Synthesis of Optically and Redox Active Polyenaminones from Diamines and α,α'-Bis[(dimethylamino)methylidene]cyclohexanediones

New oligo- and polyenaminones with M_w ~ 7-50 KDa were prepared in high yields by transaminative amino-enaminone polymerization of regioisomeric bis[(dimethylamino)methylidene]cyclohexanediones with alkylene and phenylenediamines. The polymers obtained are practically insoluble in aqueous and organic solvents and exhibit film-forming properties, UV light absorption at wavelengths below 500 nm, and redox activity. These properties indicate a promising application potential of these polymers, which could find use in optical and optoelectronic applications and in energy storage devices.

Multicomponent Polymerization for π-Conjugated Polymers

Structurally complex π-conjugated polymers hold great promise as key components in sensor and electronic devices; however, their syntheses have not been a trivial task. From a synthetic efficiency perspective, it would be more attractive to access these materials using convenient and efficient methods from simple building blocks. One such synthetic tool, multicomponent polymerization, can accommodate modularity and provide highly efficient syntheses. This feature article outlines several multicomponent polymerization strategies for the synthesis of various π-conjugated polymers, which are classified based upon how the monomers are aligned during polymerization. Additionally, the challenges and outlooks of this field are highlighted and discussed.

One-Step Multicomponent Polymerizations for the Synthesis of Multifunctional AIE Polymers

As a new class of functional luminescent materials, polymers with aggregation-induced emission (AIE) feature attract much attention because of their advantages of efficient solid-state fluorescence, excellent processability, structural diversity, and multifunctionalities. Among all polymerization methods toward AIE polymers, multicomponent polymerizations (MCPs) exhibit the merits of simple operation, good atom economy, high polymerization efficiency, broad functional-group tolerance, etc. In this feature article, the recent progress on the development of one-step MCPs for the synthesis of AIE polymers is highlighted. The representative functionalities of the resulting AIE polymers are illustrated. Perspectives on the challenges and future development directions of this field are also discussed.

Elastomeric polyamide biomaterials with stereochemically tuneable mechanical properties and shape memory

Biocompatible polymers are widely used in tissue engineering and biomedical device applications. However, few biomaterials are suitable for use as long-term implants and these examples usually possess limited property scope, can be difficult to process, and are non-responsive to external stimuli. Here, we report a class of easily processable polyamides with stereocontrolled mechanical properties and high-fidelity shape memory behaviour. We synthesise these materials using the efficient nucleophilic thiol-yne reaction between a dipropiolamide and dithiol to yield an α,β - unsaturated carbonyl moiety along the polymer backbone. By rationally exploiting reaction conditions, the alkene stereochemistry is modulated between 35-82% cis content and the stereochemistry dictates the bulk material properties such as tensile strength, modulus, and glass transition. Further access to materials possessing a broader range of thermal and mechanical properties is accomplished by polymerising a variety of commercially available dithiols with the dipropiolamide monomer.

Functional Poly(dihalopentadiene)s: Stereoselective Synthesis, Aggregation-Enhanced Emission and Sensitive Detection of Explosives

The development of polymeric materials with novel structures and unique properties and functionalities is of both academic and industrial significance. In this work, functional poly(dihalopentadiene)s were synthesized by boron trihalide-mediated multicomponent polymerization routes in a stereoselective manner. The polymerizations of tetraphenylethylene-containing diyne, BX₃ (X = Cl, Br) and p-tolualdehyde proceed smoothly in dichloromethane under mild conditions to afford high molecular weight poly(dihalopentadiene)s with a predominant (Z,Z)-configuration in moderate to good yields. The reaction conditions and the boron trihalide used were found to have great effects on the stereochemistry of the resulting polymer structures. The obtained poly(1,5-dihalo-(Z,Z)-1,4-pentadiene)s possess high thermal stability and good film-forming ability. Their thin films show high refractive index of 1.9007⁻1.6462 in a wide wavelength region of 380⁻890 nm with low optical dispersion. The polymers are weakly emissive in dilute solutions but become highly emissive upon aggregated, demonstrating a unique phenomenon of aggregation-enhanced emission. Their nanoaggregates in aqueous media can serve as sensitive fluorescent chemosensors for the detection of explosives with a superamplification effect and a low detection limit.

Injectable and Degradable pH-Responsive Hydrogels via Spontaneous Amino-Yne Click Reaction

Injectable hydrogels have attracted increasing attention in tissue regeneration and local drug delivery applications. Current click reactions for preparing injectable hydrogels often require a photoinitiator or catalyst, which may be toxic and may involve complex synthesis of precursors. Here, we report a facile and inexpensive method to prepare injectable and degradable hydrogels via spontaneous amino-yne click reaction without using any initiator or catalyst under physiological conditions based on telechelic electron-deficient dipropiolate ester of polyethylene glycol and water-soluble commercially available carboxymethyl chitosan (CMC). The gelation time, mechanical property, and degradation rate of the hydrogels could be adjusted by varying CMC concentrations and stoichiometric ratios. The reversible pH-induced sol-gel transitions of the hydrogel are presented and the pH-controlled drug release behaviors are demonstrated, of which the mechanism is discussed. In vitro cytotoxicity assays and in vivo in situ injection study of the CMC-based hydrogels showed favorable gel formation, nontoxicity, and good tissue biocompatibility. Therefore, these biodegradable and injectable hydrogels prepared by spontaneous amino-yne click reaction hold potential for tissue engineering and other biomedical applications.

Ultrafast and efficient aza- and thiol-Michael reactions on a polyester scaffold with internal electron deficient triple bonds

A polyester scaffold possessing electron deficient triple bonds in the main chain was prepared and utilized as a precursor for aza- and thiol-Michael addition reactions.

Polyurethanes with aggregation-enhanced emission characteristics: preparation and properties

An amino-terminated poly(propylene glycol)-modified tetraaryl-buta-1,3-diene derivative (TABDAA) was introduced to synthesize polyurethanes with different ratios of soft/hard segments. A mixture of TABDAA and poly(tetrahydrofuran) 1000 as the soft segments was reacted with 4,4-diphenylmethane diisocyanate and 1,4-butanediol as the hard segments in molar ratios of 1 : 2 : 1, 2 : 3 : 1, and 3 : 4 : 1 to give the desired polyurethanes named TMPU-211, TMPU-321 and TMPU-431, respectively. The three polyurethanes exhibited different aggregation-enhanced emission (AEE) behaviors because of their different soft/hard segment ratios. The polyurethanes with a higher soft segment content tended to form bigger particles in a DMF/water mixture solution, thus causing a sharper increase in their fluorescence intensity. In addition, the polyurethane films exhibited different fluorescence intensities after different heat treatments. After a quenching treatment of the soft segments in the polyurethane films, the fluorescence intensity dropped greatly. When these quenched polyurethane films were thermally annealed at 60 °C for 24 hours, their fluorescence intensity exceeded the initial intensity of the as-prepared films. Differential scanning calorimetry results showed that the polyurethane films in the quenched condition did not present the endothermal melting peak of the soft segments, and the melting peaks appeared again after thermal annealing. AFM experiments showed that an ordered arrangement was achieved after the heat treatment of these AEE polyurethane films. These results demonstrated that the polymer structure had a significant effect on the AEE properties of the polyurethane films, and more importantly, it is of great significance in improving the fluorescence emission of the AEE polymers and also for their potential application in fluorescent probes, stimuli-responsive materials, PLED devices and so on.

Synthesis of enaminones via copper-catalyzed decarboxylative coupling reaction under redox-neutral conditions

A novel copper-catalyzed C(sp³)–H oxidative functionalization of oxime acetates for the synthesis of enaminones under redox-neutral conditions has been developed.

Metal-Free, Multicomponent Synthesis of Pyrrole-Based π-Conjugated Polymers from Imines, Acid Chlorides, and Alkynes

Multicomponent coupling reactions (MCRs) are becoming increasingly used in the synthesis of macromolecules, as they can allow the rapid generation of libraries of materials as a method to tune properties. MCRs could prove particularly useful in the synthesis of π-conjugated polymers in which structural changes are necessary for fine-tuning of electronic properties. We describe here the first metal-free multicomponent approach to conjugated polymers. This reaction exploits the coupling of imines, acid chlorides, and (catechyl)PPh to generate phospha-münchnone-containing polymers, which can be converted to poly(pyrroles) via cycloaddition. The platform allows for the efficient synthesis of families of high molecular weight polymers in one step from readily available monomers.

Multicomponent polymerization: development of a one-pot synthetic route to functional polymers using diyne, N-sulfonyl azide and water/ethanol as reactants

Multicomponent polymerization: a one-pot synthetic route toward luminescent polymers.

Multicomponent sequential polymerizations of alkynes, carbonyl chloride and amino ester salts toward helical and luminescent polymers

Sequential coupling-hydroamination polymerizations toward helical and luminescent polymers.

BCl3-mediated polycoupling of alkynes and aldehydes: a facile, metal-free multicomponent polymerization route to construct stereoregular functional polymers

BCl₃-mediated alkyne–aldehyde polymerization to stereoregular functional polymers in a facile, metal-free and multicomponent manner.

Cu(i)-Catalyzed amino-yne click polymerization

The first example of Cu(i)-catalyzed regio-specific and stereo-selective amino-yne click polymerization was established.

Regio- and stereoselective construction of stimuli-responsive macromolecules by a sequential coupling-hydroamination polymerization route

Sequential coupling-hydroamination polymerization towards stimuli-responsive polymers.