ИСТИНА

Self-organization of amphiphilic block-copolymers in solutions and melts is a powerful means to prepare nanostructured materials that can be employed in fabrication of microelectronic devices, microreactors and containers for drug and gene delivery. The stable response of the system to the change of external conditions is pure physical in its nature and suggests a robust way of system control in many mechanical, electronic and biological applications. It is known that the architecture of the macromolecules used is crucial in resulting structures as well as the solubility of single parts of the chains. While a simple melt of diblock copolymers provides the well-known spectrum of possible phases with clear transitions among them, comblike macromolecules have more complicated phase diagram due to their advanced topology. Historically the majority of studies were dedicated to the comblike chains with fully flexible parts [1, 2]. Macromolecules with grafted rodlike side groups are potentially of even stronger interest to research in polymer physics due to the variety of possible structures and transitions they can provide both in solutions and melts. One can relate this to the competition between energetic self-assembly into specific aggregates of chains with amphiphilic parts and, on the other hand, the steric constraints induced by liquid-crystalline properties of grafted side groups. These constraints are the result of the asymmetrical stiffness in the system. Here we examine the self-assembly of many comblike macromolecules with stiff insoluble side groups (rods) and flexible soluble backbone in solutions and melts using dissipative particle dynamics technique. In this research many phases and transitions under the change of interaction parameters (or temperature) were achieved for different concentrations of macromolecules. By comparison these results with structures in the system of diblock rod-coil chains putted in the same dilute solution we show that the advanced topology, i.e. binding of side groups in single chain by flexible spacers, results in sphere-like aggregates that were difficult to achieve in rod-coil system where the phase diagram is reach of nematic bundles. This is due to the nematic orientation tendency in rod-coil aggregates which is predominant under the energetic losses. For comblike system the transition from isotropic sphere-like aggregates to nematic bundles generally takes place under the worsening of solution for rods. But for the extreme incompatibility between rods and solution, the reverse transition to spheres occurs due to the huge losses in surface energy for large bundles. Moreover we established that for some values of Flory-Huggins parameter for backbone-solvent interaction in dilute solution a wormlike phase of collapsed islands of rods particularly screened by backbone becomes stable. This can be related to the intrinsic stiffness of the islands which doesn't allow them to mutually interconnect and form general wormlike micelle which can be formed in case of flexible chains. For big enough concentrations a regular flat net of rods under spacers cover was found stable. Interestingly, the net-phase is a subject to transmute into wavy perforated layer and zig-zag layers as the interaction parameters are being changed. These results underscore the importance of studies of comblike polymers with LC properties. 1. Košovan, P., Kuldová, J., Limpouchová, Z., Procházka, K., Zhulina, E. B., & Borisov, O. V. Amphiphilic graft copolymers in selective solvents: molecular dynamics simulations and scaling theory. Macromolecules, 42(17), 6748-6760 (2009) 2. Qi, H., & Zhong, C. Density functional theory studies on the microphase separation of amphiphilic comb copolymers in a selective solvent. The Journal of Physical Chemistry B, 112(35), 10841-10847 (2008)