, cylindrical, and vesicular micellles are observed.2. In the comblike copolymer solution, the effects of the grafted points, the side chain and backbone lengths, and the solvent quality on the self-assembly of the comblike copolymers are investigated systematically. Novel morphologies are observed, such as toroidal micelles, cagelike micelles, and 'sphere-in-vesicle' nanostructure. The analysis of the free energy illustrates that the long-range term is vital to the microphase separation, and a phase diagram is mapped out based on our simulation results. The knowledge obtained can provide useful information for future experiments.3. In the comblike copolymer/linear hydrophobic homopolymer solutions, the effects of the composition and the length of the linear homopolymer, as well as the solvent quality, on the cooperative aggregation are studied systematically. The results show that large aggregates of macrophase separation can always be formed with the addition of the homopolymer, where the homopolymer accumulate at the center and the comblike copolymer as the corona with the hydrophobic block distribute at the core/corona interface. This work demonstrates that the structure and size of micelles can be tuned by the controlled addition of appropriate linear homopolymer, leading to a better understanding of the controlled synthesis of micelles with target structure and properties.4. In the comblike copolymer/linear diblock copolymer solutions, the effects of the composition and the length of the linear diblock copolymer, the ratio of the hydrophobic/hydrophilic block, as well as the solvent quality, on the cooperative aggregation are studied systematically. The large aggregates appear easily, where the core inner is composed of the hydrophobic block of the linear diblock copolymer and the outer is composed of the hydrophobic block of the comblike copolymer, and the shell is formed by the two copolymer hydrophilic block. Additionally, the system free energy is analyzed for stability. This provides useful guide for the cooperative micellization investigation.