Highly Stretchable Stress-Strain Sensor from Elastomer Nanocomposites with Movable Cross-links and Ketjenblack

Light Stimuli-Responsive Degradable and Tough Polymeric Materials with Movable Cross-Links

Both strong and easily dismantlable adhesive systems are required to realize a sustainable society by recovering and reusing substrates. Introducing topological cross-links with cyclodextrins (CDs) into adhesives can improve their adhesive strength. In this study, we prepared movable cross-linked poly(ethyl acrylate) (PEA-TAcγCD) with polymerizable CDs and acid-degradable bonds (TAcγCDAAmMe) for both strong and dismantlable adhesion. The O-amidomethyl bond, which links CD to a polymerizable functional group, can be degraded by mixing Brønsted acid. By combining PEA-TAcγCD with photoacid generators, we successfully controlled the mechanical properties by cleaving the movable cross-links upon light stimulation. The degradation mechanism of TAcγCDAAmMe by photoacid generators was confirmed by mass spectrometry. In addition, the cleavage of movable cross-linking points via light stimulation was demonstrated by both the alteration of mechanical properties and chain relaxation of the system, which were evaluated by utilizing tensile tests and dynamic mechanical analysis, respectively. Therefore, the light-responsive degradable elastomer appeared applicable as an easily dismantled on-demand adhesion system. Using light stimulation, the adhesion strengths with the same or dissimilar substrates were reduced. The easy dismantling of the adhesion system by applying the acid degradability of TAcγCDAAmMe enabled excellent adhesive properties derived from the movable cross-links and easy dismantling by light stimulation. Facilitating the disassembly, collection, and reuse of resources will contribute to the realization of a sustainable society.

Stimuli-Responsive Polymer Actuator for Soft Robotics

Polymer actuators are promising, as they are widely used in various fields, such as sensors and soft robotics, for their unique properties, such as their ability to form high-quality films, sensitivity, and flexibility. In recent years, advances in structural and fabrication processes have significantly improved the reliability of polymer sensing-based actuators. Polymer actuators have attracted considerable attention for use in artificial or biohybrid systems, as they have the potential to operate under diverse conditions with high durability. This review briefly describes different types of polymer actuators and provides an understanding of their working mechanisms. It focuses on actuation modes controlled by diverse or multiple stimuli. Furthermore, it discusses the fabrication processes of polymer actuators; the fabrication process is an important consideration in the development of high-quality actuators with sensing properties for a wide range of applications in soft robotics. Additionally, the high potential of polymer actuators for use in sensing technology is examined, and the latest developments in the field of polymer actuators, such as the development of biohybrid polymers and the use of polymer actuators in 4D printing, are briefly described.

Interaction of Cyclodextrins with Amphiphilic Alternating Cooligomers Possessing the Dense Triazole Backbone

The interaction of cyclodextrins (CDs) with structure-controlled polymers is expected to provide significant insights into macromolecular recognition. However, the interaction of CDs with structure-controlled polymers has been an underexamined issue of investigation. Herein, alternating amphiphilic cooligomers (oligoCnAH, where n denotes the carbon number of alkyl groups; n = 4, 8, and 12) were synthesized by copper(I)-catalyzed azide-alkyne cycloaddition polymerization of heterodimers of 4-azido-5-hexynoic acid (AH) derivatives carrying N-alkylamide and t-butyl (tBu) ester side chains, followed by hydrolysis of the tBu ester, to study the interaction of CDs with oligoCnAH by 1H NMR, nuclear Overhauser effect spectroscopy, and pulse-field-gradient spin-echo NMR. These NMR studies indicated that αCD interacted with oligoC4AH, αCD and βCD interacted with oligoC8AH, and all CDs interacted with oligoC12AH. Based on the equilibrium models proposed, the binding constants were evaluated for the binary mixtures, which showed interaction. Comparing the interactions of the CDs/oligoC12AH binary mixtures with those of the binary mixtures of CDs and alternating copolymers of sodium maleate and dodecyl vinyl ether (polyC12M), it is concluded that oligoC12AH forms less stable micelles than does polyC12M presumably because of the lower molecular weight, the hydrophilic amide groups in the side chain, and the longer interval between neighboring C12 groups in oligoC12AH.

Simulation and experimental evaluation of laser-induced graphene on the cellulose and lignin substrates

In this article, the formation of laser-induced graphene on the two natural polymers, cellulose, and lignin, as precursors was investigated with molecular dynamics simulations and some experiments. These eco-friendly polymers provide significant industrial advantages due to their low cost, biodegradability, and recyclable aspects. It was discovered during the simulation that LIG has numerous defects and a porous structure. Carbon monoxide, H2, and water vapor are gases released by cellulose and lignin substrates. H2O and CO are released when the polymer transforms into an amorphous structure. Later on, as the amorphous structure changes into an ordered graphitic structure, H2 is released continuously. Since cellulose monomer has a higher mass proportion of oxygen (49%) than lignin monomer (29%), it emits more CO. The LIG structure contains many 5- and 7-carbon rings, which cause the structure to have bends and undulations that go out of the plane. In addition, to verify the molecular dynamics simulation results with experimental tests, we used a carbon dioxide laser to transform filter paper, as a cellulose material, and coconut shell, as a lignin material, into graphene. Surprisingly, empirical experiments confirmed the simulation results.