Relation Between Polymer Conformational Structure and Dynamics in Linear and Ring Polyethylene Blends
Cheol Jeong, Jack F. Douglas
Atomistic molecular dynamics simulations of ring-linear polyethylene (PE) blends are employed to understand the relationship between chain conformational structure and the melt dynamics of distinct polymer topologies. As observed in previous studies, we find that the radius of gyration of ring polymers in pure melts scales with molecular mass with a reduced exponent in comparison to linear chains so that ring polymers apparently do not exhibit screened excluded volume interactions as in the case of linear chain polymers. The average molecular shapes of the rings, as quantified from their radius of gyration tensor, are also quite distinct from both swollen or ideal ring polymers under theta point conditions in solution and, moreover, ring polymers in the melt state also have a distinct conformational structure from collapsed chains which are compact and relatively spherical structurally. Rings in the melt state resemble branched polymers with screened binary excluded volume interactions, e.g., percolation clusters. Upon adding the linear chains to a melt of pure rings, we observe a significant swelling of the rings and a corresponding change of molecular shape that is qualitatively similar to dissolving rings in a small molecule good solvent. This swelling arising from altered self-excluded volume interactions translates into a large decrease in ring diffusivity, an effect that becomes even more amplified when the polymer melt is entangled.
and Douglas, J.
Relation Between Polymer Conformational Structure and Dynamics in Linear and Ring Polyethylene Blends, Macromolecular Theory and Simulations
(Accessed August 18, 2022)