**Effectiveness of DPD Simulations to Predict the Dynamics of Polymer
Chains in Solutions at Equilibrium and Steady Shear Flows**

P Kumar and S Jana and H Shyam and IS Dalal, MACROMOLECULAR THEORY AND SIMULATIONS, 32, 2300045 (2023).

DOI: 10.1002/mats.202300045

The suitability of dissipative particle dynamics simulations is investigated to predict the dynamics of polymer chains in dilute polymer solutions. The authors find that the predictions depend on the value of the repulsive parameter for bead-bead pairwise interactions used in the DPD simulations (a(ij)). For all systems, the chain sizes and the relaxation time spectrum are analyzed. For a(ij) = 0, theta solvent behaviour is obtained, whereas the dynamics at equilibrium agrees well with the predictions of the Zimm model. For higher values of aij, the static properties of the chain show good solvent behaviour. However, the scaling laws for the chain dynamics at equilibrium show wide variations, with consistent results obtained only at an intermediate value of a(ij) = 25. At higher values of the repulsive parameter (a(ij) >= 25), the simulations are also able to predict the abrupt cut-off in the relaxation spectrum, which has been observed earlier in experiments of dilute solutions. To verify further, the chain dynamics in shear flow using DPD simulations is studied. Specifically, the variation of the chain is analysed stretch and end-over-end tumbling with shear rates. Overall, the trends obtained from DPD simulations agree well with those observed in earlier BD simulations.

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