Glass Transition Temperature Regulates Mechanical Performance in Nacre‐Mimetic Nanocomposites

Abstract

Nacre with its brick and mortar architecture continues to be one role model for such composites, which are tackled by several preparation routes to realize highly reinforced nanocomposites (>50 wt% of platelets), including layer-by-layer (LbL), [6] multi-layer deposition, [7] filtration, [8-11] directional freezing, [12-14] 3D printing, [15] and evaporative self-assembly. [16,17] Such methods vary in terms of time-consumption, scalability, and total amount of steps, yet still provide an efficient and controllable structure. Additionally, different reinforcements have been useful to provide a nacrelike structure, among them, clays, [11,16,18,19] graphene, [20-22] mxene, [10,23] glass, [8,9] lignocellulose, [14] and even polymer-based systems. [24,25] Furthermore, the variation of the size and aspect ratio (d/t) of the reinforcement has allowed to obtain control over the structure formation, deformation mechanisms, and mechanical properties, demonstrating the importance of a precise architecture. [17] Finally, the design of the soft-phase polymer matrix has also been an important focus of study. Traditionally, commercial hydrophilic polymers like polyvinylalcohol (PVA), polyvinylamine (PVAm) or polyethylene oxide (PEO) were used, which however presently limits the understanding as their properties are not tailor-made for understanding the overall mechanical behavior. [17,26,27] Detailed engineering of the polymer structure allowed to introduce new functionalities and dynamics within the internal structure of the nanocomposites through supramolecular bonds in dissociative networks. [21,28,29] Despite these advances, it is interesting to note that there are several fundamentally important issues that have not been addressed at all so far. To date, it is unknown how the glass transition temperature of polymers in a highly reinforced nanoclay/polymer nacre-mimetic with nanoconfined polymer layers would influence the mechanical properties. There have been attempts to discuss these properties by plasticization using swelling with water and humidity, but this also alters the nanoscale periodicities and cohesive interactions. [30,31] A detailed study of the thermo-mechanical behavior in nacremimetic nanocomposites, without the addition of swelling solvent would clearly benefit the research field and improve an understanding of how the polymer properties govern the energy dissipation in the material. Herein we systematically design a copolymer structure able to offer different thermal transitions as a function of the composition, while maintaining overall a non-ionic character to smoothly integrate into nanoclay/ polymer-based nacre-mimetics by film casting and evaporative Although research in bioinspired nanocomposites is delivering mechanically superior nanocomposite materials, there remain gaps in understanding some fundamental design principles. This article discusses how the mechanical properties of nacre-mimetic polymer/nanoclay nanocomposites with nanoconfined polymer layers are controlled by the thermo-mechanical po...

Assembling Lipoic Acid and Nanoclay into Nacre-Mimetic Nanocomposites

“…(d) Comparison of ductility of p­(LATEOA) with the reported nacre-mimetic polymer/MTM composites. Abbreviations and references: PDADMAC = poly­(diallyldimethyl­ammonium chloride), CNF = cellulose nanofiber, − CMC = sodium carboxymethyl cellulose, , PVA = poly­(vinyl alcohol), , PEO = poly­(ethylene oxide), HEC= hydroxy­ethylcellulose, ALG = alginate, PVAm = polyvinylamine, KGM = konjac glucomannan, EG/DMAm = poly­(ethylene glycol methyl ether methacrylate- co - N , N -dimethyl­acrylamide), and PDMS = polydimethyl­siloxane . (e) Origami of different shapes made by using p­(LATEOA)/MTM-70.…”

“…The hard inorganic plates contribute to stiffness and rigidness, while the soft organic layer is considered as the key to the remarkable toughness due to its lubricant-like properties. , Inspired by nature, mimicking the structure of nacre has become an attractive approach to fabricate artificial materials with high mechanical performance. − To construct the layered arrangements, the inorganic component needs to have a high aspect ratio. At the same time, hydrophilic polymers are usually introduced as the soft matrix. ,, The nature of both the inorganic (type, size, and aspect ratio) and organic composition (type, molecular weight, T g , and cross-links) significantly alters the mechanical performance of a nacre-mimetic composite. ,,− A plethora of preparation methods have been developed for nacre-like composites. Among others, a facile and green procedure has been published by Walther and co-workers, which involves evaporation-induced self-assembly of a core/shell structure formed by physical/chemical absorption of the polymer onto the inorganic component. , …”

Construction of Enhanced Photostability Anthraquinone-Type Nanovesicles Based on a Novel Two-Step Supramolecular Assembly Strategy and Their Application on Multiband Laser-Responsive Composites

“…As the doping content increases, the enhancement of the interaction between the dopant and the matrix can make loose stacking of molecular chains and destroy the crystallinity of WPU, which leads to a lower T g . 68 For the relatively high doping mass fractions, the stronger photothermal effect can more easily deform the composites. While 1,5-AQ-ODs@PS-b-PAA/WPU films cannot reach the T g under the irradiation of a 633 nm laser and 520 nm laser (Figures S14 and S16), the flower-shaped folding device has no obvious deformation (Figure S15).…”

“…41.9 °C. As the doping content increases, the enhancement of the interaction between the dopant and the matrix can make loose stacking of molecular chains and destroy the crystallinity of WPU, which leads to a lower T g . For the relatively high doping mass fractions, the stronger photothermal effect can more easily deform the composites.…”

Recyclable and Light-Adaptive Vitrimer-Based Nacre-Mimetic Nanocomposites

“…While there have been experimental developments toward nacre-mimetics with sequential layer-by-layer techniques and freeze-casting, one of the most facile, scalable and versatile techniques to realize artificial brick-and-mortar architectures is the colloidal self-assembly route using core/shell nanoplatelets that form lamellar phases upon drying. , Our previous work introduced this concept, and we investigated in detail how platelet size, glass transition temperature, and cross-linking influence the material properties. − Other groups reported on graphene-based or MXene nacre-mimetic structures following similar evaporative self-assembly. ,− We also revealed that tailored dynamics of hydrogen-bonded polymers ( i.e. , dissociative dynamic covalent bonds ) can, in fact, be used to engineer sacrificial bonds and dynamic cross-links, thereby promoting combinations of stiffness and toughness beyond what covalent (nondynamic) cross-linking could offer. − Moreover, light was proven to be a useful tool to break supramolecular bonds and weaken the mechanical properties of the nanocomposites through an induced photothermal effect. , …”