Supramolecular ionic strength-modulating microstructures and properties of nacre-like biomimetic nanocomposites containing high loading clay

Abstract

In this study, we prepare thick nacre-like polymer clay nanocomposite films by a simple solution casting method. Nanoclay sheets with soft polymer coatings are used as ideal building blocks with intrinsic hard/soft character. The water-soluble poly(vinyl alcohol) (PVA) was chosen as an organic binder to connect each smectic clay sheet in the form of a nacre-like microstructure. The polymer-clay composite is in the form of a membrane in which the clay sheets are like stacked bricks. In addition, when applying normal stress larger than the yield stress-about 40 MPa-white shear bands develop at strains larger than 10%, much like the conditions where crazing of organic PVA is suppressed by inorganic fillers of clay sheets. Their corresponding microstructure and mechanical properties are studied using wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques and a tensile testing machine and are discussed in detail.

Mechanical, Thermal, and Microstructural Analysis of Polyvinyl Alcohol/Montmorillonite Nanocomposites

“…Due to the difference in testing rates between Zhu et al [28] and this study it is difficult to make a direct comparison since the tensile data from this research shows that UTS is affected by loading rate. However, trends in increasing MMT content are visible with Zhu et al [28] showing a maximum UTS at 4 wt.% MMT. Soundararajah et al [29] also report the highest UTS around this range for the solid-state shear milled samples at 3 wt.% MMT.…”

“…Hydrogen bonds between hydroxyl groups of the PVA and the negatively charged clay surface [25] can be formed if MMT is properly dispersed in the PVA solutions. PVA/MMT nanocomposites have been synthesized by using Layer-by-Layer (LBL) assembly [16], simple vacuum filtration [26], doctor-blading [27], solution casting [28], and water-evaporation-induced assembly method [20]. The synthesized nanocomposites not only show large improvement on mechanical properties compared to pure PVA but also exhibit excellent properties in flame resistance, barrier, and optical clarity [26].…”

Chitosan nanocomposites based on distinct inorganic fillers for biomedical applications

“…Representation of the basic units (a) Si-O tetrahedron and Al-O or Al-O octahedron present on the clay minerals [43]. (b) Representation of the different structures resulted from different clay dispersion in the polymeric matrix.…”

“…These characteristics provide MMT affinity to cations, and allow exfoliation of its layers, bonded by weak electrostatic and van der Waals interactions. [43,48]…”

Bio‐inspired layer‐by‐layer assembled hybrid films for improvement of mechanical properties

“…Both inorganic platelets and organic components were found in these familiar hierarchical structures of the tough, strong, and stiff natural materials. Inspired by these natural materials, some high mechanical performance and multifunctional hybrid materials have been fabricated . Comparing with those common materials fabricated by general method, these hybrid materials show a remarkable increase in stiffness, toughness, and strength.…”