Effect of montmorillonite on the rheological properties of dually crosslinked guar gum‐based hydrogels

Abstract

One strategy to create chemical and physical cross‐links simultaneously is to introduce into the chemical network hydrogen bonding with clay nanofillers. Understanding the relaxation mechanisms of these systems is crucially important and has drawn the extensive interest of many scientists. In this work, the influence of different amounts of montmorillonite on the structural and rheological properties of guar gum hydrogels was investigated. Depending on the clay content, different nanostructures were identified by X‐ray diffraction (XRD) and their effect on the rheological properties of the dual hydrogels was studied. From stress and frequency sweep tests it emerged that all the samples exhibit a weak gel behavior and showed a maximum for G″ that can be ascribed to the breaking and reforming of transient physical crosslinks. This relaxation mode is more pronounced for the hydrogel for which a minimum in the swelling degree was observed. On the basis of these results, a model structure was proposed according to which the clay sheets act as effective multifunctional cross‐linkers. The more homogeneously dispersed are the clay platelets, the higher is the density of physical crosslinks. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41373.

Effects of clay concentration on the morphology and rheological properties of xanthan gum‐based hydrogels reinforced with montmorillonite particles

“…Aggregates of MTT particles are observed for higher concentrations, as shown by Figures (c,d) for H 2 and H 4 , respectively. Following the arguments of Branca et al . and the results in Figures and , it can be suggested that at lower concentrations (up to 1.0%) the MTT layers are fully and uniformly dispersed and exfoliated within the XG biopolymer matrix, whereas at higher concentrations MTT is present as composite‐tactoids.…”

“…The WAXD pattern for H 2 and H 4 exhibited a diffraction peak at the same 2θ value. Branca et al . studied guar gum‐MT hydrogels, obtaining similar WAXD patterns, where no intercalation occurred between the biopolymer chains and the clay particles.…”

“…In contrast, active fillers interact with the hydrogel components via the formation of hydrogen bonds, leading to a further consolidation of the tridimensional network . Agarose–cellulose nanowhiskers, guar gum–clay, gelatine–cellulose nanocrystals are examples of composites made of biopolymers and reinforcing particles. In particular, biopolymer–clay composites have attracted research interest because of their biocompatibility, biodegradability, and bioaccessibility properties …”

Bionanocomposites based on polysaccharides and fibrous clays for packaging applications

“…In fact, the contact of non‐modified polysaccharides with water provokes a fast swelling of the film and leads to their disintegration, making it impossible to determine their water uptake capacity [Figure (a‐)]. In contrast, the assembly of SEP and PALY to these polysaccharides significantly improves their water resistance due to their effect as physical crosslinking agents, analogously to that reported for montmorillonite sheets in a guar gum matrix, and the resulting films can maintain their integrity during and after the assay [Figure (a‐) and (a‐)]. Water absorption (pH 5.5) of the bionanocomposites as a function of the clay content is displayed in Figure (b,c).…”

Strengthening mechanism of poly(acrylamide)/graphene oxide/laponite dual nanocomposite hydrogels

“…However, due to great demands for tough hydrogels in various applications, improving the mechanical strengths of hydrogels has been an important topic over the last few decades. Nanocomposite hydrogels are identified to be a simple way of enhancing the mechanical properties of hydrogels through the addition of reinforcing organic/inorganic fillers such as Laponite, montmorillonite, and carbon nanotubes . So high tensile strength (up to 1.1 MPa) with high elongation (up to 800%) in Laponite‐based nanocomposite hydrogels is achieved .…”