Water-Involved Carbon-Nitrogen Triple-Bond Monomer Based Polymerization toward Processable Functional Polyamides under Ambient Conditions.

Polyamide plays a pivotal role in engineering thermoplastics. Constrained by the harsh conditions and arduous procedures for its industrial synthesis, developing facile synthesis of polyamides is still challengeable and holds profound significance. Herein, we successfully utilized water as one of the monomers to synthesize functional polyamides under ambient conditions. A powerful multicomponent polymerization of water, isocyanides, and chlorooximes was established in phosphate-buffered saline. Soluble and thermally stable polyamides with high weight-average molecular weights (up to 53 900) were obtained in excellent yields (up to 95 %). The polymerization exhibits unique polymerization-induced emission characteristics, successfully converting non-emissive monomers into unconventional emissive polymers. Notably, the resultant polyamides could undergo effective post-modification via the hydroxyl-yne click reaction. By incorporating various functional groups into the polyamide, its emission color could be fine-tuned from blue to green and to red. Remarkably, the refractive index (n) of the polyamide at 589 nm could be increased from 1.6173 to 1.7227 and the Δn could be unprecedentedly as high as 0.1054 for non-heavy atom-containing polymers after post-modification, and its micron-thick films exhibited excellent transparency in the visible region. Thus, this work not only establishes a powerful polymerization toward novel polyamides but also opens up an avenue for their versatile functionalization.

Preparation of strong, UV-blocking and sustainable glucose-cross-linked cellulose plastics via hydroxyl-yne click reaction.

The construction of functional cellulose plastics possessing strong UV-blocking, hydrophilicity, and biodegradability is challenging. Therefore, we provide a novel strategy to successfully prepare sustainable and hydrophilic glucose-cross-linked cellulose (GC) plastics showing effective UV-blocking and excellent mechanical properties via hydroxyl-yne click reaction at room temperature. The results demonstrated that hydroxyl-yne click chemistry enabled efficient crosslinking of cellulose with glucose using 4-dimethylamino pyridine (DMAP) as a catalyst. Moreover, the DMAP residue imparted good UV-shielding properties to GC films exhibiting nearly 100 % UVC (200-275 nm) and 100 % UVB (320-275 nm) shielding ratios. The introduction of glucose imparted superior hydrophilicity (water contact angle of 40.3-43.2°) and improved water adsorption. Additionally, the mechanical properties of the GC films increased with the increasing crosslinking density, and the highest tensile stress was 94 MPa. The water-induced breaking and hydrogen bond reforming strategy led to a stress of 127 MPa and a strain of 25.6 % for the final GC2 film, which were excellent compared to those of the most reported cellulose films. Additionally, GC films were biosafe, exhibited improved oxygen barrier, and good biodegradability. Hence, this study provides a promising and efficient approach for preparing high-performance cellulose plastics.

A tough, reversible and highly sensitive humidity actuator based on cellulose nanofiber films by intercalation modulated plasticization.

Cellulose nanofiber was an ideal candidate for humidity actuators based on its wide availability, biocompatibility and excellent hydrophilicity. However, conventional cellulose nanofiber-based actuators faced challenges like poor water resistance, flexibility, and sensitivity. Herein, water-resistant, flexible, and highly sensitive cross-linked cellulose nanofibers (CCNF) single-layer humidity actuators with remarkable reversible humidity responsiveness were prepared by combining the green click chemistry modification and intercalation modulated plasticization (IMP). The incorporation of phenyl ring and the crosslinked network structure in CCNF films contributed to its improved water resistance and mechanical properties (with a stress increased from 85.9 ± 3.1 MPa to 141.2 ± 21.5 MPa). SEM analysis confirmed enhanced interlaminar sliding properties facilitated by IMP. This resulted in increased flexibility and toughness of CCNF films, with a strain of 11.5 % and toughness of 9.9 MJ/m3. These improvements efficiently enhanced humidity sensitivity for cellulose nanofiber, with a 4.8-fold increase in bending curvature and a response time of only 3.4 ± 0.1 s. Finally, the good humidity sensitivity of modified CNF can be easily imparted to carbon nanotubes (CNTs) via simple self-assembly method, thus leading to a high-performance humidity-responsive actuator. The click chemistry modification and IMP offer a new avenue to fabricate tough, reversible and highly sensitive humidity actuator based on cellulose nanofiber.

Photocrosslinkable and hydroplasicable UV-shielding nanocellulose films facilitated by hydroxyl-yne click reaction.

Sustainably-sourced functional nanocellulose materials are vitally important for the green and sustainable development. Herein, we reported photocrosslinkable and hydroplasticable TEMPO-oxidized cellulose nanofiber phenyl propylene ketone ethers (TOCNPPK) films with excellent ultraviolet (UV) shielding, highly reversible processability, and extended mechanical properties, which were facilitated by green hydroxyl-yne click reaction. The introduction of conjugated aromatic ring and vinyl bonds (-C=C-) had been demonstrated the key for the improved overall performance of resultant TOCNPPK, which not only endowed the TOCNPPK with nearly 100 % UV shielding, but also enabled it to be formed into diverse 3D shapes (helix, ring and letters "N, F, U") via the facile hydrosetting method. The photocrosslinkable-enhanced mechanical performance of TOCNPPK films was also attributed to -C=C- which could crosslink via [2π + 2π] cycloaddition reactions under UV-irradiation. The ultimate stress of TOCNPPK films was as high as 210.0 ± 22.8 MPa and the Young's modulus was 11.5 ± 0.7 GPa, much superior to those of 128.6 ± 8.5 MPa and 9.2 ± 0.6 GPa for pristine TOCN films. Furthermore, the TOCNPPK had been demonstrated as efficient nanofillers for both hydrophilic polyvinyl alcohol and lipophilic polycaprolactone to develop advanced biodegradable composite films with the integration of good water-wetting resistance, excellent UV blocking, and photo-enhanced mechanical performance.

Facile Graphene Oxide Modification Method via Hydroxyl-yne Click Reaction for Ultrasensitive and Ultrawide Monitoring Pressure Sensors.

Enhancing the durability and functionality of existing materials through sustainable pathways and appropriate structural design represents a time- and cost-effective strategy for the development of advanced wearable devices. Herein, a facile graphene oxide (GO) modification method via the hydroxyl-yne click reaction is present for the first time. By the click coupling between propiolate esters and hydroxyl groups on GO under mild conditions, various functional molecules are successfully grafted onto the GO. The modified GO is characterized by FTIR, XRD, TGA, XPS, and contact angle, proving significantly improved dispersibility in various solvents. Besides the high efficiency, high selectivity, and mild reaction conditions, this method is highly practical and accessible, avoiding the need for prefunctionalizations, metals, or toxic reagents. Subsequently, a rGO-PDMS sponge-based piezoresistive sensor developed by modified GO-P2 as the sensitive material exhibits impressive performance: high sensitivity (335 kPa-1, 0.8-150 kPa), wide linear range (>500 kPa), low detection limit (0.8 kPa), and long-lasting durability (>5000 cycles). Various practical applications have been demonstrated, including body joint movement recognition and real-time monitoring of subtle movements. These results prove the practicality of the methodology and make the rGO-PDMS sponge-based pressure sensor a real candidate for a wide array of wearable applications.