Programming Liquid Crystalline Elastomer Networks with Dynamic Covalent Bonds

A liquid crystalline elastomer (LCE) network consisting of dynamic covalent bonds (DCBs) is referred as a LCE vitrimer. The mesogen alignment and the network topology can be reprogrammed locally in the LCE vitrimer by activating the bond exchange reactions using an external stimulus. After removal of the external stress, a new network is formed and the reprogrammed shape can be fixed, leading to a different set of the physical properties of the LCE vitrimers. Herein, this type of emerging materials is reviewed by a brief introduction of the fundamentals of LCEs, followed by discussions of various DCBs and the design principles for LCE vitrimers. After a presentation of different strategies to improve the stability and reprogrammability of the registered mesogen alignment, approaches to prepare LCE vitrimers with complex shapes and their actuations are discussed. Potential applications such as self-healing and recycling, mechanochromic effects, and post-functionalization of nanopores are also reviewed, followed by the conclusion of the remaining challenges and opportunities.     

Dynamic bond exchangeable thermoset vitrimers in 3D-printing

Dynamic bond exchanging vitrimers have emerged recently due to their malleability, self-heal ability, recyclability, and mechanical stability. Likewise, 3D printing is consciously introduced at different platforms for ease of fabrication, high throughput, cost-effectiveness, and waste reduction. These two distinctive techniques have recently made their consensus performance, resulting from a phenomenal change in the printing field. Conventionally, thermoplastic inks have been primarily used in 3D printing, owing to their effortless processability. At the same time, thermosets were utilized for their superior mechanical strength. However, these two essential properties have been required to be presented in the printed material. In that scenario, thermoset vitrimer materials have been introduced in 3D printing, where malleability and mechanical stability have been observed in the same material. Thus, this article details the recent vitrimer material included with the different 3D printing system systems with their reported results to understand and make them widespread. Eventually, the outlook and perspectives could be helpful to understand and enhance this specific field.     

Self-Boosting Vaccination Based on Pulsatile Antigen Release from Core–Shell Microparticles (Small 18/2023)

Vaccination is among the most effective ways to prevent infectious diseases. Subunit vaccines are safe but usually require multiple booster shots, which may lead to immunity loss and economic consume. In this study, a self-boosting vaccine is developed based on the pulsatile release of antigen from the core–shell microparticle after single-injection immunization. Self-healing technology applied to form an “antigen core” can avoid organic solvents from destroying the spatial structure of the antigen. The “antigen shell” is built-up by self-assemble of the antigen with the opposite charged polypeptide. Primary immunization occurs with the self-assembled film disintegration, and the booster comes with the microparticle degradation. The changing of antigen-specific antibodies after immunization with the core–shell microparticle vaccine is consistent with that caused by the two shots of immunization. The immune effect and safety evaluation results support the translational potential of this self-boosting core–shell microparticle vaccine.     

Hydrophobized Hydrogels: Construction Strategies,Properties, and Biomedical Applications

Hydrogels, as 3D networks containing huge amount of water, display similarity to soft tissues, and thus they are of wide interest in tissue engineering. Hydrogels, due to biocompatibility and porous structure, are valuable therapeutic platforms for hydrophilic drugs. Over the last decade, there has been a strong emphasis on the development of hydrogel platforms with the ability to increase the solubility of hydrophobic drugs. However, the pronounced discrepancy between the hydrophilic character of hydrogels and the hydrophobic nature of numerous pharmacologically active compounds is problematic. In recent years, different strategies are applied using special polymer constructs or composite materials exploiting the advanced scientific knowledge in the area of polymer and lipid-based nano- and microcarriers hydrophobization of the hydrogel turns out to be not only valuable in terms of achieving the ability to dissolve poorly soluble drugs in water, but also proves to be crucial in obtaining bioadhesion in wet conditions, but also, unexpected abnormal water swelling behavior, as well as in mechanical properties such as the dissipation mechanism and self-healable hydrogel properties. This review is mainly focused on recent advances in the usage of hydrophobized hydrogels in biomedical applications.     

Electrically Functional Self-Healing Polymers: Design,Assessment, and Progress

Self-healing is a natural characteristic observed in organisms capable of repairing themselves following mechanical damage. Inspired by this attractive feature, researchers have developed self-healing polymers with various functionalities to create advanced self-healing devices that offer substantially enhanced durability and longevity. This paper provides an overview of self-healing polymers and their assessment methods, followed by the design strategy for electrically functional self-healing polymers, with a particular focus on the latest research findings. Finally, the paper discusses future prospects and challenges in this field.     

Carbon Dot-Based Hydrogels: Preparations,Properties, and Applications (Small 17/2023)

Hydrogels have extremely high moisture content, which makes it very soft and excellently biocompatible. They have become an important soft material and have a wide range of applications in various fields such as biomedicine, bionic smart material, and electrochemistry. Carbon dot (CD)-based hydrogels are based on carbon dots (CDs) and auxiliary substances, forming a gel material with comprehensive properties of individual components. CDs embedding in hydrogels could not only solve their aggregation-caused quenching (ACQ) effect, but also manipulate the properties of hydrogels and even bring some novel properties, achieving a win–win situation. In this review, the preparation methods, formation mechanism, and properties of CD-based hydrogels, and their applications in biomedicine, sensing, adsorption, energy storage, and catalysis -are summarized. Finally, a brief discussion on future research directions of CD-based hydrogels will be given.     

Mussel-Inspired,Underwater Self-Healing Ionoelastomers Based on α-Lipoic Acid for Iontronics

Weak adhesion and lack of underwater self-healability hinder advancing soft iontronics particularly in wet environments like sweaty skin and biological fluids. Mussel-inspired, liquid-free ionoelastomers are reported based on seminal thermal ring-opening polymerization of a biomass molecule of α-lipoic acid (LA), followed by sequentially incorporating dopamine methacrylamide as a chain extender, N,N′-bis(acryloyl) cystamine, and lithium bis(trifluoromethanesulphonyl) imide (LiTFSI). The ionoelastomers exhibit universal adhesion to 12 substrates in both dry and wet states, superfast self-healing underwater, sensing capability for monitoring human motion, and flame retardancy. The underwater self-repairabilitiy prolongs over three months without deterioration, and sustains even when mechanical properties greatly increase. The unprecedented underwater self-mendability benefits synergistically from the maximized availability of dynamic disulfide bonds and diverse reversible noncovalent interactions endowed by carboxylic groups, catechols, and LiTFSI, along with the prevented depolymerization by LiTFSI and tunability in mechanical strength. The ionic conductivity reaches 1.4 × 10⁻⁶–2.7 × 10⁻⁵ S m⁻¹ because of partial dissociation of LiTFSI. The design rationale offers a new route for creating a wide range of LA- and sulfur-derived supramolecular (bio)polymers with superior adhesion, healability, and other functionalities, and thus has technological implications for coatings, adhesives, binders and sealants, biomedical engineering and drug delivery, wearable and flexible electronics, and human–machine interfaces.     

羟丙基壳聚糖/氧化甲基纤维素自愈合水凝胶的制备及其载药性能

采用高碘酸钠对甲基纤维素（MC）进行氧化制备了氧化甲基纤维素（DAMC），通过羟丙基壳聚糖（HPC）的氨基与DAMC的醛基发生希夫碱反应制备了HPC/DAMC自愈合水凝胶。通过调节HPC和DAMC含量探究水凝胶的微观形态、溶胀性能、力学性能、自愈合性能、体外降解以及药物缓释性能。结果表明，HPC/DAMC自愈合水凝胶具有相互连通的孔隙，且孔径处于80～375μm范围内，在室温无刺激条件下能够在20 min内实现自愈合且具有良好的拉伸性能。此外，HPC/DAMC自愈合水凝胶具有良好的保水性，其溶胀比为14.0～17.4。在溶菌酶的作用下，HPC/DAMC自愈合水凝胶在60 h时质量损失率可达84.2%～99.6%。HPC/DAMC自愈合水凝胶对抗肿瘤药物吉西他滨具有缓释效果，缓释作用长达96 h，药物累积释放率达到83.2%～92.7%。     

功能型环氧树脂基防腐涂层的研究进展

环氧树脂涂层因其优异的耐蚀性能、对金属表面良好的附着力而在金属防腐领域得到广泛应用。但涂层固化过程中会形成缺陷和孔洞，腐蚀介质可以直接接触到金属表面。为了开发出具有优良耐久性的防腐涂层，研究人员使用不同的方法和材料制备了多种环氧树脂防腐涂层。该文综述了纳米粒子改性环氧防腐涂层、超疏水型环氧防腐涂层、自修复型环氧防腐涂层、导电聚合物改性环氧防腐涂层及生物基材料改性环氧防腐涂层的制备及性能。但这5种防腐涂层各有局限性，未来应该探究出新的环氧防腐涂层，在提升涂层防腐性能的同时，兼顾其他性能，使环氧树脂基防腐涂层朝着功能化、智能化的方向发展。