Torsion solitons in linear macromolecules

A phenomenological model for the dynamics of localized (soliton-like) torsion waves in linear macromolecules is considered. It is shown that the anharmonicity of the torsion potential, which characterizes deceleration of rotation of the chain units about a valence bond, can result in the appearance of torsion solitons with a finite supersonic velocity spectrum. The solitons are dynamically stable. They retain their shape in the course of motion, which is not accompanied by phonon radiation. Interaction of solitons is inelastic, Collision of solitons always gives rise to phonon radiation, which becomes especially noticeable near the upper boundary of the velocity spectrum. The existence of torsion solitons should be expected in linear macromolecules that take a three-dimensional helical conformation in the ground state. In macromolecules adopting a flat zigzag conformation, the conditions necessary for the soliton existence are considerably more severe.