The development of more sustainable materials with a prolonged useful lifetime is a key requirement for a transition towards a more circular economy. However, polymer materials that are long-lasting and highly durable also tend to have a limited application potential for re-use. This is because such materials derive their durable properties from a high degree of chemical connectivity, resulting in rigid meshes or networks of polymer chains with a high intrinsic resistance to deformation. Once such polymers are fully synthesised, thermal (re)processing becomes hard (or impossible) to achieve without damaging the degree of chemical connectivity, and most recycling options quickly lead to a drop or even loss of material properties. In this context, both academic and industrial researchers have taken a keen interest in materials design that combines high degrees of chemical connectivity with an improved thermal (re)processability, mediated through a dynamic exchange reaction of covalent bonds. In particular vitrimer materials offer a promising concept because they completely maintain their degree of chemical connectivity at all times, yet can show a clear thermally driven plasticity and liquid behavior, enabled through rapid bond rearrangement reactions within the network. In the past decade, many suitable dynamic covalent chemistries were developed to create vitrimer materials, and are now applicable to a wide range of polymer matrices. The material properties of vitrimers, however, do not solely rely on the chemical structure of the polymer matrix, but also on the chemical reactivity of the dynamic bonds. Thus, chemical reactivity considerations become an integral part of material design, which has to take into account for example catalytic and cross-reactivity effects. This mini-review will aim to provide an overview of recent efforts aimed at understanding and controlling dynamic cross-linking reactions within vitrimers, and how directing this chemical reactivity can be used as a handle to steer material properties. Hence, it is shown how a focus on a fundamental chemical understanding can pave the way towards new sustainable materials and applications.

https://pubs.rsc.org/en/content/articlepdf/2020/SC/D0SC01069C

Vitrimers: directing chemical reactivity to control material properties

Recently, flexible wearable electronic devices have attracted immense interest as an alternative for conventional rigid metallic conductors in personal healthcare monitoring, human motion detection, and sensory skins, owing to their intrinsic characteristics. However, the practical applications of most wearable sensors are generally limited by their poor stretchability and sensitivity, unsatisfactory strength, lower conductivity, and single sensory function. Here a hydrogen bond cross-linked network based on carboxylic styrene butadiene rubber (XSBR) and hydrophilic sericin (SS) non-covalently modified carbon nanotubes (CNTs) is rationally designed and then fabricated into multi-functional sensors. The resultant versatile sensors are able to detect both weak and large deformations, which owns a low detection limit of 1% strain, high stretchability up to 217%, superior strength of 12.58 MPa, high sensitivity with a gauge factor up to 25.98, high conductivity of 0.071 S m-1 , and lower percolation threshold of 0.504 wt%. Moreover, the prepared sensors also possess an impressively thermal response (0.01636 °C-1 ) and realize the application in the measurement of human body temperature. The multifunctional and scalable XSBR/SSCNT sensor with the integrated tracking capabilities of real-time and in situ physiological signals, providing a promising route to develop wearable artificial intelligence in human health and sporting applications.

A High-Performance, Sensitive, Wearable Multifunctional Sensor Based on Rubber/CNT for Human Motion and Skin Temperature Detection

The evolution of self-healing polymers has resulted in a myriad of healing designs that have given way to complex systems capable of supporting multiple cycles, among other features. This progression enables us to propose the implementation of a timeline that classifies self-healing polymers in generations based on the healing mechanism, and correlated with historical development. The first generation employed the encapsulation of external healing agents; the second one, based on intrinsic mechanisms, applied reversible chemistries; and the third generation was inspired by natural examples such as plants and human skin, in which the healing agent is embedded in vascular networks. Despite great efforts and, with a few exceptions, polymers with high healing efficiency and high mechanical performance are not common. To improve this situation, a combination of different mechanisms is currently emerging, giving birth to the fourth generation of self-healing materials. This article, focused on self-healing elastomers, provides a rigorous overview of this new generation, in which the combination of covalent bonds and non-covalent interactions provides an optimal balance between mechanical performance and repairability. The implementation of this concept leads to materials with real commercial potential in functional applications, such as coatings, sensors, actuators, controlled release of drugs, seals, gaskets, hoses, and even high-performance applications such as tires and railway components.

/pdf/evolution-of-self-healing-elastomers-from-extrinsic-to-2ng2zi4az8.pdf

Evolution of self-healing elastomers, from extrinsic to combined intrinsic mechanisms: a review

A review on self-healing polymers for soft robotics

Adopting robust, stretchable, recyclable and self-healable elastomers composed of renewable resources is of great importance, but is rarely reported due to the irreversible cross-linked network. Here, we propose a simple and efficient method to prepare a robust and stretchable rubber network with recyclable and self-healable capabilities. TEMPO oxidized cellulose nanocrystals (TOCNs) with a large number of carboxyl groups were used as both the reinforcement phase and covalent cross-linkers for epoxidized natural rubber (ENR). FTIR results indicate that interfacial ester bonds were formed between carboxyl groups and epoxy groups. The covalent rubber network exhibited high tensile stress (>5 MPa) and fracture strain (>600%). Additionally, the network with exchangeable β-hydroxyl ester bonds at the rubber–TOCN interface can alter the network topology via transesterification reactions at evaluated temperatures. Therefore, the samples can achieve up to ∼85% recovery efficiency and ∼80% self-healing efficiency, exhibiting excellent reprocessing and self-healing behaviors. In addition, the samples can also be used as substrates for preparing flexible electronic devices, which exhibited excellent self-healing of electrical conductivity after damage.

A robust and stretchable cross-linked rubber network with recyclable and self-healable capabilities based on dynamic covalent bonds

Design of self-healable supramolecular hybrid network based on carboxylated styrene butadiene rubber and nano-chitosan.

The universal strategy for designing commodity rubbers to obtain high mechanical performances mainly relies on two aspects: either a developed crosslink network or an effective filler-reinforcing system. However, recycling of rubbers cannot bypass them. In this paper, strengthened and recyclable shape memory carboxylated styrene-butadiene rubber (XSBR)/carboxymethyl chitosan (CMCS) films are prepared by concentrating a mixture of XSBR latex and CMCS solution. During this process, the CMCS was regenerated due to water evaporation and synchronously entangled with XSBR chains, which constructed a mutually physical crosslink network via hydrogen bonding. With the increasing content of CMCS, regenerated CMCS changed its morphology from typical nanoparticles to nano-fibrils. When the CMCS content exceeded 10 wt%, a rigid CMCS nano-capillary network was formed in the films, constructing a special “reinforced concrete structure”. This rigid CMCS nano-capillary network significantly improves the mechanical properties of the XSBR/CMCS films. At the same time, due to the capillary network running through the whole film, the XSBR could be recycled by soaking films in water without any retained CMCS. Furthermore, our XSBR/CMCS films exhibited impressive shape memory behavior in a coincidental temperature range which is quite suitable for designing a smart medical device for the human body, e.g. a band-aid for bone fracture.

Strengthened, recyclable shape memory rubber films with a rigid filler nano-capillary network

A novel supramolecular network based on carboxylic styrene butadiene rubber (XSBR) and chitosan (CTS) is prepared through solution mixing process. XSBR molecular chains have strong interactions with extended CTS via the formation of ammonium carboxylates bridging crosslinks and hydrogen bonds, which efficiently prevent extended CTS from reagglomerating. Compared with CTS nanoparticles, unfolded CTS expose more amino and hydroxyl groups to XSBR, which results in a denser and stronger network structure. However, because of the rigidity of CTS molecule, unfolded CTS construct a rigid framing in the supramolecular network, which reduces the extensibility of the XSBR/CTS composites. Interestingly, the solution mixing retains abundant air bubbles in the XSBR/CTS solution, which turns out a porous composite.

Preparation of carboxylic styrene butadiene rubber/chitosan composites with dense supramolecular network via solution mixing process

Design of healable epoxy composite based on β-hydroxyl esters crosslinked networks by using carboxylated cellulose nanocrystals as crosslinker

Strengthened, conductivity-tunable, and low solvent-sensitive flexible conductive rubber films with a Zn2+-crosslinked one-body segregated network

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Wenchao Wu

Author Tools

Chat about Author