Abstract
The dynamics of polymer chains in the polymer/solid interphase region have been a point of debate in recent years. Its understanding is the first step towards the description and the prediction of the properties of a wide family of commercially used polymeric-based nanostructured materials. Here, we present a detailed investigation of the conformational and dynamical features of unentangled and mildly entangled cis-1,4-polybutadiene melts in the vicinity of amorphous silica surface via atomistic simulations. Accounting for the roughness of the surface, we analyze the properties of the polymer chains as a function of their distance from the silica slab, their conformations and the chain molecular weight. Unlike the case of perfectly flat and homogeneous surfaces, the monomeric translational motion parallel to the surface was affected by the presence of the silica slab up to distances comparable with the extension of the density fluctuations. In addition, the intramolecular dynamical heterogeneities in adsorbed chains were revealed by linking the conformations and the structure of the adsorbed chains with their dynamical properties. Strong dynamical heterogeneities within the adsorbed layer are found, with the chains possessing longer sequences of adsorbed segments (“trains”) exhibiting slower dynamics than the adsorbed chains with short ones. Our results suggest that, apart from the density-dynamics correlation, the configurational entropy plays an important role in the dynamical response of the polymers confined between the silica slabs.
Highlights
Hybrid materials containing polymer–solid interfaces have attracted considerable attention in the last few decades due to the large variety of their possible adaptations and a wide span of applications
Dynamics relations in thick films of cis-polybutadiene chains placed between rough amorphous silica slabs in the regime, where the dynamics are not strongly affected by the topological constraints
Concerning the effect of the position of the polymer segment with respect to the substrate on the average structural and dynamical properties, we showed that the lateral translational and orientational dynamics were slowed down near the silica slab and the extension of this effect was in line with the range of the density fluctuations related to the enhanced chain packing near the surface
Summary
Hybrid materials containing polymer–solid interfaces have attracted considerable attention in the last few decades due to the large variety of their possible adaptations and a wide span of applications. Polymer nanocomposites and polymer films are among the most populated types of hybrid polymer materials used for instance, in the tire industry as coatings or in membrane and separation technologies [1,2]. The versatility of these materials comes from the fact that their properties can be tuned by using a broad set of parameters, such as polymer type and its molecular weight; characteristics of the solid interface (e.g., its roughness or shape and mutual interaction with the polymer); dispersion state; and concentration of nanofillers in the case of nanocomposites or film thickness in the case of polymer films. In the case of favorable polymer–solid interactions, the polymer chains adsorb on the surface, forming conformations commonly known as trains, loops and tails. Trains are formed by consecutive adsorbed segments on the surface, the loops consist of segments connecting the trains and the tails are the end sections of adsorbed chains
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