Effects Of Long-range Interaction And Confinement On Polymer Chain Conformation And Morphology

Polymers with ionizable groups are called polyelectrolytes, which can dissociate in polar solvent, leaving charges on polymer chains and releasing counterions in the solution. In addition with such a kind of long-range interaction as the electrostatic interaction between charges, the configurational behaviour of polyelectrolytes in solution, compared to the uncharged polymers, become more complicated. Meanwhile, other properties of polyelectrolyte solution such as viscosity, osmotic pressure and so on will be qualitatively different from those of uncharged polymers as well. Because of these interesting characters and its wide usage in energy, environment, life science, and some other fields, an increasing attention to polyelectrolytes has been gained from 1940s.The confinement is another factor which has dramatically effects on the morphology of polymers. The reason is that the unique phase separation morphologies formed by the block copolymers are related to not only the content of each component and the interaction between the different components, but also the confinement from which the polymer suffers.. The polymer confined in the curved space will also suffer the space's curvature, which would cause different phase behaviour from that in the unlimited flat space.The first chapter is an introduction in which we summed up various theories used in the polyelectrolytes solution research. It is found out that most of the works are focused on one or two particular configuration or the influence of change of the temperature on the electrostatic energy. Considering that the temperature will also change the solvent characteristic which then influence the configurations of polyelectrolyte in solution in terms of the interaction, we propose our work by taking into account the effects both on the electrostatic energy and solvent property of temperature.In the Second chapter, we studied the polyelectrolytes solution with a single chain by Monte Carlo simulation using lattice mode. Our model is built on a hypothesis that every monomer particle has the same cation, and every counter-ion has the same anion. The solution is thus electric neutral. Using Ewald Sum to calculate the electrostatic energy while setting△E*=△E/kBT together withχ=α/kBT(α>0), we can change electrostatic energy and short-range interaction energy at the same time, and learn the property of electrolytes with the change of the temperature. We find out that at a low temperature the chain bone will form a necklace configuration in the case that the chain is long enough. The configuration would change with heating into collapsed globule, random coil, etc. At the very high temperature, the chain bone would form stretched coil.The third chapter is about the TDGL simulation (Time-Dependent Ginzburg-Landau Equation) of phase separation of the diblock copolymer in the closed spherical shell. By using dynamical method based on the TDGL, we have carried on a study of phase behaviour of linear AB diblock copolymer melt system in a series of closed sphere shells with different surface interaction. In the system that has no interaction between surface and chain blocks, we have found out that the radius and the thickness of the spherical shell will mainly influence the behaviour of the phase separation, while the phase separations obey the basic rules of the phase separation theory of block copolymer. In the system that has surface enrichment effect, the radius of the shell have less effect on the phase separation as the influences of the shell thickness and the surface enrichment effect grow. The thicker the shell is, as well as the more effect the surface has on the block, the more different the morphologies perform from which in the neutral surface system. The progress of the phase separation is controlled by both the confinement and the surface enrichment effect. The later affected the morphological behaviour more during the beginning of the separation, and as the phase separation progress carried on, the former showed growing influence. The final morphology is the result of the balance of both factors.