Active soft matter, e.g., comprised of filaments or polymers, is a promising new class of materials due to the tight coupling between nonequilibrium fluctuations and conformations [1].  There are various realizations of active polymers. ATP-dependent enzymatic activity-induced mechanical fluctuations drive molecular motion in the cytoplasm of bacteria and eukaryotic cells and affect the properties of DNA molecules. Linear polymers, such as filamentous actin or microtubules of the cell cytoskeleton are propelled by tread-milling and motor proteins. In addition, the dynamics of passive colloidal particles and polymers is enhanced in a bath of propelled filaments [1].

We analyze the conformational, dynamical, and structural properties of self-propelled linear and ring polymers by analytical theory and computer simulations. For the analytical calculations, we consider a Gaussian semiflexible polymer with active sites modeled by an Ornstein-Uhlenbeck process (active Ornstein-Uhlenbeck particle, AOUP), where the active velocity changes in a diffusive manner. In simulations, we employ a bead-spring linear phantom or self-avoiding polymer with active monomers (active Brownian particles, ABPs), where the propulsion direction obeys a random process. Activity leads to a swelling of flexible and, at intermediate activities, shrinkage of semiflexible polymers followed by a reswelling at large activities. Moreover, activity yields a drastic acceleration of both, the center-of-mass and the intramolecular dynamics. Interestingly, accounting for hydrodynamic interactions leads to shrinkage of even flexible active polymers at intermediate activities. Considering suspensions of ABP polymers, we find that connectivity suppresses motility-induced phase separation (MIPS), known for individual ABPs, but leads to cluster formation and collective dynamics. Various results of our studies will be discussed in the presentation.

The predicted novel features by activity are essential for the function of, e.g., biopolymers, and might be exploited in synthetic systems for the rational design of new materials with tailored properties, e.g., dynamical pattern formation and clustering or viscosity modifiers.

[1] S. M. Mousavi, G. Gompper, R. G. Winkler, J. Chem. Phys. 150, 064913 (2019)