Ene Chemistry Research Articles

CO2–Philic Fluorinated Porous Organic Polyaminal in Photocatalytic Thiol–Ene Chemistry: Decoding the Effect of F-Atoms

CO₂–Philic Fluorinated Porous Organic Polyaminal in Photocatalytic Thiol–Ene Chemistry: Decoding the Effect of F-Atoms

Impact of Polyester Dendrimers as Branched Multifunctional Cross-Linking Additives in Triazine-Trione-Based Composites Developed via High-Energy Visible Light Thiol–ene Chemistry

Impact of Polyester Dendrimers as Branched Multifunctional Cross-Linking Additives in Triazine-Trione-Based Composites Developed via High-Energy Visible Light Thiol–ene Chemistry

A Versatile Platform to Generate Shell-Cross-Linked Uniform Π-Conjugated Nanofibers with Controllable Length, High Morphological Stability, and Facile Surface Tailorability.

Living crystallization-driven self-assembly (CDSA) has emerged as an efficient route to generate π-conjugated-polymer-based nanofibers (CPNFs) with promising applications from photocatalysis to biomedicine. However, the lack of efficient tools to endow CPNFs with morphological stability and surface tailorability becomes a frustrating hindrance for expanding application spectrum of CPNFs. Herein, a facile strategy to fabricate length-controllable OPV-based (OPV = oligo(p-phenylenevinylene)) CPNFs containing a cross-linked shell with high morphological stability and facile surface tailorability through the combination of living CDSA and thiol-ene chemistry by using OPV5 -b-PNAAM32 (PNAAM = poly(N-allyl acrylamide)) as a model is reported. Uniform fiber-like micelles with tunable length can be generated by self-seeding of living CDSA. By taking advantage of radical thiol-ene reaction between vinyls of PNAAM corona and four-arm thiols, the shell of micelles can be cross-linked with negligible destruction of structure of vinylene-containing OPV core. The resulting micelles show high morphological stability in NaCl solution and PBS buffer, even upon heating at 80°C. The introduced extra thiol groups in the cross-linked shell can be further employed to install extra functional moieties via convenient thiol-Michael-type reaction. Given the negligible cytotoxicity of resulting CPNFs, this strategy opens an avenue to fabricate various CPNFs of diverse functionalities for biomedicine.

Reactive Compatibilization of Impact Copolymer Polypropylene and Organically Modified Mesoporous Silica to Prepare Composites Possessing Enhanced Mechanical Properties

Mesoporous silica was evaluated as functionalized filler in impact copolymer polypropylene (ICP) in its original form as well as after organic modification. Mesoporous silica was synthesized by base-catalyzed hydrolysis of tetraethyl orthosilicate in the water–acetone medium. The organic modification of mesoporous silica was carried out using commercially available silane with a terminal unsaturated bond and by synthesizing silane precursor by chemical treatment via TEMPO-initiated thiol–ene chemistry to introduce alkyl chains terminating in hydroxyl groups. The characterization for all types of mesoporous silica prepared was done using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), solid-state nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) analysis, X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). ICP–mesoporous silica composites were prepared using 1, 5, and 10 phr mesoporous silica and organically modified mesoporous silica loading via reactive compatibilization and were tested for their thermal, morphological, rheological, and mechanical properties. The addition of mesoporous and organically modified mesoporous silica enhanced thermal stability and nucleation with respect to neat ICP. Tensile and flexural moduli were improved while maintaining their impact strength. Analysis of rheological properties revealed a rise in zero-shear rate viscosity in ICP–mesoporous silica composites. DMA studies showed higher storage and loss modulus with the addition of mesoporous silica in ICP.

Photo‐Patternable Stretchable Semi‐Interpenetrating Polymer Semiconductor Network Using Thiol–Ene Chemistry for Field‐Effect Transistors

AbstractStretchable polymer semiconductors are an essential component for skin‐inspired electronics. However, the lack of scalable patterning capability of stretchable polymer semiconductors limits the development of stretchable electronics. To address this issue, photo‐curable stretchable polymer blends consisting of a high‐mobility donor–acceptor conjugated polymer and an elastic rubber through thiol–ene chemistry are developed. The thiol–ene reaction can selectively cross‐link the rubber with alkene or vinyl groups without damaging the electronic properties of the conjugated polymer. The conjugated polymer chains embedded in the elastic polymer matrix induce a semi‐interpenetrating polymer network (SIPN). The thiol–ene‐cross‐linked network provides great solvent resistance and enhances stretchability for the embedded conjugated polymer. The well‐defined patterned film with a feature size of ≈10 µm can be obtained using UV light at 365 nm through conventional photolithography processes. Furthermore, the SIPN‐based transistors show increased mobilities from 0.61 to 1.18 cm2 V−1 s−1 when applying the strain from 0% to 100%. Moreover, the hole mobility can still maintain at 0.87 cm2 V−1 s−1 after 1000 strain‐and‐release cycles at the strain of 25%. This study sheds light on the molecular design of photo‐curable polymer semiconductors for the mass production of stretchable circuits.

Poly(N-allyl acrylamide) as a Reactive Platform toward Functional Hydrogels.

The synthesis of poly(N-allyl acrylamide) (PNAllAm) as a platform for the preparation of functional hydrogels is described. The PNAllAm was synthesized via organocatalyzed amidation of poly(methyl acrylate) (PMA) with allylamine and characterized by 1H NMR spectroscopy, size exclusion chromatography (SEC), and turbidimetry, which allowed an estimation of the lower critical solution temperature of ∼26 °C in water. The PNAllAm was then used to make functional hydrogels via photoinitiated thiol-ene chemistry, where dithiothreitol (DTT) was used to cross-link the polymer chains. In addition, mercaptoethanol (ME) was added as a functional thiol to modulate the hydrogel properties. A decrease of the volume-phase transition temperature of the resulting hydrogels was observed with increasing ME content. Altogether this work introduces a straightforward way for the preparation of PNAllAm from PMA and demonstrates its value as a reactive polymer platform for the generation of functional hydrogels.

Rapid synthesis of functional poly(ester amide)s through thiol-ene chemistry.

Poly(ester amide)s (PEAs) bearing various side chains were synthesized by post-polymerization modification of PA-1, a vinylidene containing PEA. The thiols 1-dodecanethiol (1A-SH), 2-phenylethanethiol (1B-SH), 2-mercaptoethanol (1C-SH), thioglycolic acid (1D-SH), furfuryl mercaptan (1E-SH) and sodium-2-mercaptoethanesulfonate (1F-SH) were reacted with PA-1 to form PEAs PA-1A through PA-1F respectively. PEAs containing non-polar thiol side chains (PA-1A, PA-1B, PA-1E), showed little change in solubility compared to PA-1, while PEAs with more polar side chains improved solubility in more polar solvents. PA-1F, functionalized with sodium-2-mercaptoethanesulfonate, became water-soluble. The introduction of pendant functional groups impacted the thermal behaviors of PEAs in a wide range. The PEAs were thermally stable up to 368 °C, with glass transition temperatures (Tg) measured between 117 to 152 °C. Moreover, to demonstrate the versatility of the PEAs, thermal reprocessable networks and polyurethanes were successfully fabricated by reacting with a bismaleimide (1,6-bis(maleimido)hexane, 1,6-BMH) and a diisocyanate (4,4'-diphenylmethane diisocyanate, 4,4'-MDI), respectively. This study paves the way for the facile synthesis of functional poly(ester amide)s with great potential in many fields.

Matrix metalloproteinase responsive hydrogel microplates for programmed killing of invasive tumour cells.

Interactive materials are an emerging class of systems that can offer control over response and adaptivity in polymer structures towards the meso- and macroscale. Here, we use enzyme regulated cleavage of peptide crosslinkers in polymer hydrogels to release a cytotoxic therapeutic nanoparticle with an adaptable mechanism. Hydrogel microplates were formed through polyethylene glycol/peptide photoinitiated thiol-ene chemistry in a soft-lithography process to give square plates of 20 by 20 μm with a height of 10 μm. The peptide was chosen to be degradable in the presence of matrix metalloproteinase 2/9 (MMP-2/9). The hydrogel material's mechanical properties, swelling, and protease degradation were characterised. The microfabricated hydrogels were loaded with docetaxel (DTXL) containing poly(dl-lactide-co-glycolide) (PLGA) nanoparticles, and characterised for enzyme responsivity, and toxicity to MMP-2/9 overexpressing brain cancer cell line U87-MG. A 5-fold decrease in EC50 was seen compared to free DTXL, and a 20-fold decrease was seen for the MMP responsive microplates versus a non-degradable control microplate. Potential applications of this system in post-resection glioblastoma treatment are envisioned.

Vat 3D printing of full-alginate hydrogels via thiol–ene reactions towards tissue engineering applications

Different synthetic strategies are explored to functionalize alginate with thiol and alkene groups. In this way an innovative full-alginate ink for digital light processing printers, based on the more biocompatible thiol–ene chemistry, is proposed.

Zwitterionic Polypeptoids: A Promising Class of Antifouling Bioinspired Materials.

Biofouling caused by protein adsorption and microbial colonization remains a great challenge in many applications. In this work, we synthesized a new type of zwitterionic polypeptoid containing carboxybetaine (CB) moieties (PeptoidCB) through thiol–ene chemistry of poly(N-allylglycine) (PNAG). The zwitterionic antifouling hydrogel was subsequently prepared by co-mixing PeptoidCB with agarose, which exhibited excellent resistance to non-specific protein adsorption and bacterial adhesion. Further, PeptoidCB-modified block copolypeptoids with amphiphilic structure were synthesized to form nanoparticles in an aqueous solution with neglected protein adsorption. The ability of PeptoidCB to resist non-specific protein adsorption and bacterial adhesion makes it a promising candidate for biomedical and industrial applications.

Manipulating the Relative Rates of Reaction and Diffusion in a Holographic Photopolymer Based on Thiol–Ene Chemistry

Properly balanced reaction and diffusion kinetics are crucial for achieving optimal performance in holographic photopolymers. However, a comprehensive study on the effect of reaction and diffusion on the performance of thiol–ene-based holographic photopolymers has not been performed previously. To determine the relationship between reaction and diffusion, the refractive index modulation (Δn) of holographic gratings recorded in a model thiol–ene photopolymer system was evaluated with controlling the rates of reaction and diffusion processes. By changing the molecular weight of the polymer binder, the diffusion rate was varied over orders of magnitudes with the highest Δn of 0.026 achieved at a molecular weight of 2.9 × 104 Da. Meanwhile, the haze was significantly reduced in binders of higher molecular weight. Similarly, as the reaction rate was reduced in accordance with lowering the light intensity, the Δn reached a peak value of 0.023 at 7 mW/cm2 and was found to decrease at both higher (2500 lines/mm) and lower (1000 lines/mm) spatial frequencies. In particular, Δn approaching 0 was observed at a very low intensity (2 mW/cm2) and when the binder with a molecular weight as low as 0.5 × 104 Da was used. An analogous formulation incorporating a secondary thiol, which has slower reaction kinetics and a more stable thiyl radical relative to the primary thiol, exhibited a lower Δn , especially at higher spatial frequencies. Through one-step thiol-Michael addition, the functionality of a tetrathiol monomer was reduced to various extents to obtain a series of thiol–ene photopolymers with precise control over gel point conversions, among which the thiol with an average functionality of 3.5 realized the highest Δn of 0.028. An enhanced reactive binder with norbornene pendant groups was also synthesized, and holographic gratings recorded in it showed notably higher Δn at low light intensities compared to those recorded in non-reactive or less reactive binders.

Ambient temperature cross-linking of a sustainable, cardanol-based cyanate esterviasynergistic thiol–ene copolymerization

A cyanate ester derived from bio-based cardanol was cross-linked at room temperatureviasynergistic thiol–ene chemistry catalyzed by UV irradiation.

Glycopolymer Microarrays with Sub‐Femtomolar Avidity for Glycan Binding Proteins Prepared by Grafted‐To/Grafted‐From Photopolymerizations

AbstractWe report a novel glycan array architecture that binds the mannose‐specific glycan binding protein, concanavalin A (ConA), with sub‐femtomolar avidity. A new radical photopolymerization developed specifically for this application combines the grafted‐from thiol–(meth)acrylate polymerization with thiol–ene chemistry to graft glycans to the growing polymer brushes. The propagation of the brushes was studied by carrying out this grafted‐to/grafted‐from radical photopolymerization (GTGFRP) at >400 different conditions using hypersurface photolithography, a printing strategy that substantially accelerates reaction discovery and optimization on surfaces. The effect of brush height and the grafting density of mannosides on the binding of ConA to the brushes was studied systematically, and we found that multivalent and cooperative binding account for the unprecedented sensitivity of the GTGFRP brushes. This study further demonstrates the ease with which new chemistry can be tailored for an application as a result of the advantages of hypersurface photolithography.

Attenuating Fibrotic Markers of Patient-Derived Dermal Fibroblasts by Thiolated Lignin Composites.

We report the use of phenolic functional groups of lignosulfonate to impart antioxidant properties and the cell binding domains of gelatin to enhance cell adhesion for poly(ethylene glycol) (PEG)-based scaffolds. Chemoselective thiol–ene chemistry was utilized to form composites with thiolated lignosulfonate (TLS) and methacrylated fish gelatin (fGelMA). Antioxidant properties of TLS were not altered after thiolation and the levels of antioxidation were comparable to those of L-ascorbic acid. PEG-fGelMA-TLS composites significantly reduced the difference in COL1A1, ACTA2, TGFB1, and HIF1A genes between high-scarring and low-scarring hdFBs, providing the potential utility of TLS to attenuate fibrotic responses.

A facile strategy for the development of n‒type carbon nanotube composites with tunable thermoelectric properties via thiol‒ene chemistry

This work exploits thiol‒ene chemistry for the development of carbon nanotubes (CNTs) ‒based, solution‒processed, and flexible thermoelectric (TE) composites. A systematic study was implemented by optimizing many aspects: (i) use of π‒conjugated vs non‒conjugated linkers, (ii) amount and type of CNTs (SWNT vs MWNT) in the composite, and (iii) doping. The resulting samples revealed that the materials exhibited n‒type semiconducting behavior without requiring a doping process and attained power factors (PF) up to 1.1 μW m−1 K−2. It was also found that the composites made with non‒conjugated linkers showed better TE performance than that of π‒conjugated linkers. Besides n‒type materials, this methodology is also capable of producing p‒type materials, and n‒type materials can also convert to p‒type upon doping exposure. A variety of distinct surface morphologies with segregated structures were observed on scanning electron microscopy (SEM). The methodology which has been benefited here relies on the factors beyond just the blend composition or type of CNTs used, including the specific structure of the linkers, doping process, and the morphology resulting from the cross‒linking composites.

Silicone Polymers—Celebrating 80 Years of the Direct Process

Silicone Polymers—Celebrating 80 Years of the Direct Process

Design and synthesis of highly fluorescent and stable fullerene nanoparticles as probes for folic acid detection and targeted cancer cell imaging

Rational design and construction of fullerene derivatives play significant roles in the development of applications for sensing, marking and imaging in biomedical fields. In the present work, a novel type of C60 fluorescent nanoparticle (C60 FNP) was synthesized by a combination of thiol–ene chemistry and modification with folic acid (FA). The as-prepared C60 FNPs exhibited intense blue luminescence with a relatively high quantum yield of 26%, which is higher than that of any other reported fluorescent fullerene-based nanomaterial. Moreover, they revealed superior photobleaching resistance under constant UV lamp illumination for 5 h and excellent photostablity after 9 months of storage in water. Due to the mutual hydrogen bond interaction, the obtained C60 FNPs were capable of acting as a sensitive and specific probe for FA detection and quantification, with a liner range of 0 to 80 μM and a detection limit of 0.24 μM. Satisfactory recoveries (95.4%–105.2%) were obtained from a series of actual samples, further confirming the feasibility of this nanoprobe. Additionally, taking advantage of the FA moiety, the C60 FNPs had easy access to penetrate into cancer cells with higher expression levels of folate receptors, thereby achieving the function of targeted cellular imaging.

Fabricating poly(vinyl alcohol)/gelatin composite sponges with high absorbency and water-triggered expansion for noncompressible hemorrhage and wound healing.

It is challenging for traditional hemostatic sponges to control massive and noncompressible hemorrhages in the military field and accidental trauma. In this work, a series of highly fluid-absorbent composite sponges with rapid expansion ability based on norbornene anhydride-modified poly(vinyl alcohol) and gelatin (PVA@Gel-Sps) were developed by a foaming technique, chemical and physical crosslinking reactions and lyophilization. The prepared PVA@Gel-Sp2 exhibited a 3500% maximum water absorption ratio with a fast water absorption speed, which was suitable for blood component concentration. Owing to its interconnected macroporous structure, robust mechanical strength and high resilience, the compressed sponge could rapidly re-expand to more than 10 times its volume in response to water and blood. Moreover, due to the synergistic effect of the PVA-based sponge and gelatin, PVA@Gel-Sp2 could obviously shorten the hemostasis time and reduce blood loss in SD rat liver defect noncompressible hemorrhage models, and exhibited better wound healing effects in a full-thickness skin defect model than commercial sponges. These results suggest that PVA@Gel-Sp2 is a potential candidate for controlling noncompressible hemorrhage and promoting wound healing.

Getting control of hydrogel networks with cross-linkable monomers.

The structure of a hydrogel network determines its ability to dissipate stress upon deformation, as well as its ability to swell in water. By designing systems with cross-linkable thiol groups in the monomers, radical thiol-ene chemistry was used to form controlled networks for acrylamide monomers. The use of radical thiol-ene chemistry effectively suppressed homo-polymerization of the bis(acrylamide) monomer and resulted in networks of alternating thiol and acrylamide monomers. Additionally, if the stoichiometry between the monomers is controlled, the network should approach that of ideality. In the case of bis(acrylamide) monomers, the incorporation of hydrogen-bond donors into the network creates a single network hydrogel with the benefits of high strength and ductility from the simultaneous incorporation of chemical and physical cross-links. Additionally, this strategy suppresses the formation of homo-polymerization in the acrylamide monomer to achieve an alternating network, which is supported with NMR characterization of base-digested fragments. For three different monomer compositions, the resulting gels had high compressive strength (up to 40 MPa) and tunable mechanical properties. The high mechanical strength of the 1 : 1, thiol : ene gel composition is due to the uniform distribution of cross-links, which creates defect-free networks for efficient stress transfer. The present one-pot synthetic strategy toward controlled gel networks affords monomer versatility and synthetic ease, as well as the potential for mechanically robust materials.

In Situ Polymer Analogue Generation of Azlactone Functions at Poly(oxazoline)s for Peptide Conjugation

AbstractThe physical and chemical stability of peptides for biomedical applications can be greatly enhanced through the conjugation of polymers. A well‐known but rather underemployed selective coupling functionality is the azlactone group, which readily reacts with a number of different nucleophiles without the need for activation and the formation of any by‐products. For example, azlactone functional polymers are used to react with peptides and proteins, rich in amino and thiol groups, to form polymeric beads for affinity‐based column chromatography. So far, side chain functional azlactone polymers have been mainly synthesized by radical polymerization using 2‐vinyl‐4,4‐dimethyl azlactone together with different acrylate monomers. Here, a new azlactone precursor equipped with a functional thiol is presented, which can be attached to any vinyl functional polymer by thiol–ene chemistry. Subsequently, the formation of the reactive azlactone ring can be performed in situ at high conversion rate without the need for illumination. This approach is tested on an azlactone side functional poly(2‐oxazoline) by coupling amine containing molecules including a model peptide and is proven via 1H NMR spectroscopy, IR spectroscopy, as well as HPLC measurements.