Axial dispersion in dilute solutions of linear and branched polymers in parallel-plate and expansion-contraction microchannels.

The axial dispersion of polymers in microchannels depends on the interplay between microchannel geometry, polymer architecture, and hydrodynamics. Here, we investigate the axial dispersion of linear, comb, and star polymers in parallel-plate and sinusoidal expansion-contraction microchannels at dilute concentrations using multiparticle collision dynamics simulations. The polymers all contain the same number of monomers but differ in their architecture, and we compare two definitions of dilute concentration: the same dilute concentration for all polymers or the same concentration relative to their respective overlap concentrations. The dispersion coefficients measured at a nominal solvent volumetric flow rate are found to depend on both architecture and concentration. We show that the dispersion coefficients collapse as functions of the Péclet number after accounting for confinement effects on the polymer diffusion coefficient and polymer contributions to the flow field, and the dispersion coefficients in the parallel-plate microchannel can be reasonably predicted using a theory that accounts for inhomogeneous distribution of the polymers in the microchannel.