Biobased Composites with High Lignin Content and Excellent Mechanical Properties toward the Ingenious Photoresponsive Actuator

Development of lignin-based 3D-printable light responsive shape memory materials: Design of optically controlled devices

This study employs simple approaches involving melt blending and Fused Deposition Modeling (FDM) 3D printing to fabricate a light-responsive shape memory composite. And, this composite material is used for the design of optically controlled devices that mimics the blooming of flowers in the natural environment. The composite material utilizes poly(ε-caprolactone) (PCL) and thermoplastic polyurethane (TPU) as the matrix, with lignin (L) serving as a functional filler. The analysis indicates that, due to the excellent photothermal conversion efficiency of lignin, under constant illumination the shape memory materials heat up to 50 °C within 40 s, the shape recovery rate exceeds 95.06 %. Lignin ameliorated the rheological deficiencies of TPU, with the composite material viscosity decreasing from 103 to 101 at an angular frequency of 100 rad/s, enhancing its compatibility with FDM processes. This research offers greater economic efficiency compared to conventional light-responsive materials and a simpler production method.

Synthesis of Photoresponsive Fast Self-healing Polyolefin Composites by Nickel-Catalyzed Copolymerization of Ethylene and Lignin Cluster Monomers

Polymers may suffer from sudden mechanical damages during long-term use under various harsh operating environments. Rapid and real-time self-healing will extend their service life, which is particularly attractive in the context of circular economy. In this work, a lignin cluster polymerization strategy (LCPS) was designed to prepare a series of lignin functionalized polyolefin composites with excellent mechanical properties through nickel catalyzed copolymerization of ethylene and lignin cluster monomers. These composites can achieve rapid self-healing within 30 seconds under a variety of extreme usage environments (underwater, seawater, extremely low temperatures as low as -60 °C, organic solvents, acid/alkali solvents, etc.), which is of great significance for real-time self-healing of sudden mechanical damage. More importantly, the dynamic cross-linking network within these composites enable great re-processability and amazing sealing performances.

Strong and ultrafast stimulus-healable lignin-based composite elastomers with excellent adhesion properties

With the increased environmental issues, advanced high-performance and multifunctional polymeric materials derived from biomass have tremendous attention due to the great potential to replace their traditional petroleum-based counterparts. In this work, a series of lignin graft copolymers, lignin-graft-poly(n-butyl acrylate-co-acrylic acid) (Lig-g-P(BA-co-AA)), were rationally prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. These lignin-based copolymers demonstrate good thermal stability and tunable glass transition temperature (Tg) values. The mechanical performance, including tensile strength, extensibility, Young's modulus, and toughness can be facilely adjusted by the BA/AA feed ratio and lignin content during polymerization. Owing to the extraordinary photothermal conversion ability of lignin, the Lig-B550 copolymer, containing 11.8 wt% lignin content, shows excellent stimulus-healing behavior within 1 min with a 97.1 % healing efficiency under near-infrared (NIR) laser irradiation. Moreover, the Lig-g-P(BA-co-AA) copolymers exhibit remarkable adhesion property, broadening their potential applications in the adhesive area. This grafting strategy is versatile and efficient, conferring the resultant lignin-based composite elastomers with dramatically enhanced mechanical properties and unprecedented photothermal behavior, which can inspire the further development of strong lignin-based sustainable elastomers.

4D printing light-driven actuator with lignin photothermal conversion module

Light-responsive shape memory polymers are attractive as they can be activated through remote and spatially-controlled light. In this work, 4D printing of poly(lactic acid) (PLA) composites with a near-infrared light-responsive was achieved by using the simple melt blending method and adding 3 wt% of lignin. Lignin with a conjugated structure was used as the photothermal conversion module. The composites exhibited significant photothermal effects under near-infrared (808 nm) laser irradiation, and the laser irradiation was also effective in initiating and controlling the shape memory. The structure of lignin can be improved by the action of dicumyl peroxide (DCP) to enhance the interfacial adhesion between polyamide elastomer (PAE) and polylactic acid (PLA), reduce the size of dispersed phases, and serve as an effective rheological modifier to exhibit the ideal melt viscosity required for 3D printing of composites. The good mechanical, thermal stability, and rheological properties provide assurance for the 4D printing of composites. This research provides an environmentally friendly and practical method for creating composites that have the potential to serve as ideal actuator components in a range of applications.

Design of sustainable 3D printable polylactic acid composites with high lignin content

In this study, we report the development of a sustainable polymer system with 50 wt% lignin content, suitable for additive manufacturing and high value-added utilization of lignin. The plasticized polylactic acid (PLA) was incorporated with lignin to develop the bendable and malleable green composites with excellent 3D printing adaptability. The biocomposites exhibit increases of 765.54 % and 125.27 % in both elongation and toughness, respectively. The plasticizer enhances the dispersion of lignin and the molecular mobility of the PLA chains. The good dispersion of lignin particles within the structure and the reduction of chemical cross-linking promote the local relaxation of the polymer chains. The good local relaxation of the polymer chains and the high flexibility allow to obtain a better integration between the printed layers with good printability. This research demonstrates the promising potential of this composite system for sustainable manufacturing and provides insights into novel material design for high-value applications of lignin.

Photothermal Conversion of Hydrogel-Based Biomaterial

Traditional energy from fossil fuels like petroleum and coal is limited and contributes to global environmental pollution and climate change. Developing sustainable and eco-friendly energy is crucial for addressing significant challenges such as climate change, energy dilemma and achieving the long-term development of human society. Biomass hydrogels, which are easily synthesized and modified, have diverse sources and can be designed for different applications. They are being extensively researched for their applications in artificial intelligence, flexible sensing, biomedicine, and food packaging. The article summarizes recent advances in the preparation and applications of biomass-based photothermal conversion hydrogels, discussing the light source, photothermal agents, matrix, and preparation methods in detail. It also explores the use of these hydrogels in seawater desalination, photothermal therapy, antibacterial agents, and light-activated materials, offering new ideas for developing sustainable, efficient, and advanced photothermal conversion biomass hydrogel materials. The article concludes with suggestions for future research, highlighting the challenges and prospects in this field and paving the way for developing of long-lasting, efficient energy materials.

Research Progress and Prospect of Stimuli-Responsive Lignin Functional Materials

As the world's second most abundant renewable natural phenolic polymer after cellulose, lignin is an extremely complex, amorphous, highly cross-linked class of aromatic polyphenolic macromolecules. Due to its special aromatic structure, lignin is considered to be one of the most suitable candidates to replace fossil materials, thus the research on lignin functional materials has received extensive attention. Because lignin has stimuli-sensitive groups such as phenolic hydroxyl, hydroxyl, and carboxyl, the preparation of stimuli-responsive lignin-based functional materials by combining lignin with some stimuli-responsive polymers is a current research hotspot. Therefore, this article will review the research progress of stimuli-responsive lignin-based functional materials in order to guide the subsequent work. Firstly, we elaborate the source and preparation of lignin and various types of lignin pretreatment methods. We then sort out and discuss the preparation of lignin stimulus-responsive functional materials according to different stimuli (pH, light, temperature, ions, etc.). Finally, we further envision the scope and potential value of lignin stimulus-responsive functional materials for applications in actuators, optical coding, optical switches, solar photothermal converters, tissue engineering, and biomedicine.

Lignin, the Lignification Process, and Advanced, Lignin-Based Materials

At a time when environmental considerations are increasingly pushing for the application of circular economy concepts in materials science, lignin stands out as an under-used but promising and environmentally benign building block. This review focuses (A) on understanding what we mean with lignin, i.e., where it can be found and how it is produced in plants, devoting particular attention to the identity of lignols (including ferulates that are instrumental for integrating lignin with cell wall polysaccharides) and to the details of their coupling reactions and (B) on providing an overview how lignin can actually be employed as a component of materials in healthcare and energy applications, finally paying specific attention to the use of lignin in the development of organic shape-memory materials.

3D printing with high content of lignin enabled by introducing polyurethane

The efficient utilization of lignin in 3D printing had attracted increasing attention using this abundant and eco-friendly material. However, the large-scale utilization of lignin in 3D printing remains a great challenge due to its inherent brittleness and non-thermoplasticity. In this study, thermoplastic polyurethane (TPU) was introduced to regulate the rheological properties of lignin for 3D printing. The Lignin/TPU composite of 3D printing exhibited a smooth surface, non-plastic, warm wood touch, and natural color at 50 wt% lignin loading. To further improve the mechanical properties of the composite, carbon fiber (CF) was added to the Lignin/TPU composite. The resulting CF/Lignin/TPU composites possessed 1.7 times higher tensile strength and 2.4 times higher elongation at break compared to Lignin/TPU composite. Meanwhile, the smooth surface of filament and dense interlayer bonds of printed specimens are also achieved. This work provides new insights to realize the high-value utilization of lignin and expands the practical application of lignin in 3D printing.