GIANT最新文献

In the era of smart and sustainable technology driven by naturally occurring materials, various nanocellulose-based materials play a crucial role. Shape memory behaviour and self-healing capabilities of nanocelluloses are emerging as focal points in numerous research domains. Nanocellulose and its derivatives such as cellulose nanocrystals (CNC) and cellulose nanofibers (CNF), are currently in the limelight due to their excellent shape-memory and self-healing properties, making them suitable for multifunctional devices. In this regard, CNF, as a cutting-edge material, has spurred researchers to explore its potential in developing contemporary multifunctional and personalized health devices. Therefore, a timely and comprehensive review is essential to gain deep insights into the effectiveness of shape-memory and self-healing capabilities of CNF for multifunctional devices. Herein, we first provide a brief introduction to all nanocellulose materials. This review also depicts recent advancements and breakthroughs in the large and effective synthesis of CNF-based hybrid materials. Next, focusing on their self-healing and shape-memory performance, this review sheds new light on the advanced applications of CNF materials. Finally, perspectives on the current challenges and opportunities in this field are summarized for future researchers to gain an in-depth understanding of CNF-based smart and sustainable materials.

Soft adhesive systems (SASs), which consist of a soft adhesive layer and/or soft adherends, have been extensively applied in advanced fields such as biomedicine, flexible electronics, and soft robotics. Understanding the fatigue failure of SASs is crucial for ensuring their structural safety and functional stability, as they are often subjected to fatigue loading. This paper systematically reviews the fatigue failure of SASs, aiming to provide a comprehensive understanding and contribute to the study of fatigue failure mechanisms and lifetime prediction of SASs. The review starts by introducing classical research methods for fatigue failure of adhesive systems, with a focus on total fatigue lifetime and fatigue crack growth (FCG). After summarizing the complexity of fatigue failure in SASs, it provides an overview of fatigue research for the three types of SASs: “soft interface”, “soft adherend”, and “soft-soft” adhesive systems. Then, the relations between the fatigue failure and energy dissipation of various SASs are specifically discussed noting that significant energy dissipation accompanying the cyclic deformation of SASs during fatigue loading can substantially affect the final fatigue failure of SASs. Finally, the current unresolved issues and challenges in this field are presented.

The low-temperature environment caused by solvent evaporation leads to the condensation of water vapor into water droplets that remain on the surface of the film to form breath figure patterns. The conventional approach to regulate the pore morphology in the breath figure process is to optimize the ambient temperature, humidity, and solution concentration. However, realizing a wide adjustable window of pore size and uniform distribution of the pore are still challenges. Here, inspired by the rainfall phenomenon, we proposed a simple and efficient method called the “raining boxing method” (RBM) for preparing porous films based on exogenously given water droplets as templates. The RBM broadened the adjustable window of pore size (0.6–225 µm in this work) and solved the inherent problem of radial reduction of pore size from the film center to the edge caused by the significant difference in low-temperature duration at different locations accompanying the solvent evaporation process. Furthermore, this method could realize multi-types porous films, including surface porous films, spongy porous films, and honeycomb porous films, and could be universally applied in the casting process of various polymer solutions.

The aqueous solution of regenerated silk fibroin (RSF) is considered as the raw material to produce various silk protein-based materials, including hydrogel, film, rod and fiber, etc. with significant mechanical properties. However, the aqueous solution of RSF is usually unstable within a few days or even hours in terms of its essential properties, because the conformation of the RSF chain would spontaneously transfer from random coil to β-sheet in water. In this work, we developed a way to harvest the RSF powder through an optimized spray drying method via rapid drying at a relatively low temperature. It was demonstrated that no severe degradation and conformational transition of the RSF chain occurred during powder preparation, and the RSF powder exhibited remarkable solubility in water and long stability at room temperature. Importantly, there are no obvious differences in the mechanical properties of the silk protein-based materials made from the aqueous solution from the spray-dried RSF powder (Sp-RSF) and from fresh RSF solution. Indeed, such amorphous Sp-RSF powder, in which the protein chain was dominated by random coil conformation, not only promised as the raw material for large-scale silk protein-based products in various applications but also provided the basis for fabricating bulk silk protein materials via the untraditional processing of silk fibroin, such as molding with the help of heat and moisture.

Improving the heat resistance of bio-based and biodegradable polyesters is of great significance to extend their applications. Herein, N,N’-trans-1,4-cyclohexane-bis(pyrrolidone-4-methyl carboxylate) (T-CBPMC) was prepared through efficient Michael-addition reaction between dimethyl itaconate and trans-1,4-cyclohexanediamine. The obtained T-CBPMC was copolymerized into aliphatic poly(butylene succinate) (PBS), and a series of PBSPs copolymers with T-CBPMC (BP) molar percentages between 41−80 mol % and weight average molecular weight (M_w) values ranging between 5.77*10⁴ and 6.67*10⁴ g/mol were prepared. BP units efficiently facilitated the melting temperature (203-251 °C) and isothermal-crystallization rate (t_1/2 < 20 s) of PBSPs, endowing the highest heat resistance among commercial biodegradable polyesters, which helps maintain stable in pasteurization, high-temperature disinfection, and microwave environments. Moreover, these copolymers displayed remarkable mechanical, gas barrier properties and degradability. PBSP40-PBSP60 obtained high elastic modulus (335–872 MPa) and tensile strength (24.7–31.5 MPa), and good toughness simultaneously. Multiple-ring structures and large steric hindrance of BP units resulted in superior O₂ barrier performance than that of non-degradable PET films. Importantly, the PBSP copolyesters showed obvious degradation in water environments and relatively better enzymatic degradation. It was interesting to find that even with 70 % of the BP units, the PBSP copolyesters still retained hydrolysis ability. The resulting PBSP copolyesters open the way for alternative candidates of biodegradable packaging materials with rapid crystallization, high heat-resistance and gas barrier.

Biomass conversion is pivotal in promoting sustainability and mitigating environmental pollution. In the quest to address the daunting challenge of oil spills, bioaerogels have surfaced as a beacon of hope. Their unique attributes, including remarkable porosity, lightness, and eco-compatibility, position them as ideal candidates for this purpose. Nonetheless, their application is not without challenges. Key issues such as limited capacity for oil absorption, specificity in oil-water separation, mechanical robustness, stability, and control over buoyancy are areas of active research and development. This comprehensive review delves into the current trends and advancements in augmenting the efficacy of bioaerogel composites specifically tailored for oil spill remediation. It meticulously examines a spectrum of modification strategies. Through a detailed analysis of recent research and technological breakthroughs, the review sheds light on innovative approaches and methodologies. It underscores the potential of these advancements in elevating the performance of bioaerogel composites in the realm of oil spill management. The insights gathered here are instrumental in charting the course for future research directions. They also underscore the importance of interdisciplinary collaboration in tackling environmental crises.

Polymer network is a crucial component of hydrogels, and network imperfection is a prominent feature of polymer networks, significantly influencing the performance of hydrogels. Two essential features of network imperfection are unequal chain lengths and dangling chains, both of which have a significant impact on the mechanical properties of single-network (SN) hydrogels. However, a theoretical framework considering network imperfection in SN hydrogels is still lacking. Here, we propose a theoretical model for SN hydrogels with network imperfection to study the damage behavior during deformation, in which we adopt different chain length distributions to accurately depict the real physical characteristics of the polymer network and incorporate the normalized critical chain force for a more precise measurement of network damage. To verify our theory, we discuss the effects of model parameters on the stress-stretch responses of SN hydrogels and predict the results of uniaxial loading-unloading tests of SN hydrogels, which agree well with experimentally measured stress-stretch behaviors. Finally, we implement the constitutive model into ABAQUS as a user subroutine to study the inhomogeneous deformation of hydrogels.

Plastics, accumulating globally as microplastics in living organisms, significantly contribute to environmental issues. Current materials like polylactic acid and commercial paper face limitations due to inadequate heat and water resistance, resulting in various practical inconveniences. This study reports a high-strength, water-resistant, recyclable, and naturally degradable pure cellulose food packaging material, which is crafted from bacterial cellulose (BC) and ethyl cellulose (EC) by a straightforward filtration and scratch coating process. The use of the EC ethanol solution eliminates the need for additional binders. Remarkably, the EC-BC pure cellulose material exhibits excellent mechanical properties (tensile strength of 195.3 ± 23.2 MPa), a stability in liquid environments (136.9 ± 24.2 MPa mechanical strength after 30 minutes of immersion in water), recyclability, natural degradability, cost-effectiveness, and non-toxicity. These attributes position binder-free hybrid designs, based on cellulose structures, as a promising solution to address environmental challenges arising from the extensive use of single-use plastics.

Development of H-bonding organo-catalysts with high catalytic activity and high degree of control is significantly important for the metal-free polyesters that are potentially suitable for biomedical usage. The concomitant use of base and commercially available thiourea generally suffered from prolonged reaction time and resulted in incomplete monomer conversion in some cases. Introducing one or more (thio)urea H-bonding donating arms to the parent thiourea has been proved to be an effective method for substantially increasing the activity of thiourea H-bonding donors. Consequently, we synthesized bis-thioureas derived from binaphthyl-amine bearing different substituents and investigated their catalytic performance in ROPs of lactide in this work. The density functional theory (DFT) calculations suggested that the “activated-thiourea” mode is more preferred for the bis(thiourea) containing binaphthyl-amine framework. The bis(thiourea)/base binary systems could effectively promote the LA polymerization using benzyl alcohol as initiator. The polymerization rates and the degree of control over the polymerization are highly dependent on the structures of the bis(thiourea) and base. Bis(thiourea)/1,5,7-triazabicyclo[4.4.0]dec‑5-ene pairs exhibited highest catalytic activity compared to other bis(thiourea)/base pairs, and the turnover frequency is high up to 1980 h^–1 at 75 °C. In addition, the bulky hindrance and axial chirality of the binaphthyl-amine framework could enable stereoselective ROP of rac-LA to produce isotactic-rich and crystalline PLAs at relatively low temperature (0 °C). Mechanistic studies indicated that both enantiomorphic site control (ESC) and chain end control (CEC) concurrently occurred in the rac-LA polymerization catalyzed by bis(thiourea)/base binary systems. This work will inspire future design of H-bonding donors with high catalytic performance.

To enhance the degradation rate of poly (butylene adipate-co-terephthalate) (PBAT) in the natural environment and to investigate the effect of modified monomers on the molding and structure of copolyester fibers, a series of isosorbide modified PBAT (PBIAT) tetrapolyesters were synthesized and monofilaments were prepared by solid-state drawing in this work. The experimental results revealed that the introduction of isosorbide formed a partial block structure in the molecular chain, and that a significant improvement in the properties of heat resistance and degradability of the copolyester was observed with the introduction of isosorbide. In the research of fiber forming and structure-property relationship by isosorbide, it was found that although the monofilament orientation process was affected by the V-shape structure of isosorbide, the change of the crystal structure under stress was similar to that of polybutylene terephthalate (PBT). The PBIAT monofilaments showed a decrease in the strength at break affected by the introduction of isosorbide but they still met the requirements for textile applications.