Recyclable, self-healable and reshape vitrified poly-dimethylsiloxane composite filled with renewable cellulose nanocrystal

Dynamic Covalent Chemistry of Enamine-Ones: Exploring Tunable Reactivity in Vitrimeric Polymers and Covalent Organic Frameworks

Dynamic covalent chemistry (DCC) has revolutionized the field of polymer science by offering new opportunities for the synthesis, processability, and recyclability of polymers as well as in the development of new materials with interesting properties such as vitrimers and covalent organic frameworks (COFs). Many DCC linkages have been explored for this purpose, but recently, enamine-ones have proven to be promising dynamic linkages because of their facile reversible transamination reactions under thermodynamic control. Their high stability, stimuli-responsive properties, and tunable kinetics make them promising dynamic cross-linkers in network polymers. Given the rapid developments in the field in recent years, this review provides a critical and up-to-date overview of recent developments in enamine-one chemistry, including factors that control their dynamics. The focus of the review will be on the utility of enamine-ones in designing a variety of processable and self-healable polymers with important applications in vitrimers and recyclable closed-loop polymers. The use of enamine-one linkages in crystalline polymers, known as COFs and their applications are also summarized. Finally, we provide an outlook for future developments in this field.

Catalyst-free readily dual-recyclable acetal-based covalent adaptable cellulose networks

Despite covalent adaptable networks (CANs) imparting the favorable features of crosslinked polymers, as well as the functionality of reprocessing, reshaping and welding, due to exchange reaction enabled topology changes; it is still a huge challenge to design catalyst-free, fast reprocessing, controlled degradation and polymer recyclable biomass base CANs. Herein, for the first time, acetal-based covalent adaptable cellulose networks (ACCs) were utilized to synthesize readily reconstructable cellulose-based thermosets with mechanical tunability. ACCs were synthesized via catalyst-free "click" addition of cellulose and divinyl ether without releasing small molecule byproducts. Different crosslinking densities and crosslinkers were used to explore the structure-property relationship, the mechanical and thermal properties of the ACCs were strongly influenced by these factors. ACCs can obtain enhanced tensile strength or elongation at break by changing the structure of the crosslinker. Furthermore, the reworking, welding and shape memory properties of these ACCs, based on the dynamic exchange reaction of acetal bonds, were investigated. In addition, these ACCs can be degraded under acidic conditions, and closed-loop utilization of polymer was possible. Thus, ACCs can be mechanically and chemically double-cycled, which will contribute to solving the white pollution problem and resource waste as a new class of sustainable plastics.

Self-Healing Silicone Materials: Looking Back and Moving Forward

This review is dedicated to self-healing silicone materials, which can partially or entirely restore their original characteristics after mechanical or electrical damage is caused to them, such as formed (micro)cracks, scratches, and cuts. The concept of self-healing materials originated from biomaterials (living tissues) capable of self-healing and regeneration of their functions (plants, human skin and bones, etc.). Silicones are ones of the most promising polymer matrixes to create self-healing materials. Self-healing silicones allow an increase of the service life and durability of materials and devices based on them. In this review, we provide a critical analysis of the current existing types of self-healing silicone materials and their functional properties, which can be used in biomedicine, optoelectronics, nanotechnology, additive manufacturing, soft robotics, skin-inspired electronics, protection of surfaces, etc.