Abstract
Star block-copolymers (SBCs) are macromolecules formed by a number of diblock copolymers anchored to a common central core, being the internal monomers solvophilic and the end monomers solvophobic. Recent studies have demonstrated that SBCs constitute self-assembling building blocks with specific softness, functionalization, shape and flexibility. Depending on different physical and chemical parameters, the SBCs can behave as flexible patchy particles. In this paper, we study the rotational dynamics of isolated SBCs using a hybrid mesoscale simulation technique. We compare three different approaches to analyze the dynamics: the laboratory frame, the non-inertial Eckart’s frame and a geometrical approximation relating the conformation of the SBC to the velocity profile of the solvent. We find that the geometrical approach is adequate when dealing with very soft systems, while in the opposite extreme, the dynamics is best explained using the laboratory frame. On the other hand, the Eckart frame is found to be very general and to reproduced well both extreme cases. We also compare the rotational frequency and the kinetic energy with the definitions of the angular momentum and inertia tensor from recent publications.
Highlights
Polymer solutions have an important role from both the fundamental and applied point of views.The addition of a small amount of polymers to a liquid can be use to tune the stability and rheological properties on multiple commercial systems as paints, pharmaceutical products, food and oils.As a consequence of the polymer flexibility, a field flow can provoke large conformational changes, which in turn influence the flow field
We show that star block-copolymer (SBC) display a richer structural and dynamical behavior than athermal star polymers in a shear flow, and they are interesting candidates to tune the viscoelastic properties of complex fluids
We analyzed the rotational dynamics of an isolated star-shaped block copolymer under shear flow for three representative sets of parameters, i.e., a very flexible system (Case 1), an intermediate flexible-rigid system (Case 2) and, a rather rigid system (Case 3)
Summary
Polymer solutions have an important role from both the fundamental and applied point of views.The addition of a small amount of polymers to a liquid can be use to tune the stability and rheological properties on multiple commercial systems as paints, pharmaceutical products, food and oils.As a consequence of the polymer flexibility, a field flow can provoke large conformational changes, which in turn influence the flow field. On top of experimental techniques, the development of simulation methods allowing one to efficiently couple the solvent particles and monomers, a wide spectrum of behaviors has been found regarding the average deformation and the orientation as a function of the shear rate, as well as multiple dynamic responses [3,4,5,6,7,8,9]. The latter encompass stretching and recoil, tumbling, tank-treading, rupture and collapse of polymers and determine the (complex) viscoelastic response of dilute bulk phases
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