轻质可压缩壳聚糖/石墨烯复合气凝胶的制备与性能

以石墨烯气凝胶(GA)为骨架,向其浇注壳聚糖(CS)醋酸溶液制备出多重网络结构的壳聚糖/石墨烯复合气凝胶(CGA),并探究了气凝胶的微观结构与性能的关系。采用扫描电镜、红外光谱、比表面积分析、热常数分析以及压缩性能测试等方法详细表征了材料的结构和性能。研究发现,杂化气凝胶丰富发达的孔洞结构赋予了材料轻质低密度的特性;多重网络结构的构筑,使材料具有良好的回弹性;CS与GA在界面上交联,使杂化气凝胶的压缩强度由10.02 kPa提高到99.83 kPa,弹性模量由19.75 kPa增加至244.66 kPa。这种有机-无机多重网络结构的设计,提高了GA的可压缩性,解决了GA压缩易破碎的问题。

High-Performance Self-Healing Polymers

Self-healing ability is one of the most attractive features of biological tissues,as it helps living creatures to recover physiological functions and prolongs their lifespans after unexpected injuries.Inspired by this feature,self-healing artificial polymers have been developed based on extrinsic and intrinsic designs since the 1950s.In particular,the intrinsic self-healing polymers have received enormous attention since 2001 because of their unlimited self-healing times and easy preparation.Therefore,many excellent works are reported,and our understanding of the self-healing polymer goes deeper and deeper.Self-healing is the process of the rejoining of the dynamic bonds/interactions.Therefore,the healing process involves two critical factors.One is the dynamic nature of dynamic bonds/interactions.The other is the high mobility of the polymer chains.However,the dynamic bonds/interactions are vulnerable to external forces and environmental stimuli because their bond energy is lower than that of the covalent bonds,which leads to several innate drawbacks of intrinsic self-healing polymers,such as poor mechanical properties(low fracture strength,low fracture strain,low modulus,and low fracture toughness)and poor resistance against the external environment(vulnerable to acid,alkali,or moisture).Also,since high chain mobility is also a prerequisite for intrinsic self-healing,most polymers cannot be healed in the glassy state where the polymer chains are frozen.Therefore,it is challenging to develop high-performance self-healing polymers,which not only possess high mechanical strength,toughness,and stability under ambient conditions or severe environments but also manifest high self-healing efficiency in the rubbery state or even in the glassy state.Therefore,how to overcome this challenge has become a hot topic in the field of self-healing polymers.To address the above problem,many high-performance self-healing polymers with high mechanical properties,high self-healing ability,or high environmental stability are published by using different strategies.These strategies are effective at enhancing the mechanical properties or increasing its environmental stability and are worth learning about.Our group has carried out some work in this field.In this Account,we highlight our works toward fabricating high-performance self-healing polymers.We summarize the high-performance self-healing polymers from three aspects:self-healing polymers with high mechanical properties(such as high toughness,tensile strength,stretchability,and modulus),glassy polymers capable of self-healing in the glassy state,and environmentally stable self-healing polymers.In particular,strategies based on tailoring molecular-level structure,condensed structure,and filler reinforcement are discussed in detail to construct self-healing polymers with high mechanical properties.Finally,the future development of intrinsic self-healing polymers is examined from the perspective of practical application and fundamental research.

Manipulating the antioxidative capacity of melanin-like nanoparticles by involving condensation polymerization

Melanin is ubiquitous in nature and plays important roles in physiological activities especially in keeping the oxidative balance.Both natural and synthetic melanin were synthesized via the free radical polymerization of 5,6-dihydroxyindole(DHI)monomer,which may lead to the inherent compactπ-conjugation stacking microstructures and finally results in limited antioxidative capacities.To address this issue,we have strived to involve condensation polymerization during the melanin synthetic process,aiming to disrupt the compact stacking microstructures and improve the total antioxidative performance.The resulting melaninlike nanoparticles(NPs)indeed possessed less compact stackingπ-conjugation structures and decreased density,which further demonstrated enhanced antioxidative abilities compared with conventional melanin-like polymers such as poly-5,6-dihydroxyindole(Poly-DHI)and polydopamine(PDA).Their excellent free radical scavenging capability was further confirmed by the intracellular cell protection effects against reactive oxygen species(ROS)as well as in vivo therapy for acute diseases including acute kidney injury and acute liver injury.This work would promote future work toward new types of melanin-inspired nanomaterials with tunable and improved functions beyond nature.