2014: Associate Prof. Victor Ivanov (chair of polymers and crystals) defended his Dr. Sciences thesis on "Computer Modeling of Phase Equilibrium in the Systems of Semiflexible Polymers and Crystals"

In April 2014, Associate Prof. Victor Ivanov (chair of polymers and crystals) defended his Dr. Sciences thesis on Computer Modeling of Phase Equilibrium in the Systems of Semiflexible Polymers and Crystals."

In his Dr.Sci. thesis V.A.Ivanov has performed a comprehensive study of the phase behavior of various systems of semiflexible macromolecules by means of computer simulations and analytical theory. Solutions of semiflexible macromolecules of different concentrations (from extremely dilute, where the properties of single macromolecules we studied, up to concentrated solution) in bulk and under spatial constraints (near flat surfaces and inside thin films) have been studied. Phase diagrams (or diagrams of state for small systems) have been calculated. Main method of research was mesoscopic computer simulation with emphasis on lattice models of polymer systems and different Monte Carlo (MC) algorithms, including extended ensemble techniques, combined with algorithms for constructing the density of states function.

The intramolecular orientation and spatial ordering of segments in a single chain in bulk and in a single chain grafted at one end to a flat adsorbing surface have been studied in detail, and the corresponding diagram of states for a single chain of finite length has been constructed. In semidilute and concentrated solutions of semiflexible chains the phenomenon of nematic liquid crystalline (LC) ordering has been investigated, and the methods of calculation of the phase diagram of these solution in computer simulations have been developed. The effects of the finite size of the system and the phase behavior in the presence of spatial constraints (for example, a thin flat film) have been discussed. The phase diagrams of the solutions of semiflexible polymers in bulk and in a thin film have been calculated.

The important role of intra-chain stiffness has been confirmed, which leads to a complex phase behavior. It has been shown, that the stiffness of polymer chains which is measured in experiments is due to not only pure intrachain rigidity, but also strongly depends on the environment (concentration of the solution, presence of spacial constraints, etc.). Within the framwork of approach of conformation-dependent sequence design of AB-copolymers it was shown, that the conformational behavior of protein-like AB-copolymers differs significantly from the behavior of random and regular multiblock AB-copolymers. It was also shown, that the conformational behavior of flexible-semiflexible copolymer can be strongly changed by changing the ratio of the lengths of semiflexible and flexible blocks. A primary sequence of AB-copolymer was proposed, which reduces the aggregation number of micelles in a solvent which is selective to blocks A and B and accelerates adsorption of macromolecules on the surfaces in comparison with the diblock copolymer of the same composition.