A high stiffness and self-healable polyurethane based on disulfide bonds and hydrogen bonding

Dynamic chemistry based self-healing of asphalt modified by diselenide-crosslinked polyurethane elastomer

Study on waterborne self-healing polyurethane with dual dynamic units of quadruple hydrogen bonding and disulfide bonds

Synthetic materials used in a wide range of applications are prone to damage in the form of cracking/microcracking Catastrophic failure of the materials may occur due to the growth and merging of the microcracks, which results in the reduction of the service life of the materials To avoid these problems and increase the service life, early detection and mending of the microcracks are extremely important Self-healing materials can be utilized in these cases, which have the capability not only to detect cracks early but also to repair cracks automatically These materials will also have the potential to improve material reliability, extend the service life, reduce replacement costs, and improve product safety Due to these attractive features, numerous research studies are conducted every year on the development of self-healing systems This paper summarizes the latest progress in the design and fabrication techniques of self-healing materials through a wide range of materials, including metals, ceramics, concrete, and polymer composites Based on recent research, this article provides an overview of different chemistries and approaches involved in preparing self-healing composites Comparative healing efficiency and related fabrication methods are tabulated Finally, existing problems, gaps, and challenges, and future research directions and opportunities for commercial applications are highlighted

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Progress and challenges in self-healing composite materials

Shape memory polymers (SMPs) have received immense attention from materials research community thanks to their unrivaled properties such as high recoverable strains (up to 400%), low weight, tailorable properties, easy processing, and multiple activation methods. Researchers in both academia and industry have been proposing, experimenting, analyzing, and reporting on various aspects of these materials from synthesis to their applications. Such efforts have led to skyrocketing research output in terms of published papers, especially in the last half a decade. Despite the flourishing research, numerous challenges that hinder advanced applications still exist with the predominant one being the low mechanical properties. To circumvent these challenges, various types of reinforcements have been utilized, leading to significant enhancements and widened potential applications. This work presents an overview of the present research on active composites. Areas covered include the background of SMPs, reinforcements, fabrication techniques, stimulus methods, and applications. Our review is particularly unique in that we included discussions on the various fabrication techniques for SMP composites including their merits and demerits which, to the best of our knowledge, is the first review to include such discussion, thus making it a complete reference material.

Active composites based on shape memory polymers: overview, fabrication methods, applications, and future prospects

Self-healing mechanism of microcracks on waterborne polyurethane (WPU) with varied disulfide bond contents was investigated thoroughly in this paper. The self-healing process could be observed by an optical microscope, which was divided into two steps. The first step was the cohesive healing movement, closely related with microphase separations and further characterized by the Fourier transform infrared peak fitting, differential scanning calorimetry, and dynamic mechanical thermal analysis. The second step of the exchange reactions of disulfide bonds could be confirmed by the in situ Raman and tensile mechanics. In addition, the cohesive healing behavior was quantitatively described by the kinetic method, and the exchange reaction active energies of disulfide bonds were also calculated to be 20.42 kJ/mol by gel permeation chromatography tests. The best self-healing performance of SHWPUs was WPU-8, and it could be healed at 75 °C in 15 min with 100% self-healing efficiency. Combining the self-healing process observation with the kinetic analysis can provide deep insights into the self-healing mechanism of microcracks.

Self-Healing Mechanism of Microcracks on Waterborne Polyurethane with Tunable Disulfide Bond Contents.

Room‐Temperature Self‐Healing and Reprocessable Waterborne Polyurethane with Dynamically Exchangeable Disulfide Bonds

Lithium (Li) deposition behavior plays an important role in dendrite formation and the subsequent performance of lithium metal batteries. This work reveals the impact of the lithiophilic sites of lithium-alloy on the Li plating process via the first-principles calculations. We find that the Li deposition mechanisms on the Li metal and Li22Sn5 surface are different due to the lithiophilic sites. We first propose that Li plating on the Li metal surface goes through the "adsorption-reduction-desorption-heterogeneous nucleation-cluster drop" process, while it undergoes the "adsorption-reduction-growth" process on the Li22Sn5 surface. The lower adsorption energy contributes to the easy adsorption of Li on the lithiophilic sites of the Li22Sn5 surface. The lower Li reduction energy on the Li metal surface indicates that it is easy for Li to be reduced on the Li metal surface, attributed to its higher Fermi energy level. Furthermore, the faster Li diffusion on the Li22Sn5 surface results in smooth Li deposition, which is based on a "two-Li synergy diffusion" mechanism. However, Li diffuses more slowly on the Li metal surface than on the Li22Sn5 surface due to the "single Li diffusion" mechanism. This work provides a fundamental understanding on the impact of lithiophilic sites of Li alloy on the Li plating process and points out that the future design of 3D Li-alloy substrates decorated with multilithiophilic sites can prevent dendrite formation on the lithium-alloy substrate by guiding uniform Li deposition.

Regulation of Dendrite-Free Li Plating via Lithiophilic Sites on Lithium-Alloy Surface.

Rheological behaviors of asphalt binders reinforced by various fibers

Caries is the most common chronic infectious disease in the human oral cavity and the existing anti-caries agents may lead to drug resistance and microecological imbalance. A novel urea derivative, 1,3-bis[3,5-bis(trifluoromethyl)phenyl]urea, has a potentially prominent antibacterial effect on cariogenic bacterial strain Streptococcus mutans UA159. In this study, we encapsulated the water-insoluble urea derivative in poly(lactic-co-glycolic acid) (PLGA) nanoparticles, performed physicochemical characterizations and explored its potential as a caries-preventive agent. The results showed that the drug-loaded PLGA nanoparticles exhibited satisfying surface morphology, particle size, size distribution and stability. With an optimized theoretical drug loading (10%), the drug-loaded PLGA nanoparticles exhibited negligible cytotoxicity against human oral squamous cell carcinoma cells. We noticed a biphasic drug release in vitro and the rate and cumulative release was higher in an acidic environment (pH 4.5) compared to a neutral environment (pH 7.4). The drug-loaded PLGA nanoparticles significantly inhibited the growth and lactic acid production of planktonic S. mutans as well as S. mutans biofilms. Our results indicate that the novel urea derivative-loaded PLGA nanoparticles serve as a promising anti-caries agent with remarkable pharmaceutical characteristics, low cytotoxicity, and satisfying antimicrobial effect.

https://pubs.rsc.org/en/content/articlepdf/2022/ra/d1ra09314b

Mengyun Zhang

Papers

Self-Healing Mechanism of Microcracks on Waterborne Polyurethane with Tunable Disulfide Bond Contents.

Room‐Temperature Self‐Healing and Reprocessable Waterborne Polyurethane with Dynamically Exchangeable Disulfide Bonds

Regulation of Dendrite-Free Li Plating via Lithiophilic Sites on Lithium-Alloy Surface.

Rheological behaviors of asphalt binders reinforced by various fibers

Novel urea derivative-loaded PLGA nanoparticles to inhibit caries-associated Streptococcus mutans