Systematic Study of the Nanostructures of Exfoliated Polymer Nanocomposites

Abstract

High-performance bioinspired materials have shown rapid development over the last decade. Examples are brick-and-mortar hierarchical structures, which are often achieved via solvent evaporation. Although good properties are claimed, most systems are composed of stacked or intercalated platelets. Exfoliation is a crucial step to give ultimate anisotropic properties, e.g., thermal, mechanical, and barrier properties. We propose a general framework for all the various types of micro-scale structures that should be distinguished for 2D filler nanocomposites. In particular, the exfoliated state is systematically explored by the immobilization of montmorillonite platelets via (gelatin) hydrogelation. Scattering techniques were used to evaluate this strategy at the level of the particle dispersion and the regularity of spatial arrangement. The gelatin/montmorillonite exfoliated nanostructures are fully controlled by the filler volume fraction since the observed gallery d-spacings perfectly fall onto the predicted values. Surprisingly, X-ray analysis also revealed short-and quasi long-range arrangement of the montmorillonite clay at high loading.

Affine Deformation and Self-Assembly Alignment in Hydrogel Nanocomposites

“…A degree of nonaffinity is inevitably present in hydrogels and arises from a fibrous filament bending and/or micro inhomogeneities in a determined sample . A variation in gel dynamics was also observed, with the macroscopic gels formed above 11 vol % MMT seeming to consist of fragmented networks . In addition, these MMT concentrations led to gels that contracted and displayed a lower adhesion to the substrate during drying, causing lateral shrinkage (Figure S6).…”

“…In fact, the composites show a nacre-like structure in which MMT platelets are oriented perpendicular to the direction of hydrogel drying. In addition, our previous wide-angle X-ray scattering (WAXS) and focused ion beam scanning electron microscopy (FIB-SEM) analyses show that the polymer is homogeneously distributed within the lamellae, resulting in exfoliated nanostructures …”

“…For basic interpretation and data curation of the X-ray diffraction, Bruker software (DiffracSuite.EVA version 5.1, Bruker, USA) was used. From the obtained 2D-XRD results, the radial integrations and particle dispersion analysis thereof can be found at Espíndola et al (2023) …”

“…The Na-MMT thickness was 1 nm. We have indirectly measured, via FIB-SEM, the average length of 212 ± 97 nm of dispersed nanoparticles in composite cross-section . All chemicals used were of analytical grade.…”

“…One advantage of such a mechanism comes from nanoparticle immobilization with the aid of an appropriate matrix solvent, thus initially preventing loss of filler aspect ratio. This translates to nanostructures that are effectively exfoliated/intercalated and well-aligned, 39 which is crucial for final material properties, for example, gas transport and mechanical properties. Even though this mechanism serves as a separate nacre-inspired strategy, many studies have resulted in a similar composite preparation method via trial and error.…”