RU Seminar - 23.06.21 Michael Bley "Controlling the solvent quality by time: Enhanced size scaling through persistent polymer chain growth"

Polymer physics provides universal scaling laws, which allow describing macromolecular conformations in equilibrium and which are fundamental for characterizing structure, dynamics, and the functionality of soft matter and materials science. Studying diffusion-influenced nonequilibrium chain-growth polymerization revealed to us that scaling laws change qualitatively dependent on the reaction conditions. Growing polymers exhibit a surprising self-avoiding walk behaviour in poor and in θ-solvents. The analysis of our results from monomer-resolved reaction-diffusion computer simulations showed that these observations result from a complex competition of time scales. Nonequilibrium monomer density depletion correlations around the active polymerization site resulting from fast reaction in the diffusion-controlled limit lead to a locally directed and self-avoiding growth behaviour. This enhanced scaling requires that also the chain (Rouse) relaxation time is larger than the competing polymerization reaction time scale. These intrinsic nonequilibrium mechanisms are boosted by fast and persistent reaction-driven diffusion of the active site with analogies to the pseudo-chemotactic behaviour of active Brownian particles. Varying monomer densities and reaction speed yields a rich state diagram of scaling exponents for all types of solvent qualities. Controlling the solvent quality through the competing time scales has implications for processes of time-controlled structure formation in polymer processing and colloidal self-assembly, as in, e.g., reactive self-assembly, photo-crosslinking, and 3D printing.