Coupling between Polymer Conformations and Dynamics Near Amorphous Silica Surfaces: A Direct Insight from Atomistic...

Area of Science:

• Materials Science
• Polymer Physics
• Surface Science

Background:

• Understanding polymer chain dynamics at interfaces is crucial for predicting the properties of nanostructured materials.
• The polymer/solid interphase region's behavior remains a subject of ongoing research and debate.
• Polymeric materials are widely used in commercial applications, necessitating a deeper understanding of their interfacial behavior.

Purpose of the Study:

• To investigate the conformational and dynamical features of polymer chains near amorphous silica surfaces.
• To analyze how surface roughness and chain molecular weight affect polymer dynamics in the interphase region.
• To elucidate the relationship between polymer conformation, structure, and dynamics at the interface.

Main Methods:

• Atomistic simulations were employed to model unentangled and mildly entangled cis-1,4-polybutadiene melts.
• The study accounted for the roughness of the amorphous silica surface.
• Polymer properties were analyzed as a function of distance from the silica slab, chain conformation, and molecular weight.

Main Results:

• Monomeric translational motion parallel to the surface was influenced by the silica slab up to distances related to density fluctuations.
• Intramolecular dynamical heterogeneities were observed in adsorbed polymer chains.
• Chains with longer adsorbed segments ('trains') exhibited slower dynamics compared to those with shorter segments.

Conclusions:

• Surface roughness significantly impacts polymer dynamics in the interphase region, unlike behavior at flat surfaces.
• Configurational entropy, in addition to density-dynamics correlations, plays a key role in the dynamical response of confined polymers.
• The findings provide insights into the complex behavior of polymers at solid interfaces, relevant for material design.