SIMULATION OF SELF-ASSOCIATING POLYMER SYSTEMS - II - RHEOLOGICAL PROPERTIES

Using nonequilibrium molecular dynamics (NEMD), self-associating polym er systems composed of flexible linear telechelic chains with strongly attracting end-groups are studied under the influence of external she aring forces. Interconnection between structural and rheological prope rties of the steady-state system is discussed in detail, including the following aspects: shear-induced intra- and intermolecular structural changes, shear-induced gelation, shear thickening and thinning, thixo tropic effect. We find that a critical factor in the shear behavior of self-associating polymers is the space distribution (topology) of cha in ''bridges'' connecting micellar aggregates. Depending on the topolo gy of the bridges, the system may exhibit shear thickening or shear th inning. Furthermore, the applied external force may cause transitions from continuous (space-filling) associative network, which spans the w hole space, to fibrous textures-threadlike objects which align along t he shear field. These structural reorganizations lead to dramatic chan ges in the shear dependent steady-state viscosity. (C) 1998 American I nstitute of Physics. [S0021-9606(98)51943-5].