Click Polymerization Research Articles

Preparation of silk fibroin/hyaluronic acid composite hydrogel based on thiol-ene click chemistry.

To design and prepare silk fibroin/hyaluronic acid composite hydrogel. The thiol modified silk fibroin and the double-bond modified hyaluronic acid were rapidly cured into gels through thiol-ene click polymerization under ultraviolet light condition. The grafting rate of modified silk fibroin and hyaluronic acid was characterized by 1H NMR spectroscopy; the gel point and the internal microstructure of hydrogels were characterized by rheological test and scanning electron microscopy; the mechanical properties were characterized by compression test; the swelling rate and degradation rate were determined by mass method. The hydrogel was co-cultured with the cells, the cytotoxicity was measured by the lactate dehydrogenase method, the cell adhesion was measured by the float count method, and the cell growth and differentiation on the surface of the gel were observed by scanning electron microscope and fluorescence microscope. The functional group substitution degrees of modified silk fibroin and hyaluronic acid were 17.99% and 48.03%, respectively. The prepared silk fibroin/hyaluronic acid composite hydrogel had a gel point of 40-60 s and had a porous structure inside the gel. The compressive strength was as high as 450 kPa and it would not break after ten cycles. The water absorption capacity of the composite hydrogel was 4-10 times of its own weight. Degradation experiments showed that the hydrogel was biodegradable, and the degradation rate reached 28%-42% after 35 d. The cell biology experiments showed that the cytotoxicity of the composite gel was low, the cell adhesion was good, and the growth and differentiation of the cells on the surface of the gel were good. The photocurable silk fibroin/hyaluronic acid composite hydrogel can form a gel quickly, and has excellent mechanical properties, adjustable swelling rate and degradation degree, good biocompatibility, so it has promising application prospects in biomedicine.

X‐yne click polymerization

AbstractAlkyne‐based click polymerizations have been nurtured into a powerful synthetic technique for the preparation of new polymers with advanced structures and versatile properties. Among them, the emerging thiol‐yne, hydroxyl‐yne, and amino‐yne click polymerizations have made remarkable progress from reactions to applications. These polymerizations avoid the usage of inherently dangerous monomers and are safer to operate than the classical azide‐alkyne click polymerization (AACP), making them more prospective for diverse applications. To greatly promote the new alkyne‐based click polymerizations beyond AACP, a new concept of “X‐yne click polymerization” is proposed to unify them, where “X” denotes the monomers that can react with alkynes under mild reaction conditions, including thiols, alcohols, amines, and other promising ones. In this review, we mainly present a brief account of the progress of X‐yne click polymerization and discuss in detail the challenges and opportunities in this field.

Tailor-made poly(vinylidene sulfide)s by Rh(I)–NHC catalyzed regioselective thiol-yne click polymerization

The [Rh(μ-Cl)(IPr)(η2-coe)]2/pyridine system efficiently catalyzes the polyhydrothiolation of a series of dialkynes with dithiols, producing sulfur-rich poly(vinylidene sulfide)s with a typical Mw in the range 20.000–124.000 and vinylidene content of 75–87%. A combination of flexible aliphatic dithiols, including 1,6-hexanedithiol and 2,2′-(ethylendioxy)diethanethiol, and the rigid aromatic dithiol 4,4′-thiobisbenzenethiol, with rigid aromatic dialkynes, 1,3-diethynylbenzene and 1,4-diethynylbenzene, and flexible dialkynes, including propargyl ether and 1,7-octadiyne, have been used to prepare poly(vinylidene sulfide)s. The copolymerization of flexible dithiols with rigid aromatic dialkynes or vice versa results in high molecular weight polymers, Mw up to 259.000, with low polydispersities. However, polyhidrothiolation of flexible dialkynes with flexible dithiols is much less efficient and usually results in the formation of oligomers. The interplay of the IPr and pyridine ligands on the RhCl(IPr)(py)(η2-coe) catalyst, which controls the regioselectivity of the alkyne insertion step towards the branched vinyl sulfide, is key in the preparation of these poly(vinylidene sulfide)s.

Charge-conversional click polyprodrug nanomedicine for targeted and synergistic cancer therapy.

Polyprodrug nanomedicines hold great potential for combating tumors. However, the functionalization of polyprodrug nanomedicines to improve therapeutic efficacy is restricted by conventional polymerization methods. Herein, we fabricated a charge-conversional click polyprodrug nanomedicine system by metal-free azide-alkyne cycloaddition click polymerization (AACCP) for targeted and synergistic cancer therapy. Specifically, Pt(IV) prodrug-backboned diazide monomer, DMC prodrug-pendent diazide monomer, dialkyne-terminated PEG monomer and azide-modified folate were click polymerized to obtain the target polyprodrug (P1). P1 could self-assemble into nano-micelles (1-NM), where PEG was the hydrophilic shell with folate on the surface, Pt(IV) and DMC prodrugs as the hydrophobic core. Taking advantage of PEGylation and folate-mediated tumor cell targeting, 1-NM achieved prolonged blood circulation time and high tumor accumulation efficiency. Tumor acidic microenvironment-responsive cleavage and cascade activation of pendant DMC prodrug induced surface charge conversion of 1-NM from negative to positive, which promoted tumor penetration and cellular internalization of the remaining 1-NM. After internalization into tumor cells, the reduction-responsive activation of Pt(IV) prodrug to Pt(II) further showed synergetic effect with DMC for enhanced apoptosis. This first designed charge-conversional click polyprodrug nanomedicine exhibited targeted and synergistic efficacy to suppress tumor proliferation in living mice bearing human ovarian tumor model.

In Situ Synthesis of AIEgen-based Porous Organic Polymer Films by Interfacial Amino-yne Click Polymerization for Efficient Light-Harvesting.

We developed a catalyst-free, atom-economical interfacial amino-yne click polymerization to in situ synthesize new aggregation-induced emission luminogen (AIEgen)-based free-standing porous organic polymer films at room temperature. The crystalline properties of POP films were confirmed by powder X-ray diffraction and high-resolution transmission electron microscopy. The good porosity of these POP films was proved by their N2 uptake experiments. The thickness of POP films can be easily regulated from 16 nm to ≈1 μm by adjusting monomer concentration. More importantly, these AIEgen-based POP films show bright luminescence with high absolute photoluminescent quantum yields up to 37.8 % and good chemical and thermal stability. The AIEgen-based POP film can encapsulate an organic dye (e.g., Nile red) to further form an artificial light-harvesting system with a large red-shift (Δλ=141 nm), highly efficient energy-transfer ability (ΦET =91 %), and high antenna effect (11.3).

In Situ Synthesis of AIEgen‐based Porous Organic Polymer Films by Interfacial Amino‐yne Click Polymerization for Efficient Light‐Harvesting

AbstractWe developed a catalyst‐free, atom‐economical interfacial amino‐yne click polymerization to in situ synthesize new aggregation‐induced emission luminogen (AIEgen)‐based free‐standing porous organic polymer films at room temperature. The crystalline properties of POP films were confirmed by powder X‐ray diffraction and high‐resolution transmission electron microscopy. The good porosity of these POP films was proved by their N2 uptake experiments. The thickness of POP films can be easily regulated from 16 nm to ≈1 μm by adjusting monomer concentration. More importantly, these AIEgen‐based POP films show bright luminescence with high absolute photoluminescent quantum yields up to 37.8 % and good chemical and thermal stability. The AIEgen‐based POP film can encapsulate an organic dye (e.g., Nile red) to further form an artificial light‐harvesting system with a large red‐shift (Δλ=141 nm), highly efficient energy‐transfer ability (ΦET=91 %), and high antenna effect (11.3).

Truxene-Based Porous Triazole-Linked Polymers for Dye Removal through Synergetic Adsorption and Photodegradation

Two high surface area porous polymers (TxTri and PhTxTri) consisting of semiconducting truxene units connected through triazole nodes have been synthesized via Cu(I)-catalyzed azide–alkyne click polymerization, and their ability to remove different organic dyes (Nile blue, Rhodamine B, and Methyl orange) from aqueous solutions has been investigated. The presence of triazole moieties in the polymer walls, capable of binding guest molecules through different intermolecular interactions (such as dipole–dipole interactions, hydrogen bonding, and π–π interactions), is expected to benefit dye capture. We have found that these materials show a high adsorption capacity toward cationic dyes (reaching values as high as 1562 mg g–1 for Nile blue). This preference is probably due to the high electron density of the polymeric networks, which will favor electrostatic interactions with electron-deficient dyes. Interestingly, owing to the semiconducting nature of the truxene units, these polymers also act as photocatalysts in the oxidative degradation of the dyes, allowing for easy recovery and reuse of the polymers without the need for additional cleaning steps to remove trapped dyes. This interesting adsorption/photodegradation synergy represents a huge advantage compared to common dye adsorbents and makes them promising candidates for water remediation.

Monomeric and Polymeric Mesoionic N-Heterocyclic Carbene-Tethered Silver Nanoparticles: Synthesis, Stability, and Catalytic Activity.

In recent years, N-heterocyclic carbenes (NHCs) have garnered significant attention as promising alternatives to thiols to stabilize metallic nanoparticles and planar surfaces. While most studies thus far have focused on NHC-functionalized gold nanoparticles (AuNPs), as an ideal platform to investigate the role of NHCs in stabilizing such nanoparticles, their ability to protect more unstable coinage metal nanoparticles, such as silver nanoparticles (AgNPs), has been largely overlooked. This is despite the fact that AgNPs possess a much more sensitive optical response that, upon their enhanced stability, can broaden their scope of application in various fields, including nanomedicine and catalysis. In this study, the synthesis and use of monomeric and polymeric mesoionic NHC-Ag(I) complexes as precursors to mono- and multidentate NHC-tethered AgNPs are reported. The polymeric analog was obtained by first synthesizing a polymer, containing 1,2,3-triazole repeat units, employing the copper-catalyzed alkyne-azide cycloaddition click polymerization of monomers containing diazide- and dialkyne functional groups. Subsequent quaternization of the triazole moieties and Ag insertion yielded the target NHC-Ag-containing polymer. Using this polymer as well as its monomeric analog as substrates, AgNPs with either catenated networks of NHCs or monomeric NHCs were fabricated by their reduction using borane-tert-butylamine complex. Our stability studies demonstrate that while monomeric NHCs impart some degree of stability to AgNPs, particularly at elevated temperatures in aqueous as well as organic medium, their polymeric analogs further enhance their stability in acidic environment (pH = 2) and against glutathione (3 mM), as an example of a biologically relevant thiol, in aqueous media. To highlight the application of these NHC-functionalized AgNPs in catalysis, we explore the aqueous phase reduction of methyl orange and 4-nitrophenol.

Mechanism‐Guided Design of Chain‐Growth Click Polymerization Based on a Thiol‐Michael Reaction

AbstractThe development of chain‐growth click polymerization is challenging yet desirable in modern polymer chemistry. In this work, we reported a novel chain‐growth click polymerization based on the thiol‐Michael reaction. This polymerization could be performed efficiently under ambient conditions and spatiotemporally regulated by ultraviolet light, allowing the synthesis of sulfur‐containing polymers in excellent yields and high molecular weights. Density functional theory calculations indicated that the thiolate addition to the Michael acceptor is the rate‐determining step, and introducing the phenyl group could facilitate the chain‐growth process. This polymerization is a new type of chain‐growth click polymerization, which will provide a unique approach to creating functional polymers.

Mechanism-Guided Design of Chain-Growth Click Polymerization Based on a Thiol-Michael Reaction.

The development of chain-growth click polymerization is challenging yet desirable in modern polymer chemistry. In this work, we reported a novel chain-growth click polymerization based on the thiol-Michael reaction. This polymerization could be performed efficiently under ambient conditions and spatiotemporally regulated by ultraviolet light, allowing the synthesis of sulfur-containing polymers in excellent yields and high molecular weights. Density functional theory calculations indicated that the thiolate addition to the Michael acceptor is the rate-determining step, and introducing the phenyl group could facilitate the chain-growth process. This polymerization is a new type of chain-growth click polymerization, which will provide a unique approach to creating functional polymers.

Synthesis and characterization of poly(1,2,3‐triazole)s with inherent high sulfur content for optical applications

AbstractThe synthesis of solution‐processable sulfur‐containing polytriazoles for optoelectronic applications is a relatively less explored domain in polymer research. The synthesis of novel bifunctional (DA) and trifunctional (TA) azido‐monomers with inherent high sulfur content and of organo‐soluble high refractive index poly(1,2,3‐triazole)s using the azido‐monomers via Cu(I) assisted click polymerization reactions are reported in this work. The azido‐monomers were synthesized by the conversion of previously reported amine‐functionalized compounds to azides using azidotrimethylsilane in a polar aprotic solvent. Dialkyne monomers were also synthesized and reacted with the azides to prepare a series of five linear and two hyperbranched poly(1,2,3‐triazole)s. Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, differential scanning calorimetry and thermogravimetric analysis were used to characterize the synthesized polymers. It was also demonstrated that the use of the trifunctional azide in optimized conditions resulted in increased solubility of an otherwise insoluble linear poly(1,2,3‐triazole). The optical characterization of the polymers was carried out on thin polymer films with thickness in the nanometer range, which were successfully prepared by spin‐coating on silicon wafers. It was found that the increase in the sulfur and aromatic content in the polymer backbone successfully increased the refractive index of the polymers up to 1.743 at 589 nm.

Efficient adsorption of trinitrotoluene by isoxazoline‐based porous polymers prepared from room‐temperature stable bis(nitrile oxide)

AbstractA novel isoxazoline‐based porous adsorbent (PB‐TTNO) is prepared by click polymerization and freeze‐drying from a methyl‐containing bis(nitrile oxide) stable at room temperature. The introduction of four methyl groups around the nitrile oxide group reduces the activity of the bis(nitrile oxide) and make it react more mildly with polybutadiene, resulting in PB‐TTNO with a more uniform pore size. Meanwhile, the electron‐donating methyl groups further increase the π–π interaction between the polymer benzene ring and the TNT benzene ring. The π–π interaction enables one benzene ring in the polymer to interact with two TNT molecules to form a sandwich structure, which further improves the adsorption capacity. The synergistic effect of dual π–π interactions and dipole‐π interactions makes the maximum adsorption capacity of PB‐TTNO reach 235.3 mg g−1 within 12 h at 25°C. The factors such as pH value, adsorbent dosage, contact time, initial TNT concentration, and temperature are also discussed. The adsorption kinetics fit well with the pseudo‐second‐order model, and the Langmuir model exhibits better correlation for equilibrium data analysis. In addition, the adsorption data of PB‐TTNO in real water samples are similar to those in laboratory, and the maximum adsorption capacity decreases by only 15% after five adsorption–desorption cycles.

Synthesis of Degradable Polysulfamides via Sulfur(VI) Fluoride Exchange Click Polymerization of AB-Type Monomers.

Polysulfamides are the -SO2- analogues of polyureas and form an intriguing family of polymers containing hydrogen-bond donor and acceptor groups. However, unlike polyureas, their physical properties are mostly unknown because of the scarcity of synthetic methods to access such polymers. Herein, we report an expedient synthesis of AB monomers for the synthesis of polysulfamides via Sulfur(VI) Fluoride Exchange (SuFEx) click polymerization. Upon optimization of the step-growth process, a variety of polysulfamides were isolated and characterized. The versatility of the SuFEx polymerization allowed structural modulation of the main chain through the incorporation of aliphatic or aromatic amines. While all synthesized polymers presented high thermal stability via thermogravimetric analysis, the glass-transition temperature and crystallinity were shown to be highly tied to the structure of the backbone between repeating sulfamide units through differential scanning calorimetry and powder X-ray diffraction. Careful analysis via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and X-ray crystallography also revealed the formation of macrocyclic oligomers during the polymerization of one AB monomer. Finally, two protocols were developed to efficiently degrade all synthesized polysulfamides through either chemical recycling for polymers derived from aromatic amines or oxidative upcycling for those based on aliphatic amines.

Construction of Fluorescent Conjugated Polytriazole Containing Double-Decker Silsesquioxane: Click Polymerization and Thermal Stability.

This study synthesized two azide-functionalized monomers through p-dichloro xylene and double-decker silsesquioxane (DDSQ) units with NaN3 to form DB-N3 and DDSQ-N3 monomers, respectively. In addition, five different propargyl-functionalized monomers were also prepared from hydroquinone, bisphenol A, bis(4-hydroxyphenyl)methanone, 2,4-dihydroxybenzaldehyde (then reacted with hydrazine hydrate solution) and 1,2-bis(4-hydroxyphenyl)-1,2-diphenylethene with propargyl bromide to form P-B, P-BPA, P-CO, P-NP, and P-TPE monomers, respectively. As a result, various DDSQ-based main chain copolymers could be synthesized using Cu(I)-catalyzed click polymerization through DDSQ-N3 with different propargyl-functionalized monomers, of which the chemical structure and molecular weight could be confirmed by using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) analyses. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy analyses also could characterize the thermal stability, morphology, and optical behaviors of these DDSQ-based copolymers. All results indicate that the incorporation of an inorganic DDSQ cage could improve the thermal stability such as thermal decomposition temperature and char yield, because of the DDSQ dispersion homogeneously in the copolymer matrix, and this would then affect the optical properties of NP and TPE units in this work.

Acid-base responsive multifunctional poly(formyl sulfide)s through a facile catalyst-free click polymerization of aldehyde-activated internal diynes and dithiols.

Acid-base equilibria play a critical role in biological processes and environmental systems. The development of innovative fluorescent polymeric materials to monitor acid-base equilibria is highly desirable. Herein, a novel catalyst-free click polymerization of aldehyde-activated internal diynes and dithiols was established, and exclusively Markovnikov poly(formyl sulfide)s (PFSs) with high molecular weights and moderate stereoregularity were produced in high yields. Because of the aromatic units and sulfur atoms in their main chains, these polymers possessed high refractive index values. By introducing the fluorene and aldehyde moieties, the resulting PFSs could act as a fluorescent sensor for sensitive hydrazine detection. Taking advantage of the reaction of the aldehyde group and hydrazine, imino-PFSs with remarkable and reversible fluorescence change through alternating fumigation with HCl and NH3 were easily acquired and further applied in multicolor patterning, a rewritable material and quadruple-mode information encryption. Additionally, a test strip of protonated imino-polymer for the tracking of bioamines in situ generated from marine product spoilage was also demonstrated. Collectively, this work not only provides a powerful click polymerization to enrich the multiplicity of sulfur-containing materials, but also opens up enormous opportunities for these functional polysulfides in diverse applications.

Vanillin-derived α,ω-diene monomer for thermosets preparation via thiol–ene click polymerization

Novel vanillin-derived α,ω-diene monomer was synthesized via Williamson and Tishchenko reaction, which was readily polymerized with thiols to obtain thiol-ene networks with tunable material properties and satisfactroy degradability under mild alkaline conditions.

Hydroxyl–yne click polymerization: a facile strategy toward poly(vinyl amino ether ester)s with color-tunable luminescence

This study established an environmentally friendly hydroxyl–yne click polymerization, which provides a new strategy for the preparation of color-tunable unconventional luminescent materials.

Photo and acid dual degradable polymeric nanoparticles from an o-nitrobenzyl dithiol with thiol–ene click polymerization

Photo and acid dual degradable polymeric nanoparticles.

Synthesis of photoactive nanocomposite hydrogels via in-situ photoinitiated thiol-ene click polymerization of acrylates containing norbornene-POSS and norbornene-POSS/Ag NPs

Radical-mediated thiol-ene photopolymerization is a method that has been studied intensively since the beginning of the century due to the nature of click chemistry which can be carried out in a fast, controllable, and easy way under mild environment conditions with no or minimal formation of by-products. In order to improve the properties of the polymeric nanocomposite materials which have been obtained by photopolymerization method and to prepare them for a particular purpose, various nano-sized photo-reactive groups or cross-linking agents have been added to the formulations. The advantage of this study for the preparation of thin-film and hydrogel nanocomposites is based on one-pot thiol-ene photo-click polymerization. The main contribution made by one-component Type II photoinitiator, 2-Mercaptothioxanthone (TX-SH) carries both thiol functionality and chromophoric group on it. Polyhedral oligomeric silsesquioxane (POSS) functionalized with 1 or 3 norbornene units was used as alkene and played a good role in the preparation of nanocomposite hydrogels with/without in-situ formed silver nanoparticles (Ag NPs) with various acrylate content by thiol-ene photo-click polymerization. Especially the good contribution of norbornenylethyl disilanol isobutyl polyhedral oligomeric silsesquioxane (1NBPOSS) or tris-norbornenyl isobutyl polyhedral oligomeric silsesquioxane (3NBPOSS) was seen in terms of conversion percentage of acrylates which was determined by photo differential scanning calorimetry (photo-DSC) and swelling ratios of hydrogels in phosphate buffer solution (PBS) buffer solution. Besides them, obtained nanocomposites displayed good thermal stability values according to the Thermogravimetric analysis (TGA) measurements and scanning electron microscopy (SEM) images confirmed rather small-sized and uniform in-situ formed Ag NPs.

Hydrophobic porous polymer containing isoxazoline and siloxane groups for 2,4,6-trinitrotoluene (TNT) adsorption via synergistic effect of Lewis acid-base, dipole-π, and π-π interactions

A series of hydrophobic porous polymer containing isoxazoline and siloxane groups were successfully prepared via catalyst-free click polymerization and freeze-drying technology. In addition to hydrophobicity, synergistic effect of three molecular aborption interactions, namely point-to-point Lewis acid-base, point-to-face dipole-π, and face-to-face π-π interactions, endowed the resulting porous polymer with good 2,4,6-trinitrotoluene (TNT) adsorption efficiency from wastewater. At the same time, the adsorption efficiency of the resulting porous polymer in different natural/polluted water samples was similar to those in laboratory, and about 80% of the initial adsorption capacity remained after five adsorption-desorption cycles. The results showed that hydrophobic porous polymer containing isoxazoline and siloxane groups is a promising adsorbent for the treatment of TNT wastewater.