Atomistic Descriptions of thecis-1,4-Polybutadiene/Silica Interfaces

Abstract

Since the early 1940s, silica has been increasingly used in tire compounds as a complement to carbon blacks. The use of silica offers substantial benefits in tires, such as a low rolling resistance and a better grip on wet and icy roads. Nevertheless, coupling agents must be used to enable the mixing with rubber. The understanding of the action of silica in the reinforcement process and the role of the coupling agents at the molecular level requires the investigation of the interfacial region of the silica surface interacting with polymer chains. We report here detailed atomistic simulations of the interfacial region between different silica surfaces and cis-1,4-polybutadiene polymer chains. We describe the interfacial regions in terms of density and the radius of gyration component profiles along the normal to the substrate. We investigate how the nature of the silica surface, the surface density of silanols, and the surface coverage of grafted polymer chains and grafted OCTEO impact the molecular arrangements of the interfacial zone and the local properties of polymer chains.

Conformations and Dynamics of Polymer Chains in Cis and Trans Polybutadiene/Silica Nanocomposites through Atomistic Simulations: From the Unentangled to the Entangled Regime

“…In a series of two papers, Pavlov and Khalatur , studied the mechanical and volumetric properties of silica-filled cross-linked PB nanocomposites. More recently, Kempfer et al utilized atomistic molecular dynamics simulations to study the effect of surface modification on the structural properties, such as density and radius of gyration, of cis -1,4-PB chains close to flat crystalline silica surfaces. Apart from PB, there are some simulation works concerning nanocomposites of spherical NPs, including silica, embedded in other polymer matrices.…”

Design Principles of Interfacial Dynamic Bonds in Self‐Healing Materials: What are the Parameters?

“…While the former governs the segmental dynamics and mean square displacement of polymer chains, the latter decides the strength and conformational relaxations of the polymer chains. [38][39][40][41][42][43][44][45][46][47][48][49][50][51] Such a concept is critical to optimize the healing efficiency via interdiffusion of mobile polymer chains across the cut surfaces in addition to the supramolecular networks that exchange the newly formed dangling free groups (within the fracture region), enabling reconstruction. In this article, we outline the latest developments in self-healing polymers and SH-PNCs literature and provide insights into materials design and healing mechanisms.…”

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

“…As readily seen in Figure 1 a, the surface of amorphous silica is not planar and the silanol groups orient towards the polymer film, resulting in an effective nanoroughness of the solid surface. Notice that these local regions where the surface is uneven are not distributed regularly, as is the case of the crystalline form of silica or coarse-grained models of rough surfaces [ 27 , 28 , 49 ]. Such a nanoscale roughness is also likely to be found in systems containing functionalized graphene nanofillers, such as graphene oxide [ 42 , 43 , 44 ], where the nanowrinkling of the graphene contributes significantly to the heterogeneous character of the solid filler in addition to the hydroxyl and epoxide groups attached to the surface.…”

“…Concerning the silica-filled rubber compounds, uniformly dispersed silica nanofillers in cross-linked polybutadiene matrix were simulated in atomistic detail by applying reverse mapping of the well-equilibrated coarse-grained systems [ 47 , 48 ]. Kempfer et al studied a cis -1,4-polybutadiene (PB) film confined between silica planes [ 49 ] and nanocomposites composed of the same polymer and filled with bare and grafted silica nanoparticles [ 50 ]. The authors based their model of silica on its crystalline -cristobalite form [ 49 , 50 ], resulting in a regular structure of slab and, thus, also of its boundary atoms [ 49 ].…”

“…Kempfer et al studied a cis -1,4-polybutadiene (PB) film confined between silica planes [ 49 ] and nanocomposites composed of the same polymer and filled with bare and grafted silica nanoparticles [ 50 ]. The authors based their model of silica on its crystalline -cristobalite form [ 49 , 50 ], resulting in a regular structure of slab and, thus, also of its boundary atoms [ 49 ]. When comparing the behavior of PB chains adsorbed on a highly ordered silica slab and on its annealed and less ordered version, a change in the shape as well as in the positions of the minima in the density profile was observed in the case of the annealed silica surface, pointing out a different packing of the chains near rough surface in comparison to the regular -cristobalite form.…”