Self-healing nanocomposites from silica − polymer core − shell nanoparticles

Induction heating induced self-healing of nanocomposites based on surface-functionalized cationic iron oxide particles and polyelectrolytes

Supramolecular interactions represent versatile, reversible, and intrinsic mechanisms for bond formation after the failure of materials. Ionic interactions excel through high flexibility and binding strength. In this study, ionic interactions between polymer matrices and inorganic nanoparticles were used to induce self-healing properties. Random, anionic polyelectrolyte copolymers consisting of di(ethylene glycol) methyl ether methacrylate and sodium-4-(methacryloyloxy)butan-1-sulfonate were synthesized by atom transfer radical polymerization. Differential scanning calorimetry measurements confirmed the adjustability of the glass transition temperature via the polymer composition. Within the glass transition temperature window of the homopolymers from -23 °C to 126 °C, the range between -18 °C to 50 °C was examined, generating suitable matrices for self-healing. Superparamagnetic iron oxide nanoparticles with a size of 8 nm were synthesized by thermal decomposition of iron(iii) acetylacetonate and used as the inorganic filler. Positive surface charges were introduced by functionalization with N,N,N-trimethyl-6-phosphonhexan-1-aminium bromide. Functionalization was confirmed with FTIR, TGA, and zeta potential measurements. Ionic interactions between filler and polymer promote a uniform particle dispersion within the material. Self-healing experiments were performed at 80 °C and without the addition of further healing agents. Utilizing the magnetic properties induced by the iron oxide nanoparticles, spatially resolved healing within an alternating magnetic field was achieved on a μm scale.

Influence of the Glass Transition Temperature and the Density of Crosslinking Groups on the Reversibility of Diels-Alder Polymer Networks

The interest in self-healing, recyclable, and adaptable polymers is growing. This work addresses the reversibility of crosslink formation based on Diels-Alder reaction in copolymer networks containing furfuryl and maleimide groups, which represent the "diene" and the "dienophile," respectively. The copolymers are synthesized by atom transfer radical polymerization (ATRP) and free radical polymerization. The diene bearing copolymers are crosslinked either with a small molecule containing two dienophiles or with a dienophile bearing copolymer. The influence of the crosslinking temperature on the Diels-Alder reaction is analyzed. Furthermore, the influence of the glass transition temperature and the influence of the density of crosslinking groups on the thermo-reversibility of crosslinking are investigated by temperature dependent infrared spectroscopy and differential scanning calorimetry. It is shown that the reversibility of crosslinking is strongly influenced by the glass transition temperature of the system.

Synthesis and characterisation of biocompatible organic-inorganic core-shell nanocomposite particles based on ureasils

Organic-inorganic core-shell nanocomposites have attracted increasing attention for applications in imaging, controlled release, biomedical scaffolds and self-healing materials. While tunable properties can readily be achieved through the selection of complementary building blocks, synergistic enhancement requires management of the core-shell interface. In this work, we report a one-pot method to fabricate hybrid core-shell nanocomposite particles (CSNPs) based on ureasils. The native structure of ureasils, which are poly(oxyalkylene)/siloxane hybrids, affords formation of an organic polymer core via nanoprecipitation, while the terminal siloxane groups act as a template for nucleation and growth of the silica shell via the Stöber process. Through optimisation of the reaction conditions, we demonstrate the reproducible synthesis of ureasil CSNPs, with a hydrodynamic diameter of ∼150 nm and polydispersity <0.2, which remain electrostatically stabilised in aqueous media for >50 days. Selective functionalisation, either through the physical entrapment of polarity-sensitive fluorescent probes (coumarin 153, pyrene) or covalent-grafting to the silica shell (fluorescein isothiocyanate) is also demonstrated and provides insight into the internal environment of the particles. Moreover, preliminary studies using a live/dead cell assay indicate that ureasil CSNPs do not display cytotoxicity. Given the simple fabrication method and the structural tunability and biocompatability of the ureasils, this approach presents an efficient route to multifunctional core-shell nanocomposite particles whose properties may be tailored for a targeted application.

Advances in intrinsic self-healing polyurethanes and related composites

Fascinating and challenging, the development of repairable materials with long-lasting, sustainable and high-performance properties is a key-parameter to provide new advanced materials. To date, the concept of self-healing includes capsule-based healing systems, vascular healing systems, and intrinsic healing systems. Polyurethanes have emerged as a promising class of polymeric materials in this context due to their ease of synthesis and their outstanding properties. This review thereby focuses on the current research and developments in intrinsic self-healing polyurethanes and related composites. The chronological development of such advanced materials as well as the different strategies employed to confer living-like healing properties are discussed. Particular attention will be paid on chemical reactions utilized for self-healing purposes. Potential applications, challenges and future prospects in self-healing polyurethane fields are also provided.

Mechanically and thermo-driven self-healing polyurethane elastomeric composites using inorganic–organic hybrid material as crosslinker

Self-healable, recyclable, and robust polyurethane elastomeric composites by thermally driven Diels–Alder chemistry using inorganic–organic hybrid material as crosslinker.

Advances in self-healing supramolecular soft materials and nanocomposites

The ability to rationally tune and add new end-groups in polymers can lead to transformative advances in emerging self-healing materials. Self-healing networks manipulated by supramolecular strategies such as hydrogen bonding and metal coordination have received significant attention in recent years because of their ability to extend materials lifetime, improve safety and ensure sustainability. This review describes the recent advancements in supramolecular polymers self-healing networks based on hydrogen bonding, metal-containing polymers and their nanocomposites. Collectively, the aim of this review is to provide a panoramic overview of the conceptual framework for the interesting nexus between hydrogen bonding and metal-ligand interactions for enabling supramolecular self-healing soft materials networks and nanocomposites. In addition, insights on the current challenges and future perspectives of this field to propel the development of self-healing materials will be provided.

Polymer Nanocomposites via Click Chemistry Reactions

The emerging areas of polymer nanocomposites, as some are already in use in industrial applications and daily commodities, have the potential of offering new technologies with all manner of prominent capabilities. The incorporation of nanomaterials into polymeric matrix provides significant improvements, such as higher mechanical, thermal or electrical properties. In these materials, interface/interphase of components play a crucial role bringing additional features on the resulting nanocomposites. Among the various preparation strategies of such materials, an appealing strategy relies on the use of click chemistry concept as a multi-purpose toolbox for both fabrication and modulation of the material characteristics. This review aims to deliver new insights to the researchers of the field by noticing effective click chemistry-based methodologies on the preparation of polymer nanocomposites and their key applications such as optic, biomedical, coatings and sensor.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Monodisperse core–shell melamine–formaldehyde polymer-modified silica microspheres prepared using a facile microwave-assisted method

A facile microwave-assisted synthesis method for the preparation of monodisperse core–shell melamine–formaldehyde (MF)-modified silica resin microspheres (SiO₂@MF) was developed.