Conformational and dynamical properties of ultra-soft colloids in semi-dilute solutions under shear flow

Abstract

We investigate structural and dynamical properties of ultra-soft colloids in dilute and semi-dilute solutions by hybrid mesoscale simulations under linear shear flow. In particular, the influence of functionality on these properties is addressed. Our study combines molecular dynamics simulations for the solute with the multiparticle collision dynamics approach for the coarse-grained solvent. The star polymers exhibit large conformational and orientational changes in shear flow, which we characterize by the radius of gyration tensor and the alignment angle. These quantities show a universal dependence on a concentration- and functionality-dependent Weissenberg number with slight deviations at high shear rates. Moreover, the star polymers display a rotational dynamics with a shear-rate- and concentration-dependent rotation frequency. We attribute the concentration dependence to the screening of hydrodynamic interactions in semi-dilute star-polymer solutions.

A computational and experimental study of the linear and nonlinear response of a star polymer melt with a moderate number of unentangled arms

“…First, simulations using a coupled MD -multiparticle collision dynamics (MPCD) approach have shown that unentangled stars with large f in solutions of varying concentrations, both below and far above the overlap concentration, are less deformed and less aligned than low f star polymers. 57 A simple calculation based on the Rouse model for linear polymers, where the polymers can be viewed as stars with f = 1, 2, by Colby et al 52 reveals that the shear thinning regime develops due to the stretching of the Rouse chains as they are perturbed by the shear flow. Although a Rouse model has been developed for star polymers, 23 it has yet to be employed to study the significance of particle deformation on the rheological response.…”

Momentum conserving Brownian dynamics propagator for complex soft matter fluids

“…However, for highfunctionality ( f = 128), the core of the particle is relatively dense and the deformation of the total star polymer is relatively small. 23 In this work, to keep the description of the test system simple, we therefore assume we can still use the equilibrium interaction as given by Eq. (28).…”

Multi-particle collision dynamics for a coarse-grained model of soft colloids

“…Indeed, this requires the inclusion of the necessary number of (MPCD) solvent particles, making the simulation of large systems quite demanding. Therefore, despite a number of works on the topic that include the study of semidilute solutions, 8,[18][19][20][21][22][23][24] the study of polymer suspensions within this framework has been limited up to now by the very high computational demand of treating the polymers in a detailed, monomer-resolved fashion while in parallel keeping track of the MPCD-solven degrees of freedom. In this respect, a suitable combination of the MPCD efficiency with a simplified model for the polymeric objects could provide a boost to the understanding of the dynamics and of the rheology of semidilute and dense suspensions.…”