Thiol-ene Polymerization Research Articles

Development of Functional Biointerface Using Mixed Zwitterionic Silatranes.

Strategies to design multifunctional interfaces for biosensors have been extensively investigated to acquire optimal sensitivity, specificity, and accuracy. However, heterogeneous ingredients in clinical samples inevitably generate background signals, exposing challenges in biosensor performance. Polymer coating has been recognized as a crucial method to functionalize biointerfaces by providing tailored properties that are essential for interacting with biological systems. Herein, we introduce for the first time two oligomeric silatranes, MPS-MPCn and MPS-PEGMACOOHm, which were copolymerized from mercaptopropylsilatrane (MPS) with either zwitterionic monomer 2-methacryloyloxyethyl phosphorylcholine (MPC) or carboxylated poly(ethylene glycol) methacrylate (PEGMACOOH) through thiol-ene polymerization. These oligomeric silatranes were prepared individually and in combinations in acidic and nonacid solvents for deposition on silicon wafers. Afterward, coating properties, including wettability, thickness, and elemental composition, were characterized by contact angle meter, ellipsometer, and X-ray photoelectron spectroscopy (XPS), respectively. Importantly, MPS-MPCn polymers were found to form thin films with high hydrophilicity and superior fouling repulsion to bacteria and protein, while mixed coating involving 70% MPS-PEGMACOOH2.5 and 30% MPS-MPC2.5 exhibited thinnest coating with best wettability among COOH-terminated coatings. Furthermore, the functional COOH group in the coated surfaces was exploited for postmodification with biological molecules via intermediated N-hydroxysuccinimide (NHS) ester group by amine coupling chemistry. Once again, the combination of 70% MPS-PEGMACOOH2.5 and 30% MPS-MPC2.5 provided an ultimate reduction in nonspecific adsorption (NSA) and established a finest signal discrimination through enzyme-linked immunosorbent assay. Consequently, these novel mixed oligomeric silatranes offer a promising approach for the construction of biosensor interfaces with dual functions in both nonspecific binding prevention and conjugation of biomolecules.

Photocurable Thiol-Ene/Nanocellulose Elastomeric Composites for Bioinspired and Fluorine-Free Superhydrophobic Surfaces.

Artificially prepared superhydrophobic surfaces toward a self-cleaning "lotus effect" and anticontamination performance have become critically important in the past few years. However, most approaches to create the required topology with a hierarchical roughness comprise several manufacturing steps of varying practicality. Moreover, the desired low surface energy is in most cases achieved with fluorinated moieties that are currently criticized due to biological and environmental hazards. In this work, rapidly photocuring but weak thiol-ene resins were reinforced with cellulose nanofibrils (CNFs) to replicate lotus leaves via one-step UV nanoimprint lithography. The CNFs were surface-modified using countercation exchange of carboxyl groups and grafting of thiol and methacrylate functionalities. The formulation methodology resulted in free-flowing, shear-thinning composite resins without surfactants or dispersants. The rheological and photo-cross-linking behavior of the resins, the thermal stability, the mechanical performance, and the hydrophobicity of the cured composites were characterized. Notably, the surface modifications increased the as received fibril diameter (1.9 ± 0.6 nm) by 1.6-2.3 nm and raised the fibril-resin compatibility. The resins underwent rapid polymerization and the high thermal stability of thiol-enes was retained. The methacrylated nanofibrils (10 vol %) significantly strengthened the rubbery network, outperforming the neat thiol-ene polymer in terms of hardness (3.4×), reduced modulus (5.8×), and wear resistance (>100×). Moreover, the surface of lotus-texturized composites was superhydrophobic with a water contact angle of 155°, higher than that of the neat polymer (147°), and was self-cleaning. These CNF composite resins are compatible with fast-cure processes such as 3D printing and roll-to-roll processing, are exempt of fluorine or any other hydrophobization treatment, and are extremely wear-resistant.

Construction and Regulation on Thiol–Acrylate Networks through Binary Polymerization of Thiol–Ene Polymerization and Free Radical Polymerization

Construction and Regulation on Thiol–Acrylate Networks through Binary Polymerization of Thiol–Ene Polymerization and Free Radical Polymerization

(Invited) Silicon Nanocrystals and Electrum Nanoclusters with High Quantum Yield for Light Converting Applications

While QDs are typically made of semiconductors, metals at low dimensions also turn to discrete electronic structure. The characteristic transition size from bulk to nanodot is lower, because Fermi level position is at the band middle, while discretization of levels starts from the band edge. Therefore, only for sizes of a metal entity ~ 1 nm a QD-like behavior manifests.Here we show that metal nanoclusters Au16Ag7 of an electrum alloy (gold-silver) with adamantanethiolate ligands possess PL quantum yield of ~ 70% in a thiol-ene polymer matrix [1]. PL is in NIR range with a large Stokes shift. Due to parity-forbidden transition the PL lifetime is in microseconds. These characteristics are similar to silicon QDs, where optical transition is also partly forbidden. Luminescence from Si QDs (5-10 nm size) may also feature high quantum efficiency when a defect-free core with good surface passivation is prepared. We have demonstrated a new synthesis method, which can reduce precursor cost by an order of magnitude from the established HSQ-based technique [2]. Si QDs prepared in this way have near-unity internal and > 50% external (quantum yield) efficiency with a large Stokes shift. In both nanomaterials the re-absorption is suppressed, which is of value for several applications.One such application is a semi-transparent photovoltaics for glazing in building-integration. It is based on a luminescent solar concentrator concept, where high efficiency and a large Stokes shift are necessary requirements for nanophosphors. In this configuration absorbed solar light is re-emitted and a large fraction of it is guided by total internal reflection to the edges for collection by standard solar cells. As a proof-of-concept we fabricated 20x20 cm2 prototypes, where Si QD-doped polymer layer is sandwiched between glass plates in a triplex geometry. Such “solar windows” feature high transparency (>80%), low haze (<3%), high color rendering index (~ 88) and, at the same time, deliver up to 0.6 W of electrical peak power under one sun [3]. Original measurement techniques were developed to characterize large-area devices [4,5].

Improving the removal rate of bisphenol A and Cu2+ from water using P/N coexisting β-cyclodextrin-based adsorbents by enhancing adsorbents-pollutants interactions

Bisphenol A (BPA), a prominent endocrine-disrupting compound, has garnered considerable attention due to its urgent need for rapid removal from water. Herein, we first used a novel reactive phosphine oxide containing tertiary amines as crosslinker to prepare water-insoluble crosslinked β-cyclodextrin (β-CD) adsorbent via radical-mediated thiol–ene polymerization. Owing to the synergistic hydrogen-bond (H-bond) interactions of functional groups (tertiary amine and PO groups) toward BPA, the resulted adsorbents showed fast adsorption kinetics to BPA with an adsorption equilibrium time of 5 min. After six adsorption–desorption cycles, the removal efficiency of BPA was 92.5 %, indicating its excellent reusability. Due to the presence of the CS bonds, the β-CD -derived bio-adsorbents offered binding sites for Cu2+ ions, resulting in a maximum adsorption capacity of 113.89 mg g−1.

Quercetin allylation and thiol–ene click photopolymerization to produce biobased polymer thermosets with robust thermomechanical properties

AbstractThe development of biobased and functionalized monomers along with eco‐friendly photopolymerization processes represent promising methods for the development of renewable and more environmentally friendly thermosets. Thiol–ene ‘click’ photopolymerization is particularly advantageous in this regard; however, the materials derived from this method often exhibit low glass transition temperatures (Tg) and unsuitable thermomechanical properties for applications at room temperature. Herein, we report the synthesis of biobased allyl derivatives from quercetin, a renewable flavonoid compound widely available in fruits, vegetables and plants. We demonstrated the isolation of tetra‐ and penta‐allylated quercetin (Q1 and Q2, respectively) and their subsequent photoactivated thiol–ene polymerization. By introducing a biobased thiol curing agent (PTTMP) derived from glycerol and mercaptopropionic acid, we produced fully biobased crosslinked thermosets with high content of aromatic moieties provided by the framework of the monomers. Real‐time infrared spectroscopy showed the effective thiol–ene photopolymerization of Q1 and Q2 and PTTMP with conversions of 60% and 75%, respectively, after 15 min of UV irradiation. Due to the modulated crosslinking degree from the allyl group functionalization in the monomers, the biobased crosslinked networks showed storage moduli from 420 to 739 MPa, thermal stability from 220 to 257 °C and Tg values ranging from 75 to 90 °C. This work outlines straightforward strategies for creating biobased thermosets that overcome the limited thermomechanical properties of thiol–ene networks and offer potential antimicrobial and antioxidant properties. © 2024 Society of Chemical Industry.

Xylose- and Nucleoside-Based Polymers via Thiol-ene Polymerization toward Sugar-Derived Solid Polymer Electrolytes.

A series of copolymers have been prepared via thiol-ene polymerization of bioderived α,ω-unsaturated diene monomers with dithiols toward application as solid polymer electrolytes (SPEs) for Li+-ion conduction. Amorphous polyesters and polyethers with low Tg's (-31 to -11 °C) were first prepared from xylose-based monomers (with varying lengths of fatty acid moiety) and 2,2'-(ethylenedioxy)diethanethiol (EDT). Cross-linking by incorporation of a trifunctional monomer also produced a series of SPEs with ionic conductivities up to 2.2 × 10-5 S cm-1 at 60 °C and electrochemical stability up to 5.08 V, a significant improvement over previous xylose-derived materials. Furthermore, a series of copolymers bearing nucleoside moieties were prepared to exploit the complementary base-pairing interaction of nucleobases. Flexible, transparent, and reprocessable SPE films were thus prepared with improved ionic conductivity (up to 1.5 × 10-4 S cm-1 at 60 °C), hydrolytic degradability, and potential self-healing capabilities.

Impact of Interfaces on the CO2 Permeability of Photopatterned Two-Stage Thiolene Polymer Films

Impact of Interfaces on the CO₂ Permeability of Photopatterned Two-Stage Thiolene Polymer Films

Enlarging the Stokes shift of CuInS2 quantum dots using thiol–ene polymers for efficient large-area luminescent solar concentrators

A thiol–ene polymer is employed to enlarge the Stokes shift of CuInS2/ZnS quantum dots for application in luminescent solar concentrators (LSCs), and a certified record power conversion efficiency of 1.36% (area of 29 × 29 cm2) was achieved.

Extending the shelf life of HLM chips through freeze-drying of human liver microsomes immobilized onto thiol-ene micropillar arrays.

Microfluidic flow reactors functionalized with immobilized human liver microsomes (HLM chips) represent a powerful tool for drug discovery and development by enabling mechanism-based enzyme inhibition studies under flow-through conditions. Additionally, HLM chips may be exploited in streamlined production of human drug metabolites for subsequent microfluidic in vitro organ models or as metabolite standards for drug safety assessment. However, the limited shelf life of the biofunctionalized microreactors generally poses a major barrier to their commercial adaptation in terms of both storage and shipping. The shelf life of the HLM chips in the wetted state is ca. 2-3 weeks only and requires cold storage at 4 °C. In this study, we developed a freeze-drying method for lyophilization of HLMs that are readily immobilized inside microfluidic pillar arrays made from off-stoichiometric thiol-ene polymer. The success of lyophilization was evaluated by monitoring the cytochrome P450 and UDP-glucuronosyltransferase enzyme activities of rehydrated HLMs for several months post-freeze-drying. By adapting the freeze-drying protocol, the HLM chips could be stored at room temperature (protected from light and moisture) for at least 9 months (n = 2 independent batches) and up to 16 months at best, with recovered enzyme activities within 60-120% of the non-freeze-dried control chips. This is a major improvement over the cold-storage requirement and the limited shelf life of the non-freeze-dried HLM chips, which can significantly ease the design of experiments, decrease energy consumption during storage, and reduce the shipping costs with a view to commercial adaptation.

Biobased Transparent Thiol–Ene Polymer Networks from Levoglucosan

Biobased Transparent Thiol–Ene Polymer Networks from Levoglucosan

Non-isocyanate polyurethanes synthesized from terpenes using thiourea organocatalysis and thiol-ene-chemistry

The depletion of fossil resources as well as environmental concerns contribute to an increasing focus on finding more sustainable approaches for the synthesis of polymeric materials. In this work, a synthesis route towards non-isocyanate polyurethanes (NIPUs) using renewable starting materials is presented. Based on the terpenes limonene and carvone as renewable resources, five-membered cyclic carbonates are synthesized and ring-opened with allylamine, using thiourea compounds as benign and efficient organocatalysts. Thus, five renewable AA monomers are obtained, bearing one or two urethane units. Taking advantage of the terminal double bonds of these AA monomers, step-growth thiol-ene polymerization is performed using different dithiols, to yield NIPUs with molecular weights of above 10 kDa under mild conditions. Variation of the dithiol and amine leads to polymers with different properties, with Mn of up to 31 kDa and Tg’s ranging from 1 to 29 °C.

Multifaceted Shape Memory Polymer Technology for Biomedical Application: Combining Self-Softening and Stretchability Properties.

Thiol-ene polymers are a promising class of biomaterials with a wide range of potential applications, including organs-on-a-chip, microfluidics, drug delivery, and wound healing. These polymers offer flexibility, softening, and shape memory properties. However, they often lack the inherent stretchability required for wearable or implantable devices. This study investigated the incorporation of di-acrylate chain extenders to improve the stretchability and conformability of those flexible thiol-ene polymers. Thiol-ene/acrylate polymers were synthesized using 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO), Trimethylolpropanetris (3-mercaptopropionate) (TMTMP), and Polyethylene Glycol Diacrylate (PEGDA) with different molecular weights (Mn 250 and Mn 575). Fourier Transform Infrared (FTIR) spectroscopy confirmed the complete reaction among the monomers. Uniaxial tensile testing demonstrated the softening and stretching capability of the polymers. The Young's Modulus dropped from 1.12 GPa to 260 MPa upon adding 5 wt% PEGDA 575, indicating that the polymer softened. The Young's Modulus was further reduced to 15 MPa under physiologic conditions. The fracture strain, a measure of stretchability, increased from 55% to 92% with the addition of 5 wt% PEGDA 575. A thermomechanical analysis further confirmed that PEGDA could be used to tune the polymer's glass transition temperature (Tg). Moreover, our polymer exhibited shape memory properties. Our results suggested that thiol-ene/acrylate polymers are a promising new class of materials for biomedical applications requiring flexibility, stretchability, and shape memory properties.

Synthesis and Crystallization of Waterborne Thiol-ene Polymers: Toward Innovative Oxygen Barrier Coatings.

The synthesis of waterborne thiol-ene polymer dispersions is challenging due to the high reactivity of thiol monomers and the premature thiol-ene polymerization that leads to high irreproducibility. By turning this challenge into an advantage, a synthesis approach of high solid content film-forming waterborne poly(thioether) prepolymers is reported based on initiator-free step growth sonopolymerization. Copolymerization of bifunctional thiol and ene monomers diallyl terephthalate, glycol dimercaptoacetate, glycol dimercaptopropionate, and 2,2-(ethylenedioxy)diethanethiol gave rise to linear poly(thioether) functional chains with molar mass ranging between 7 and 23 kDa when synthesized at 30% solid content and between 1 and 9 kDa at increased solid content of 50%. To further increase the polymers' molar mass, an additional photopolymerization step was performed in the presence of a water-soluble photoinitiator, i.e., lithium phenyl-2,4,6-trimethylbenzoylphosphinate, leading to high molar mass chains of up to 200 kDa, the highest reported so far for step grown poly(thioethers). The polymer dispersions presented good film-forming ability at room temperature, yielding semicrystalline films with a high potential for barrier coating applications. Nevertheless, affected by the polymer chemical repeating structure, which includes an aromatic ring, these thiol-ene chains can only crystallize very slowly from the molten state. Herein, for the first time, we present the successful implementation of a self-nucleation (SN) procedure for these types of poly(thioethers), which effectively accelerates their crystallization kinetics.

Tris-benzo[cd]indole Cyanine Enables the NIR-photosensitized Radical and Thiol-ene Polymerizations at 940 nm.

A near-infrared-absorbing heptamethine (HM+) incorporating three bulky benzo[cd]indole heterocycles was designed to efficiently prevent self-aggregation of the dye, which results in a strong enhancement of its photoinitiating reactivity as compared to a parent bis-benzo[cd]indole heptamethine (HMCl+) used as a reference system. In this context, we highlight an efficient free-radical NIR-polymerization up to a 100% acrylates C=C bonds conversion even under air conditions. Such an important initiating performance was obtained by incorporating our NIR-sensitizer into a three-component system leading to its self-regeneration. This original photoredox cycle was thoroughly investigated through the identification of each intermediary species using EPR spectroscopy.

One-pot preparation of bi-functional POSS-based hybrid monolith via photo-initiated polymerization for isolation of extracellular vesicles

Extracellular vesicles (EVs) are important participants in numerous pathophysiological processes, and could be used as valuable biomarkers to detect and monitor various diseases. However, facile EV isolation methods are the essential and preliminary issue for their downstream analysis and function investigation. In this work, a polyhedral oligomeric silsesquioxanes (POSS) based hybrid monolith combined metal affinity chromatography (MAC) and distearoyl phospholipid ethanolamine (DSPE) function was developed via photo-initiated thiol-ene polymerization. This synthesis process was facile, simple and convenient, and the obtained hybrid monolith could be applied to efficiently isolate EVs from bio-samples by taking advantages of the specific bond of Ti4+ and phosphate groups on the phospholipid membrane of EVs and the synergistic effect of DSPE insertion. Meanwhile, the eluted EVs could maintain their structural integrity and biological activity, suggesting they could be used for downstream application. Furthermore, 75 up-regulated proteins and 56 down-regulated proteins were identified by comparing the urinary EVs of colorectal cancer (CRC) patients and healthy donors, and these proteins might be used as potential biomarkers for early screening of CRC. These results demonstrated that this hybrid monolith could be used as a simple and convenient tool for isolating EVs from bio-samples and for wider applications in biomarker discovery.

Robust Vanillin-Derived Poly(thioether imidazoles) as Both a Latent Curing and Toughening Agent for One-Component Epoxy Resins.

One-component epoxy resins based on latent curing agents have garnered research attention owing to their outstanding storage stability and excellent processability, while their development considerably depends on the design and preparation of sustainable latent curing agents. Herein, taking structural advantage of lignin-derived vanillin, a biobased polymerizable aromatic imidazole monomer with α,ω-diene functionality was designed and prepared, which was applicable in subsequent thiol-ene polymerization, yielding a series of robust poly(thioether imidazoles) with excellent tunability of the structure and properties. The findings indicated that the precursors comprising poly(thioether imidazole) and commercially available epoxy resins could keep their fluidity at 25 °C for over 90 days and rapidly cured into resins under elevated temperature, demonstrating that the poly(thioether imidazole) can serve as both a latent curing and toughening agent for one-component epoxy resins because of homopolymerization initiated by imidazole groups and the introduction of an aliphatic chain in the as-prepared poly(thioether imidazole) matrix.

Sustainable macromolecular antioxidants from eugenol with synergistically enhanced storage stability for active PVA packaging

A series of linear macromolecular antioxidants (MAOs) with main-chain phenol or catechol groups were successfully prepared using eugenol as a renewable resource via thiol-ene polymerization. 1H NMR, Fourier Transform Infrared Spectrometry (FT-IR) and Gel Permeation Chromatography (GPC) were utilized to confirm their molecular structures and molecular weights. The DPPH assay was utilized to study their antioxidation capability and room temperature storage stability. Coexisting of 1,2-diol moieties was found to contribute to the long-term storage stability of the catechol type MAOs. Moreover, composite films of poly(vinyl alcohol) (PVA) with a methanol soluble MAOs were prepared through solution cast, and exhibited enhanced mechanical strength and toughness. The composite films were also endowed with antioxidation properties, potentially applicable as active packaging materials.

Polysilsesquioxane Gate Dielectric Layers Cured by UV Light Irradiation Using Thiol–Ene Reaction for Organic Thin‐Film Transistors

Polysilsesquioxane (PSQ) is used to make gate dielectric layers with pentacene to create thin‐film transistors (TFTs) by incorporating 3‐mercaptopropyl functional groups for UV light‐initiated thiol–ene polymerization with vinyl‐containing cross‐linkers. The dielectric constant (ε) of the polymerized PSQ films is controlled by the ratio of 3‐mercaptopropyl groups. When the 3‐mercaptopropyl group comprises 20%, it yields a polymerized film with a ε of 4.2 ± 0.2; upon decreasing this proportion to 10%, the ε for the subsequent film became 3.5 ± 0.2. The hole mobility of the fabricated pentacene TFTs is observed to increase as ε decreases, reaching a maximum of 0.96 cm2 V−1 s−1.

Thermally Latent Bases in Dynamic Covalent Polymer Networks and their Emerging Applications.

A novel strategy allowing temporal control of dynamic bond exchange in covalently crosslinked polymer networks via latent transesterification catalysts is introduced. Obtained by a straightforward air- and water-tolerant synthesis, the latent catalyst is designed for an irreversible temperature-mediated release of a strong organic base. Its long-term inactivity at temperatures below 50 °C provides the unique opportunity to equip dynamic covalent networks with creep resistance and high bond-exchange rates, once activated. The presented thermally latent base catalyst is conveniently introducible in readily available building blocks and, as proof of concept, applied in a radically polymerized thiol-ene network. Light-mediated curing is used for 3D-printing functional objects, on which the possibility of spatially controlled reshaping and welding based on dynamic transesterification is illustrated. Since the catalyst is thermally activated, limitations regarding sample geometry and optical transparency do not apply, which facilitates a transfer to well-established industrial technologies. Consequently, fiber-reinforced and highly filled magneto-active thiol-ene polymer composites are fabricated by a thermal curing approach. The on-demand activation of dynamic transesterification is demonstrated by (magneto-assisted) reshaping experiments, highlighting a wide range of potential future applications offered by the presented concept.