Synergistic Effect of Small Molecules on Large-Scale Structure of Simplified Industrial Nanocomposites

Abstract

The microstructure of polymer nanocomposites made with disordered silica filler (Zeosil(R) 1165MP) of industrial relevance and various coating agents is quantitatively analyzed using a combination of SAXS, TEM, and a recently developed structural model. The polymer matrix is formed by an endfunctionalized styrene-butadiene statistical copolymer capable of covalent grafting on the silica nanoparticles. The effect of the coating agents with different alkyl chain length (C 8 , C 12 , and C 18 ) on filler structure quantified in terms of aggregate formation, for different concentrations (up to 8%wt with respect to silica), and the effect of a commonly added catalyzer, DPG, are studied using the structural model. As a result we show that a strongly synergetic effect of both DPG and coating agent exist. Our findings open the road to a fundamental understanding and rational design of model and industrial nanocomposite formulation with optimized coating agents.

Aggregate Formation of Surface-Modified Nanoparticles in Solvents and Polymer Nanocomposites

“…Interactions between NPs and thus their aggregation can be controlled via NP surface modification. 57,58 Bare oxide NPs are covered with -OH groups and usually carry electrostatic charges in water, contributing to their electrostatic stabilization in this solvent, as opposed to attractive short-ranged Van der Waals forces. 59 Modifications of the interface by adsorption or chemical grafting may change the number of charges, 60 or the hydrophilic/hydrophobic character of the surface, e.g., with amphiphilic molecules [61][62][63][64] .…”

Structural identification of percolation of nanoparticles

“…49,50 We have shown recently that the structure of simplified industrial polymer nanocomposites produced by solid-phase mixing of styrene-butadiene (SB) and silica can be tuned by means of a synergetic effect of two "small" molecules, diphenyl guanidine and triethoxy octylsilane, which are commonly used in car tires. 51 Here, "simplified" refers to a limited number of ingredients with a styrenebutadiene (SB) polymer of well-defined mass generating clear rheological features, while "industrial" characterizes the disordered silica filler of industrial origin. In PNCs made by solvent casting using well-defined colloidal silica grafted with silane-molecules, the dispersion in a SB matrix was recently studied at low concentration using a combination of small-angle X-ray scattering (SAXS) and reverse Monte Carlo (RMC).…”

Determination of the local density of polydisperse nanoparticle assemblies

“…We have recently recognized the depth of the correlation hole as an experimental observable to follow the structure of filler aggregates in industrial 17,22,47 and model nanocomposites 23,48 . In the present article, we have chosen a simulation approach to provide a universal tool for a large range of experiments: first, (log-normal) polydisperse hard sphere particles are created, and both "infinite" and finite NP assemblies representing aggregates of known particle density generated.…”