Recent Advances in Flexible CNC-Based Chiral Nematic Film Materials

General Chiral Catalysis: A Cinchona Thiourea-Pyridoxazoline Scaffold as Both Organocatalyst and Chiral Ligand for an Enantioselective Mannich Reaction between α-Aminomaleimides and Benzothiazolimines

For proof of a new concept of general chiral catalysis, a series of new bifunctional chiral catalysts integrated with both cinchona alkaloid thiourea and pyridine-oxazoline scaffolds were devised and prepared. Using as independent organocatalysts, a new Mannich reaction between α-aminomaleimides and benzothiazolimines with acceptable enantioselectivities (up to 75% ee) has been disclosed. Served as a chiral ligand, the new organocatalyst synergically works with Cu(OTf)2 to catalyze the reaction in excellent enantioselectivities (up to 96% ee) with good yields under mild conditions even in a scale-up preparation. Both the substrates and the final multifunctional chiral adducts may provide a possibility for the development of new pharmaceutical entities and chiral ligands.

Stretchable Laminates with Tunable Structural Colors from Layered Stacks of Elastomeric, Ionic, and Natural Polymers

Natural polymers such as plant-derived cellulose nanocrystals (CNCs) are renowned for color iridescence due to their internal helical organization, but they show modest stretchability and bending abilities, because of the brittle nature of highly crystalline needlelike nanocrystals. Herein, we report the highly stretchable composite materials built from these nanocrystals and branched ionic polymers (bIPs) with terminal amine-terminated poly(N-isopropylacrylamide) (PNIPAM) stacked between elastomeric layers. These layered elastomeric composites preserve the high mechanical stretchability of polyurethane outer layers up to 150%. Furthermore, the toughness increased manyfold, due to the sequential initiation and arresting of concurrent transversal cracks within the reinforcing central nanocomposite layer. Moreover, vivid structural colors of CNC helical organization preserved within these laminated composites show the ability to respond to humidity and temperature. We suggest that these elastomeric composite laminates with preserved structural colors of helical nanocellulose organization can be considered to be promising candidates for demanding applications such as robust wearable sensors, flexible optical labels, and photonic devices.

Controlling the optical properties of chiral nematic mesoporous organosilica films with bioadditives

Chiral nematic mesoporous organosilica (CNMO) films have unique iridescent properties that make them attractive candidates for decorations, sensing and photonics. However, it has proven difficult to control the colour and porosity of CNMO films. Here, we have explored the addition of a range of biodegradable and eco-friendly additives to tune the helical pitch and, hence, the colour of the CNMO materials. It was found that the controlled integration of additives allows for the colour of the materials to be tuned across the visible spectrum, but cannot be used to tune the porosity of the films. This work opens up new prospects for preparation of CNMO materials with adjustable optical properties.

Polymerization strategy for cellulose nanocrystals-based photonic crystal films with water resisting property

Cellulose nanocrystals (CNCs) can form a liquid crystal film with a chiral nematic structure by evaporative-induced self-assembly (EISA). It has attracted much attention as a new class of photonic liquid crystal material because of its intrinsic, unique structural characteristics, and excellent optical properties. However, the CNCs-based photonic crystal films are generally prepared via the physical crosslinking strategy, which present water sensitivity. Here, we developed CNCs-g-PAM photonic crystal film by combining free radical polymerization and EISA. FT-IR, SEM, POM, XRD, TG-DTG, and UV-Vis techniques were employed to characterize the physicochemical properties and microstructure of the as-prepared films. The CNCs-g-PAM films showed a better thermo-stability than CNCs-based film. Also, the mechanical properties were significantly improved, viz., the elongation at break was 9.4 %, and tensile strength reached 18.5 Mpa, which was a much better enhancement than CNCs-based film. More importantly, the CNCs-g-PAM films can resist water dissolution for more than 24 h, which was impossible for the CNCs-based film. The present study provided a promising strategy to prepare CNCs-based photonic crystal film with high flexibility, water resistance, and optical properties for applications such as decoration, light management, and anti-counterfeiting.

Rigidity with Flexibility: Porous Triptycene Networks for Enhancing Methane Storage

In the pursuit of advancing materials for methane storage, a critical consideration arises given the prominence of natural gas (NG) as a clean transportation fuel, which holds substantial potential for alleviating the strain on both energy resources and the environment in the forthcoming decade. In this context, a novel approach is undertaken, employing the rigid triptycene as a foundational building block. This strategy is coupled with the incorporation of dichloromethane and 1,3-dichloropropane, serving as rigid and flexible linkers, respectively. This combination not only enables cost-effective fabrication but also expedites the creation of two distinct triptycene-based hypercrosslinked polymers (HCPs), identified as PTN-70 and PTN-71. Surprisingly, despite PTN-71 manifesting an inferior Brunauer-Emmett-Teller (BET) surface area when compared to the rigidly linked PTN-70, it showcases remarkably enhanced methane adsorption capabilities, particularly under high-pressure conditions. At a temperature of 275 K and a pressure of 95 bars, PTN-71 demonstrates an impressive methane adsorption capacity of 329 cm3 g-1. This exceptional performance is attributed to the unique flexible network structure of PTN-71, which exhibits a pronounced swelling response when subjected to elevated pressure conditions, thus elucidating its superior methane adsorption characteristics. The development of these advanced materials not only signifies a significant stride in the realm of methane storage but also underscores the importance of tailoring the structural attributes of hypercrosslinked polymers for optimized gas adsorption performance.