Dynamics of topological solitons in a system of weakly coupled chains

A simple model for a polymer crystal as a system of linear chains with strong intrachain and weak interchain interactions is proposed. The model reveals existence of point structure defects of the vacancy or inclusion type (areas of local extension or contraction of a chain with intact intrachain bonds). The dependence of the dynamics of these defects on the magnitude of interchain interaction was investigated. When the interchain interactions are weak, the defects behave like continual topological solitons with a smooth profile typical of a one-dimensional chain on a periodic substrate. The spectrum of their possible velocities was obtained. An increase in the intensity of interchain interaction leads to the nonexistence of soliton solutions in the form of waves that travel with a constant velocity. The motion of a defect is always accompanied by emission of radiation, which possess some properties that are absent from the one-dimensional Frenkel-Kontorova model.