Nonequilibrium structural and dynamic behaviors of polar active polymer controlled by head activity

Abstract

Thermodynamic behavior of polymer chains out of equilibrium is a fundamental problem in both polymer physics and biological physics. By using molecular dynamics simulation, we discover a nonequilibrium mechanism that controls the conformation and dynamics of polar active polymer; i.e., head activity commands the overall chain activity, resulting in a re-entrant swelling of active chains and a nonmonotonic variation of the Flory exponent ν. These intriguing phenomena are the result of two competing nonequilibrium effects arising from the head-controlled railway motion of the chain, i.e., dynamic chain rigidity and the curling of chain conformation characterized by the negative bond vector correlation. Moreover, we identify several generic dynamic features of polar active polymers, i.e., linear decay of the end-to-end vector correlation function, polymer-size-dependent crossover from ballistic to diffusive dynamics, and diffusion coefficients sensitive to head activity. A simple dynamics theory is proposed to faithfully explain these interesting dynamic phenomena. These sensitive structural and dynamical responses of active polymer to its head activity provide us a practical way to control active agents with applications in biomedical engineering.