Lazarenko M. Mechanisms of thermal mobility in molecular crystals, formed by long-chain aliphatic molecules.

The work is devoted to study of thermal motion in the molecular polycrystals, formed by long-chain aliphatic molecules with different chemical defects (vinyl and acidic groups). It was shown, that hydrogen bonds between terminal carboxylic acid groups of long-chain aliphatic molecules rapture in the liquid melt in absence and in the solid phase in presence of double bonds in the chain. The mechanism of reorientation of long-chain aliphatic molecules in orthorhombic rotation-crystalline phase was established. It is determined by topological solitons, corresponding to half-period stretching/compression of zigzag-like aliphatic chain with simultaneous 180o rotation. Topological solitons in long-chain aliphatic molecule crystals originate on terminal methyl groups and on terminal carboxylic acid groups in case of methyl groups absence. It was shown, that in case of stoichiometric barrier (double bond, or dimer ring) the topological solitons reflects from it until their energy becomes sufficient for reorientation and following translation of the chain. When the solitons begin to translatione the molecules from the crystallites, melting of the long-chain aliphatic molecule crystals occurs.