Molecular Dynamics Simulations of Nanocomposites Based on Poly(ε-caprolactone) Grafted on Montmorillonite Clay

Abstract

Intercalated and exfoliated models of polymer nanocomposites based on poly(epsilon-caprolactone) and functionalized montmorillonite clay are studied by means of molecular dynamics simulations. Intercalated and exfoliated models are considered for probing the structural characteristics of the corresponding nanocomposites prepared by melt intercalation and in situ polymerization, respectively. In the exfoliated system, the organization of the polymer chains onto the clay surface is examined in terms of the density profiles and the order parameter function. A layered structure can clearly be seen to form near the surface with density maxima higher than in amorphous poly(epsilon-caprolactone). This can be viewed as an increase in effective particle thickness, which can contribute to the outstanding gas barrier properties of the exfoliated nanocomposites. The comparison of the structures and energetics of the intercalated model with those of a nanocomposite model based on a nonfunctionalized clay indicates nearly similar characteristics. Nevertheless, the slight differences observed for the interfacial polymer density and clay- and surfactant-polymer binding energies can account for the differences in rheological measurements. The results also suggest that the difference in morphology obtained for the nanocomposites prepared by the two synthetic approaches can be ascribed to both a difference in interfacial polymer density and the formation of bridging polymer chain structures that hinder the exfoliation process.

Novel Cationic RAFT‐Mediated Polystyrene/Clay Nanocomposites: Synthesis, Characterization, and Thermal Stability

“…The exfoliated structure has also been obtained by many other researchers who recorded polymer growth taking place from the clay surface 26, 27, 30, 34. The exfoliated structure is mainly created by the pressure exerted on the clay sheets by the growing polymer chains within the interlayer space 63. Since TEM imaging gives a picture of only a very small portion of the sample,64 the exfoliated morphology was further confirmed by SAXS, as it allows one to look at the average morphology of the whole sample.…”

Polymer−Clay Nanocomposites: A Multiscale Molecular Modeling Approach

“…It is wellknown, both from simulation [14][15][16][43][44][45][46][47] and from experimental studies, 32,34 that the presence of layered silicates in a polymer matrix causes modifications in the chain conformation next to the particle surface. In particular, considering the density of the organic species, there seems to be a tendency of the quats and polymer chains to adopt a layered conformation.…”

Use of clay-anchored reactive modifier for the synthesis of poly (styrene-co-butyl acrylate)/clay nanocomposite via in situ AGET ATRP

“…As it is clear, incomplete exfoliation of clay layers is attributed to the competition between monomers and solvent for intercalation into the clay galleries [44] which is resulted in a reduction in the copolymer content inside the clay galleries. Therefore, copolymer chains pressure on the clay layers cannot be sufficient to delaminate the clay stacks [44,45]. In addition, partial exfoliation of clay layers in the copolymer matrix can be attributed to the weak interaction between the monomer and clay modifier, the number of attached chains, and molecular weight of copolymer chains.…”