Self-healing polymeric gel via RAFT polymerization and Diels–Alder click chemistry

Bio-Vitrimers for Sustainable Circular Bio-Economy

The aim to achieve sustainable development goals (SDG) and cut CO₂-emission is forcing researchers to develop bio-based materials over conventional polymers. Since most of the established bio-based polymeric materials demonstrate prominent sustainability, however, performance, cost, and durability limit their utilization in real-time applications. Additionally, a sustainable circular bioeconomy (CE) ensures SDGs deliver material production, where it ceases the linear approach from production to waste. Simultaneously, sustainable circular bio-economy promoted materials should exhibit the prominent properties to involve and substitute conventional materials. These interceptions can be resolved through state-of-the-art bio-vitrimeric materials that display durability/mechanical properties such as thermosets and processability/malleability such as thermoplastics. This article emphasizes the current need for vitrimers based on bio-derived chemicals; as well as to summarize the developed bio-based vitrimers (including reprocessing, recycling and self-healing properties) and their requirements for a sustainable circular economy in future prospects.

Self-Healing Silsesquioxane-Based Materials

This review is devoted to self-healing materials (SHM) containing polyhedral oligomeric silsesquioxanes (POSS) as building blocks. The synthetic approach can vary depending on the role POSS are expected to play in a given system. POSS (especially double-decker silsesquioxanes) can be grafted in side chains of a polymer backbone or used as segments of the main chain. Appropriate functionalization allows the formation of dynamic bonds with POSS molecules and makes them an active component of SHM, both as crosslinking agents and as factors that enhance the dynamics of macromolecules in the polymer matrix. The latter effect can be achieved by reversible release of bulky POSS cages or by the formation of separated inclusions in the polymer matrix through hydrophobic interactions and POSS aggregation. The unique properties of POSS-based self-healing systems make them interesting and versatile materials for various applications (e.g., repairable coatings, sealants, sensors, soft materials for tissue engineering, drug delivery, and wound healing).

Self-healing hydrophobic POSS-functionalized fluorinated copolymers via RAFT polymerization and dynamic Diels–Alder reaction

Development of self-healing hydrophobic POSS-functionalized fluorinated copolymethacrylate(s) via RAFT Polymerization and dynamic Diels–Alder Reaction.

Self-healing elastomers based on conjugated diolefins: a review

The introduction of dynamic covalent and physical crosslinks into diolefin-based elastomers improves mechanical and self-healing properties. The presence of dynamic crosslinks also helps in the reprocessing of elastomers.

Photoresponsive chain collapse in a flexo-rigid functional copolymer to modulate the self-healing behaviour

Synthetic systems mimicking the natural self-folding process are attractive to impart multiple structural control over polymer crosslinking and the subsequent alteration of their macroscopic self-healing properties. In that regard, polymers P1-P5 containing pendant photo-crosslinkable moieties were designed and underwent intra- or interchain collapse to form diverse nanostructures. The shape and dimension of the nanostructures could be efficiently controlled by the concentration, solvent compatibility and characteristics of the polymers. Photodimerization of the coumarin moieties transformed the extended coiled chain of the polymer to uniform sized nanoparticles in a dilute condition, while in the crowded macromolecular concentration regime, the polymer folded into nanostructures with polydisperse topologies that were far from a condensed globule or partially swollen globule conformation. Scaling law exponents for polymer chain compaction suggested an interchain collapse with rigid compact segments connected by flexible polymer chains that draws an analogy with elastomers. Such a hardening of the rigid segment as a consequence of photodimerization rendered a significant increase in the glass transition temperature (Tg), which could be reversibly controlled upon decrosslinking. Lastly, the structural variation of this class of polymers over self-healing was explored and the crosslinked polymers showed phototriggered non-autonomic and intrinsic self-healing behaviour under ambient conditions. This is an interesting approach to access a photomodulated self-healing system with low Tg polymers that shows the coexistence of autonomic and nonautonomic self-healing pathways and that may find application in designing smart coatings for photovoltaic devices.

Micromechanical and positron annihilation lifetime study of new cellulose esters with different topological structures

Two new groups of cellulose esters with a substituent, either trifluoromethylbenzoate or methylbenzoate, were synthesized in homogeneous conditions. The actual presence of aromatic substituents was demonstrated by ¹H-NMR spectra. The mechanical and structural peculiarities were determined by Depth Sensing Indentation (DSI) and Positron Annihilation Lifetime Spectroscopy (PALS) techniques. The relative position of CH₃ and CF₃ groups on the aromatic substituents influences the molecular packing differently and affects the formation of free volumes. The hardness characteristics and modulus of the corresponding cellulose esters were the lowest when the CH₃ and CF₃ groups are in m-position on the aromatic substituents. Meanwhile, they exhibited the highest number density of the free volume holes, as revealed by the o-Ps intensity values. An inverse linear relationship between the hardness, respectively on the modulus, and the o-Ps intensity was found. A simplified scheme of the structural feature of the investigated cellulose esters was proposed.

A new healable polymer material based on ultrafast Diels–Alder ‘click’ chemistry using triazolinedione and fluorescent anthracyl derivatives: a mechanistic approach

Development of a new healable polymer based on ultrafast Diels–Alder ‘click’ chemistry using fluorescent anthracyl and TAD derivatives. The ultrafast mechanistic approach is rationalized via Density Functional Theory (DFT) study.

Self-Healable Antifouling Zwitterionic Hydrogel Based on Synergistic Phototriggered Dynamic Disulfide Metathesis Reaction and Ionic Interaction

A self-healable antifouling hydrogel based on zwitterionic block copolymer was prepared via reversible addition-fragmentation chain transfer polymerization and Diels-Alder "click" chemistry. The hydrogel consists of a core-cross-linked zwitterionic block copolymer having poly(furfuryl methacrylate) as core and poly(dimethyl-[3-(2-methyl-acryloylamino)-propyl]-(3-sulfopropyl)ammonium) (poly(sulfobetaine)) as shell. The core was cross-linked with dithiobismaleimidoethane. The block copolymers were characterized by dynamic light scattering, field emission scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy (AFM), differential scanning calorimetry, water contact angle, and small-angle X-ray scattering analyses. This zwitterionic hydrogel showed self-healing activity via combined effect of phototriggered dynamic disulfide metathesis reaction and zwitterionic interaction, which was monitored by optical microscopy and AFM depth profilometry. The mechanical properties of the hydrogel before and after self-healing were studied using depth-sensing nanoindentation method. It was observed that the prepared zwitterionic hydrogel could reduce the formation of biofilm, which was established by studying the bovine serum albumin (model protein) adsorption over the coating. This multifunctional hydrogel can pave a new direction in antifouling self-healable gel coating applications.

Preparation and properties of self-healing polyether amines based on Diels–Alder reversible covalent bonds

Over time, automotive coating is bound to be damaged; therefore, it is necessary to give the coating a self-healing ability to make its performance even better. First, furfuryl glycidyl ether (FGE) was synthesized by epichlorohydrin and furfuryl alcohol. Then, furanyl-terminated resin FGE-T5000 was synthesized by polyether amine T5000 and FGE. Finally, 4,4′-diphenylmethane bismaleimide (BDM) was added to FGE-T5000 as a cross-linking agent to form a resin named FGE-T5000-BDM which has Diels–Alder (DA) bonds. The products were characterized by Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance, differential scanning calorimeter, dynamic mechanical analysis, thermogravimetric analysis, optical microscope, tensile tests, and other tests. The results showed that FGE-T5000-BDM demonstrated thermally reversible self-healing property from 50°C to 150°C, and that the best temperature of the DA reaction was 80°C. The gel content of FGE-T5000-BDM was 98%. Also, the glass transition temperature and the initial temperature of the Retro-DA (r-DA) reaction were −58°C and 88°C, respectively. Moreover, the self-healing efficiency of FGE-T5000-BDM was up to 88% after staying at 80°C for 12 h. The innovation shown in this article was that the reversible covalent bonds (DA) were combined with the polyether amines, which produced the characteristics of self-healing. Its unique self-healing properties are useful in some areas, such as automobile coatings and other materials.

Thermo-reversible self-healing in a fluorous crosslinked copolymer

Self-healing in a fluorous copolymer material enhances its safety index and extends its working lifetime.

The Taming of the Maleimide: Fabrication of Maleimide-Containing 'Clickable' Polymeric Materials

Functional polymers are widely employed in various areas of biomedical sciences. In order to tailor them for desired applications, facile and efficient functionalization of these polymeric materials under mild and benign conditions is important. Polymers containing reactive maleimide groups can be employed for such applications since they provide an excellent handle for conjugation of thiol- and diene-containing molecules and biomolecules. Until recently, fabrication of maleimide containing polymeric materials has been challenging due to the interference from the highly reactive double bond. A Diels-Alder/retro Diels-Alder reaction sequence based strategy to transiently mask the maleimide group provides access to such polymeric materials. In this personal account, we summarize contributions from our group towards the fabrication and functionalization of maleimide-containing polymeric materials over the past decade.

Exploring structural effects in single-chain “folding” mediated by intramolecular thermal Diels–Alder chemistry

We describe a method to fold single polymer chains into nanoparticles using simple thermal Diels–Alder (DA) chemistry.

RAFT polymerization to form stimuli-responsive polymers

Stimuli-responsive polymers respond to a variety of external stimuli, which include optical, electrical, thermal, mechanical, redox, pH, chemical, environmental and biological signals. This paper is concerned with the process of forming such polymers by RAFT polymerization.

Ambient temperature induced Diels–Alder crosslinked networks based on controlled methacrylate copolymers for enhanced thermoreversibility and self-healability

An effective thermoreversible crosslinked network fabricated at ambient temperature from a new, controlled methacrylate copolymer having reactive maleimide pendants and a trifunctional furan (TFu) exhibiting effective self-healability.

Amphiphilic functional block copolymers bearing a reactive furfuryl group via RAFT polymerization; reversible core cross-linked micelles via a Diels–Alder “click reaction”

Amphiphilic BCPs, PFMA-b-PPEGMA were prepared via RAFT polymerization. They were self-assembled into micelles in aqueous medium with a hydrophobic PFMA core and hydrophilic PPEGMA corona. Core cross-linked micelles were prepared via the DA reaction.

Highly transparent and self-healing films based on the dynamic Schiff base linkage

In this study, we report highly transparent self-healing films based on Schiff base linkages between DF-PEG and CS via a layer-by-layer technique.

Magnetic Fe3O4 nanoparticles supporting Macmillan with controlled shell structure as an efficient and reusable catalyst for asymmetric reaction

Magnetic nanoparticles grafted with chiral polymer brushes offer an effective way to bridge the gap between heterogeneous and homogeneous catalysis.

Toward organic electronics with properties inspired by biological tissue

The carbon framework common to both organic semiconductors and biological structures suggests that these two classes of materials should be easily integrated.

Direct functionalization of multi-walled carbon nanotubes (MWCNTs) via grafting of poly(furfuryl methacrylate) using Diels–Alder “click chemistry” and its thermoreversibility

This investigation reports a simple and single step functionalization of multi-walled carbon nanotubes (MWCNTs) based upon the Diels–Alder (DA) reaction with poly(furfuryl methacrylate) (PFMA).

Recent strategies to develop self-healable crosslinked polymeric networks

Autonomous self-healable crosslinked materials designed with built-in ability to repair physical damage and cracks can prevent catastrophic failure and thus extend the lifetime of materials.