Installation of Zwitterionic α-Amino Phosphonic Acid Moieties on Surfaces via a Kabachnik-Fields Post-Polymerization Modification

Magnetic Self-Healing Hydrogel from Difunctional Polymers Prepared via the Kabachnik-Fields Reaction

The development of high quality magnetic self-healing hydrogels containing well-dispersed magnetic nanoparticle has been a challenging procedure due to unavailable methods of facilely introducing groups that can efficiently stabilize these magnetic nanoparticles in the self-healing hydrogels. In this research, a polymer containing both phenylboronic acid (PBA) and phosphonic acid (PA) groups has been developed by the Kabachnik-Fields (KF) reaction. This polymer well disperses iron oxide nanoparticles (IONPs) through the strong interactions between the PA groups and the surface of the IONPs; thus, this polymer effectively mixed IONPs and poly(vinyl alcohol) (PVA) to form a hydrogel containing well-dispersed IONPs. The resulting hydrogel is self-healing, owing to the dynamic borate ester linkages. Moreover, the presence of the IONPs endowed the hydrogel with magnetic properties, also making it heat-responsive in an alternating magnetic field and expanding its application as a contrast agent for magnetic resonance imaging. The magnetic self-healing hydrogel showed excellent biosafety properties in animal experiments, suggesting its potential as an injectable implant material for biological and medical applications. This research exploits a biocompatible magnetic self-healing hydrogel with well-dispersed IONPs, demonstrating the value of the KF reaction in the development of functional polymers and smart materials, which might prompt a broad study of multicomponent reactions in interdisciplinary fields.

Stimuli-Responsive Multifunctional Phenylboronic Acid Polymers Via Multicomponent Reactions: From Synthesis to Application

Stimuli-responsive polymers undergo changes under different environmental conditions. Among them, phenylboronic acid (PBA) containing polymers (PBA-polymers) are unique, because they can selectively react with diols to generate borates that are sensitive to pH, sugars, and H₂ O₂ , and can be effectively used to synthesize smart drug carriers and self-healing hydrogels. Recently, multifunctional PBA-polymers (MF-PBA-polymers) have been developed using multicomponent reactions (MCRs) to introduce PBA groups into polymer structures. These MF-PBA-polymers have features similar to those of traditional PBA-polymers; moreover, they exhibit additional properties, such as fluorescence, antimicrobial activity, and antioxidant capability, when different MCRs are used. In this mini review, the preparation of these MF-PBA-polymers are summarized and the new properties/functions that have been introduced into these polymers using different MCRs are discussed. The uses of these MF-PBA-polymers as fluorescent cell anticoagulants, drug carriers, and gelators of functional self-healing hydrogels have been discussed. Additionally, the challenges encountered during their preparation are discussed and also the future developments in this field are touched upon.

Antioxidant Polymers via the Kabachnik-Fields Reaction to Control Cellular Oxidative Stress

Small molecular antioxidants are almost ineffective in regulating harmful oxidative stress in vivo because of their poor bioavailability. Polymer antioxidants are a promising alternative to address this issue, but their laborious synthetic routes limit their development. In this study, aliphatic and aromatic aldehydes are used to synthesize a family of polymers containing different α-aminophosphonate pendant groups via a facile one-pot method that combines the Kabachnik-Fields (KF) reaction and free radical polymerization. The structure-property relationship study of these polymers reveals the KF moieties in polymer structures confer radical scavenging ability on polymers. The radical scavenging ability and cytotoxicity of these polymers are evaluated in a stepwise manner to identify a biocompatible polymer antioxidant that can effectively protect the cells from H₂ O₂ -induced oxidative damage. This is the first attempt to develop antioxidative polymers by the KF reaction. It highlights the feasibility of synthesizing new functional polymers using multicomponent reactions, which has important implications for organic and polymer chemistry.

Post-polymerization modification via the Biginelli reaction to prepare water-soluble polymer adhesives

A copolymer precursor containing the β-ketoester moiety has been modified through the Biginelli reaction to get several water-soluble adhesives which are comparable to commercial glues.

Synthesis of Polymers via Kabachnik-Fields Polycondensation

Kabachnik-Fields reaction was employed as a new method for polycondensation. For this purpose, polymers were prepared from a mixture of dialdehydes, diamines, and phosphites. Variation of different starting monomers allowed the synthesis of polymers with tunable properties. It not only allowed the variation of glass transition temperatures but also enabled the synthesis of highly functional polymers including zwitterionic polymers. Further, photodegradable polymers have been realized by utilizing a photolabile dialdehyde monomer, which renders the obtained polymers highly interesting for numerous applications.

Multicomponent Copolycondensates via the Simultaneous Hantzsch and Biginelli Reactions

The tricomponent Biginelli reaction and the tetracomponent Hantzsch reaction which share the same reaction modules (aldehyde and β-ketone ester) have been found compatible. Therefore, a series of copolycondensates containing both 1,4-dihydropyridine (1,4-DHP) and 3,4-dihydropyrimidin-2(1H)-one (3,4-DHPM) in the main chains via the simultaneous Hantzsch and Biginelli reactions have been facilely synthesized. The ratio of 1,4-DHP and 3,4-DHPM in the polymer congeners could be easily tuned by changing the feeding ratio of reactants, and the thermal properties of the obtained polymers are thereby adjusted. As the first attempt to prepare copolycondensate through the combination of two multicomponent reactions (MCRs), the current method revealed and utilized the interesting compatibility between MCRs, providing a new strategy to prepare multicomponent functional polymers.

Versatile side chain modification via isocyanide-based multicomponent reactions: tuning the LCST of poly(2-oxazoline)s

Poly(2-oxazoline)s are receiving large current interest based on their potential use in biomedical applications. Here we report a novel, straightforward route towards functional poly(2-oxazoline)s by Passerini and Ugi reactions.