Thiol-ene Polymerization Research Articles

Thiol-ene polymer beads via liquid-liquid printing: armored interfaces and photopolymerization via graphitic carbon nitride.

Polymerization of multifunctional thiol-ene molecules is attractive as a proof of concept in photopolymerization, yet the formation of a bead structure is highly restricted. This manuscript will show graphitic carbon nitride based liquid–liquid printing and subsequent photopolymerization to form thiol-ene polymer beads with extreme simplicity and potential scalability.

Approaching new biomaterials: copolymerization characteristics of vinyl esters with norbornenes, allyl esters and allyl ethers

AbstractVinyl ester‐based monomers for radical photopolymerization have recently been shown to be promising alternatives to (meth)acrylates through lower irritancy and cytotoxicity. Vinyl ester monomers are becoming increasingly important on account of new, more cost‐efficient synthetic production methods, not to forget their increased reactivity and improved material properties in combination with thiol–ene polymerization. Due to their biocompatibility and degradability, these monomers are more frequently used in tissue engineering. Nevertheless, the material properties can be improved by possible copolymerizations with other monomers. Therefore, the copolymerization behavior of vinyl ester with norbornene, allyl ether and allyl ester has been studied fundamentally in a photoreactor via free radical photopolymerization. Here, the consumption of double bonds of the monomers has been identified using NMR spectroscopy. Copolymerization parameters have been determined using the Kelen–Tüdös method. Results show equal consumption of vinyl ester and co‐monomer double bonds leading to alternating copolymerizations. The double bond conversion was confirmed via in situ real‐time near‐infrared photorheology. Mono‐ and difunctional vinyl esters with co‐monomers have also provided further insight into the polymer network of these copolymers. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Antineoplastic activity of free 4-nitrochalcone and encapsulated in poly(thioether-ester) nanoparticles obtained by thiol-ene polymerization in two human leukemia cell lines (Jurkat and K562)

Poly(thioether-ester) (PTEe), a polymer synthesized from renewable monomers, is a promising alternative for the encapsulation of antitumor drugs due to its biocompatibility and biodegradability. Therefore, the aim of this study was to synthesize, characterize and evaluate the cytotoxicity of free 4-nitrochalcone (4NC) and 4NC encapsulated in PTEe nanoparticles prepared by thiol-ene miniemulsion polymerization in chronic myeloid leukemia in blast crisis (K562) and acute lymphoblastic leukemia (Jurkat) and peripheral blood mononuclear cells. 4NC was successfully encapsulated in PTEe nanoparticles with an encapsulation efficiency >90%, a mean size of 110 nm, negative surface charge and extended-release profile. Free 4NC and encapsulated in PTEe nanoparticles presented a significant cytotoxicity on K562 and Jurkat cells. Also, 4NC encapsulated in PTEe nanoparticles presented lower damage to peripheral blood mononuclear cells, providing a higher selectivity index than free 4NC for chronic myeloid leukemia in blast crisis (K562) and acute lymphoblastic leukemia (Jurkat). Considering the difficulties involved in leukemia treatment and good results obtained with free 4NC and encapsulated in PTEe nanoparticles, these results can be a new tool for the treatment of neoplastic cells.

Evaluation of the in vivo acute toxicity of poly(thioether-ester) and superparamagnetic poly(thioether-ester) nanoparticles obtained by thiol-ene miniemulsion polymerization.

Poly(thioether-ester) (PTEe) nanoparticles obtained by thiol-ene polymerization have received attention of many researchers due to several advantages, including, biocompatibility and biodegradability. The search for new nanomaterials requires toxicity studies to assess potential toxic effects of their administration. Therefore, the aim of this study was to evaluate the in vivo acute toxicity of PTEe and poly(thioether-ester)-coated magnetic nanoparticles prepared by thiol-ene polymerization in miniemulsion. These nanoparticles presented a mean size of approximately 120 nm, spherical morphology, and negative surface charge. Doses of 40 mg/kg were administered intraperitoneally to Swiss mice and nociceptive, behavioral and biochemical parameters were investigated in five different organs. None of the nanoparticles led to any alterations in the nociceptive and behavioral responses. Biochemical alterations were observed in liver, decreasing the sulfhydryl and glutathione (GSH) levels, suggesting the dependence of the GSH metabolism in the elimination of the nanoparticles. In general, both nanoparticle types did not cause disturbances in biochemical parameters analyzed in others organs. These results suggest that both nanoparticle types did not induce acute toxicity to the different organs evaluated, reinforcing the biocompatibility of PTEe nanoparticles synthetized by thiol-ene polymerization.

PeptiCHIP: A Microfluidic Platform for Tumor Antigen Landscape Identification.

Identification of HLA class I ligands from the tumor surface (ligandome or immunopeptidome) is essential for designing T-cell mediated cancer therapeutic approaches. However, the sensitivity of the process for isolating MHC-I restricted tumor-specific peptides has been the major limiting factor for reliable tumor antigen characterization, making clear the need for technical improvement. Here, we describe our work from the fabrication and development of a microfluidic-based chip (PeptiCHIP) and its use to identify and characterize tumor-specific ligands on clinically relevant human samples. Specifically, we assessed the potential of immobilizing a pan-HLA antibody on solid surfaces via well-characterized streptavidin–biotin chemistry, overcoming the limitations of the cross-linking chemistry used to prepare the affinity matrix with the desired antibodies in the immunopeptidomics workflow. Furthermore, to address the restrictions related to the handling and the limited availability of tumor samples, we further developed the concept toward the implementation of a microfluidic through-flow system. Thus, the biotinylated pan-HLA antibody was immobilized on streptavidin-functionalized surfaces, and immune-affinity purification (IP) was carried out on customized microfluidic pillar arrays made of thiol–ene polymer. Compared to the standard methods reported in the field, our methodology reduces the amount of antibody and the time required for peptide isolation. In this work, we carefully examined the specificity and robustness of our customized technology for immunopeptidomics workflows. We tested this platform by immunopurifying HLA-I complexes from 1 × 106 cells both in a widely studied B-cell line and in patients-derived ex vivo cell cultures, instead of 5 × 108 cells as required in the current technology. After the final elution in mild acid, HLA-I-presented peptides were identified by tandem mass spectrometry and further investigated by in vitro methods. These results highlight the potential to exploit microfluidics-based strategies in immunopeptidomics platforms and in personalized immunopeptidome analysis from cells isolated from individual tumor biopsies to design tailored cancer therapeutic vaccines. Moreover, the possibility to integrate multiple identical units on a single chip further improves the throughput and multiplexing of these assays with a view to clinical needs.

Utilizing direct-initiation of thiols for photoinitiator-free stereolithographic 3D printing of mechanically stable scaffolds

Abstract The automated production of artificial biological structures for biomedical applications continues to gather interest. Different fields of science are combined to find solutions for the arising multidimensional problems. Additive manufacturing in combination with material science provides one solution for the biological issues around 3D cell culture and construction of living tissues. Here, we present the photoinitiator-free stereolithographic fabrication of thiol-ene polymers with microarchitectures in the range of tens of microns for scaffolds up to the millimeter scale. Scaffolds composed of cubic unit cells were designed using computer-aided design (CAD) and subsequently 3D printed with a custom-made laser stereolithography setup. The process parameters were determined step by step with increasing complexity and number of parameters. Gained insights were applied to the fabrication of 3D printed test specimens. The quality of the 3D printed parts was evaluated by measuring the porosity and optical microscopy images. Furthermore, the mechanical properties of the scaffold structures were characterized using compression testing and compared with the bulk material revealing a lower capacity to bear load but higher flexibility. In this study, we demonstrate the advantages of combining the high-precision, freeform fabrication of stereolithography with a biocompatible material for the fabrication of complex microarchitectures for biomedical applications

Novel eugenol-based allyl-terminated precursors and their bio-based polymer networks through thiol-ene click reaction

The design of biobased allyl-terminated precursors with high renewable carbon content for the construction of the thiol-ene polymer networks is essential for sustainable development and green society. In this work, a series of allyl-terminated precursors were synthesized from renewable eugenol and aliphatic diols through a two-step procedure. Then, the alternating aliphatic-aromatic thiol-ene polymer networks with tunable flexibility, thermal and mechanical properties were constructed via solvent-free thiol-ene click photopolymerization. The results showed that the thermal-physical and mechanical properties of the resulting polymers improved with the decrease of the carbon length of the aliphatic diols and the increase of thiol functionality. The thiol-ene polymers exhibited high tensile strength of 22.12 MPa and elongation at break of 126 %. All the polymer networks are thermally stable without obvious weight loss (T5%) up to 270 °C. All the polymers exhibited excellent solvent resistance in alkaline solution, acid solution natural solution brine, water and ethanol solvent. This work successfully provided a facile and simple method to develop biobased ally compounds from eugenol and high-performance polymer networks with tunable performance.

Optical characterization and photo-electrical measurement of luminescent solar concentrators based on perovskite quantum dots integrated into the thiol-ene polymer

The luminescent solar concentrator (LSC) has attracted worldwide attention as a sunlight manager for harvesting solar energy in building integrated photovoltaic structures. However, until now the relatively low optical efficiency (ηopt) still severely hinders the advancement of the LSCs. In this work, we report the perovskite quantum dots (QDs) integrated into the thiol-ene polymer for LSC applications. After encapsulated by the thiol-ene polymer, the CsPbBr3 QDs exhibit a slight blue-shift of the PL peak position and increasing FWHM because of the dielectric screen effect. With the different QDs' concentrations from 8.3 × 10−3 to 2.5 × 10−2 mg/ml, the LSC performance is evaluated by the direct optical characterization and the indirect photo-electrical measurement in detail. After coupling the PV cells, the as-fabricated LSC shows the optimal optical efficiency of 2.11% and the power conversion efficiency of 1.06%.

Abstract 1897: PeptiCHIP: A novel microfluidic-based chip platform for tumor antigen landscape identification

Abstract Knowledge about naturally presented HLA class I ligands from the tumor surface (the ligandome or immunopeptidome) is essential for designing T-cell mediated cancer therapeutic approaches. Indeed, the generation of specific anti-tumor CD8+ T cells relies on the recognition of tumor-antigens in the HLA-I complex. However, the sensitivity of the process for isolating the tumor antigens have been the major limiting factor for reliable HLA-I peptide characterization, making clear the need for technical improvement.Here, we assessed the potential of immobilizing a pan-HLA antibody on solid surfaces via well-characterized streptavidin-biotin chemistry, overcoming the limitations of the cross-linking chemistry used to prepare the affinity matrix with the desired antibodies in the immunopeptidomic workflow. Furthermore, to address the restrictions related to the handling and the limited availability of tumor samples, we further developed the concept towards the implementation of a microfluidic through-flow system.Thus, the biotinylated pan-HLA antibody was immobilized on streptavidin-functionalized surfaces, and immune-affinity purification (IP) was carried out on customized microfluidic pillar arrays made of thiol-ene polymer. Compared to the standard methods reported in the field, our methodology drastically reduces the handling, the amount of antibody and the time required for peptide isolation.In this work, we carefully examined the specificity and robustness of our customized technology for immunopeptidomics workflows. We tested this novel platform by immunopurifying HLA-I complexes from as few as 106 cells both in a widely studied B-cell line and in patients-derived ex vivo cell cultures. After the final elution in mild acid, HLA-I-presented peptides were identified by tandem mass spectrometry and further investigated by in vitro methods. These results highlight the potential to exploit microfluidics-based strategies in immunopeptidomic platforms and in personalized immunopeptidome analysis from cells isolated from individual tumor biopsies to design tailored cancer therapeutic vaccines. Citation Format: Sara Feola, Markus Happala, Karita Peltonen, Cristian Capasso, Gabriella Antignani, Antonio Federico, Vilja Pietiäinen, Jacopo Chiaro, Michaela Feodoroff, Antti Ranniko, Manlio Fusciello, Satu Koskela, Jukka Partanen, Firas Hamdan, Sari Tähkä, Erkko Ylösmäki, Dario Greco, Mikaela Grönholm, Rui M M Branca, Janne Lehtiö, Tiina Siikanen, Vincenzo Cerullo. PeptiCHIP: A novel microfluidic-based chip platform for tumor antigen landscape identification [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1897.

The synthesis and characterization of polyorganosiloxane nanoparticles from 3-mercaptopropyltrimethoxysilane for preparation of nanocomposite films via photoinitiated thiol-ene polymerization.

This article describes the synthesis of modified silica nanoparticles (SiO2-MPTMS) via the condensation reaction carried out between silanol moieties of silica nanoparticles and the trialkoxy silyl groups of (3-mercaptopropyl) trimethoxysilane (MPTMS). Then, SiO2-MPTMS nanoparticles in certain amounts (0.5 wt %, 1 wt %, 2.5 wt % and 5 wt %) were incorporated into thiol-ene resins consisting of bisphenol A glycerolate dimethacrylate and trimethylolpropane tris(3-mercaptopropionate) to prepare nanocomposite films via the photoinitiated thiol-ene polymerization in presence of 2,2-Dimethoxy-2-phenylacetophenone 99% as a photoinitiator. Fourier transform infrared spectroscopy, dynamic light scattering, scanning transmission electron microscopy, thermal gravimetric analyzer, and X-ray photoelectron spectrometer were employed to characterize SiO2-MPTMS nanoparticles. It was revealed that the nanosilica surface was successfully grafted by MPTMS with the grafting ratio of 22.9%. Properties of the nanocomposite films such as decomposition temperature, thermal glass transition temperature, tensile strength, hardness, and particle distribution were investigated and the results were compared with each other and neat film. The addition of MPTMS-modified silica particles did not improve the thermal stability of the films. In scanning electron microscopy study, it was seen that 2.5 wt % of these nanoparticles used as additives were about 200 nm in size and dispersed homogeneously in the polymer matrix. The increase in tensile strength of nanocomposite films compared to the neat film was measured as 77.3% maximum.

Exploring the advantages of oxygen-tolerant thiol-ene polymerization over conventional acrylate free radical photopolymerization processes for pressure-sensitive adhesives

Exploring the advantages of oxygen-tolerant thiol-ene polymerization over conventional acrylate free radical photopolymerization processes for pressure-sensitive adhesives

Inkjet-printed flexible silver electrodes on thiol-enes

Flexible and conductive silver electrodes were fabricated by inkjet printing on several different compositions of thiol-ene polymers. Conductive electrodes with resistivity down to 30 μΩcm and good adhesion of the electrodes were obtained by optimizing the printing parameters. The maximum printing resolution was 100 μm lines and 80 μm gaps between the lines. Printing on top of cross-linked off-stoichiometric thiol-ene polymer was tested for compositions ranging from 30 % thiol excess to 5 % allyl (‘ene’) excess. The roughness off the thiol-ene surfaces was shown to greatly improve the quality of the printed electodes: consistently high yield of conductive electrodes was obtained on rough surfaces (roughness ≈ 1 μm), whereas on smooth surfaces the electrodes were often cracked. The lowest resistivity values were obtained on electrodes printed on near stoichiometric thiol-ene substrates. The conductivity of the electrodes was retained after 5 % linear strain and after repeated bending with 1 mm radius of curvature, showing the potential for flexible sensors. The electrodes were also applied to electrical impedance-based monitoring of cell growth on thiol-ene surfaces, which showcased that the electrodes survive stressed cell culture conditions for at least 36 h.

Developing Polymer Electrolytes with Balanced Thermomechanical and Conductive Properties through Incorporation of High Aromatic Content

Thermomechanical and electrochemical properties of thiol-ene polymers with high aromatic content afforded by lignocellulosic biomass were evaluated to explore feasibility and advantages in polymer electrolyte applications. Polymer electrolytes have the potential to mitigate stability and safety concerns accompanying incumbent liquid electrolyte systems in lithium-ion batteries. The thermal properties associated with low glass transition temperature (T g) polymers are thought to improve contact with electrodes and ionic flow through the membranes compared to other liquid electrolyte alternatives such as solid electrolytes. Additionally, the high aromatic content of the lignin macromolecule can impart mechanical and thermal stability, making it attractive for use in applications that require robust polymers.Low molecular weight fractions of wheat straw/Sarkanda grass soda lignin were functionalized and prepared through thiol-ene polymerization into polymer electrolytes. In combination with previous work, it was determined that differing solubility, functionality, and aromatic content of lignin fractions vary the glass transition temperatures of the resulting polymers and the suitability for electrolyte applications. The wheat straw/Sarkanda grass soda lignin utilized in solid polymer electrolytes (SPEs) displayed room temperature conductivity values in the range of 5 – 7 x 10-5 S cm-1. The lignin-based SPEs exhibited excellent cationic transport with ion transference values up to 0.90. Voltage stability and compatibility with electrode materials were also explored. The promising conductivity and ion transference results reveal the potential for use of functionalized, low molecular weight wheat straw/Sarkanda grass soda lignin in SPE applications as a way to improve thermal stability, electrochemical performance, and incorporate an abundant, sustainable resource in a high performance application.

Lung on a Chip Development from Off-Stoichiometry Thiol-Ene Polymer.

Current in vitro models have significant limitations for new respiratory disease research and rapid drug repurposing. Lung on a chip (LOAC) technology offers a potential solution to these problems. However, these devices typically are fabricated from polydimethylsiloxane (PDMS), which has small hydrophobic molecule absorption, which hinders the application of this technology in drug repurposing for respiratory diseases. Off-stoichiometry thiol–ene (OSTE) is a promising alternative material class to PDMS. Therefore, this study aimed to test OSTE as an alternative material for LOAC prototype development and compare it to PDMS. We tested OSTE material for light transmission, small molecule absorption, inhibition of enzymatic reactions, membrane particle, and fluorescent dye absorption. Next, we microfabricated LOAC devices from PDMS and OSTE, functionalized with human umbilical vein endothelial cell (HUVEC) and A549 cell lines, and analyzed them with immunofluorescence. We demonstrated that compared to PDMS, OSTE has similar absorption of membrane particles and effect on enzymatic reactions, significantly lower small molecule absorption, and lower light transmission. Consequently, the immunofluorescence of OSTE LOAC was significantly impaired by OSTE optical properties. In conclusion, OSTE is a promising material for LOAC, but optical issues should be addressed in future LOAC prototypes to benefit from the material properties.

Non-aqueous electrophoresis integrated with electrospray ionization mass spectrometry on a thiol-ene polymer-based microchip device.

Non-aqueous capillary electrophoresis (NACE) on microfluidic chips is still a comparatively little explored area, despite the inherent advantages of this technique and its application potential for, in particular, lipophilic compounds. A main reason is probably the fact that implementation of NACE on microchips largely precluded the use of polymeric substrate materials. Here, we report non-aqueous electrophoresis on a thiol-ene-based microfluidic chip coupled to mass spectrometry via an on-chip ESI interface. Microchips with an integrated ESI emitter were fabricated using a double-molding approach. The durability of thiol-ene, when exposed to different organic solvents, was investigated with respect to swelling and decomposition of the polymer. Thiol-ene exhibited good stability against organic solvents such as methanol, ethanol, N-methylformamide, and formamide, which allows for a wide range of background electrolyte compositions. The integrated ESI emitter provided a stable spray with RSD% of the ESI signal ≤8%. Separation efficiency of the developed microchip electrophoresis system in different non-aqueous buffer solutions was tested with a mixture of several drugs of abuse. Ethanol- and methanol-based buffers provided comparable high theoretical plate numbers (≈ 6.6 × 104-1.6 × 105m-1) with ethanol exhibiting the best separation efficiency. Direct coupling of non-aqueous electrophoresis to mass spectrometry allowed for fast analysis of hydrophobic compounds in the range of 0.1-5μgmL-1 and 0.2-10μgmL-1 and very good sensitivities (LOD ≈ 0.06-0.28μgmL-1; LOQ ≈ 0.20-0.90μgmL-1). The novel combination of non-aqueous CE on a microfluidic thiol-ene device and ESI-MS provides a mass-producible and highly versatile system for the analysis of, in particular, lipophilic compounds in a wide range of organic solvents. This offers promising potential for future applications in forensic, clinical, and environmental analysis. Graphical abstract.

In Vitro Degradation and Cytotoxicity Response of Biobased Nanoparticles Prepared by Thiol-ene Polymerization in Miniemulsion

Biodegradability is a key feature for the application of polymeric devices in medicine. This study reports an experimental and theoretical study of the degradation of poly(thioether-ester) (PTEe) nanoparticles in aqueous media. The α,ω-diene diester derived from vegetable oil, 1,3-propylene diundeca-10-polenoate (Pd10e), was used as monomer in the solvent-free synthesis of Pd10e-based nanoparticles (A-PTEe nanoparticles) via thiol-ene miniemulsion polymerization. The theoretical partition coefficients of A-PTEe and a PTEe based on dianhydro-d-glucityl diundec-10-enoate (DGU) (B-PTEe nanoparticles) were calculated using density functional theory (DFT), in order to compare their degradation behavior. The results showed that A-PTEe is more hydrophilic than B-PTEe, thus indicating the possible faster degradation of the former. The experimental degradation studies showed that, in fact, A-PTEe nanoparticles are faster degraded than B-PTEe, presenting substantial molecular weight decrease, which confirms the theoretical results. The effects of degradation could be observed in the chemical composition and thermal properties of the polymer. Considering its applicability potential as a biomaterial due to its fast degradation behavior, the cytotoxicity of A-PTEe nanoparticles and its degradation products were evaluated. In vitro assays confirmed the biocompatibility of A-PTEe nanoparticles and its degradation products when exposed on fibroblasts and red blood cells. These results suggest A-PTEe nanoparticles can be promising candidates as biobased nanocarriers for biomedical applications.

Facile preparation of thioether/hydroxyl functionalized polyhedral oligomeric silsesquioxanes hybrid polymer for ultrahigh selective adsorption of silver(I) ions

It is a difficult task to remove Ag(I) ions selectively from the complex wastewater containing low concentration of silver(I) ions and high concentration of interfering ions. In this work, the polyhedral oligomeric silsesquioxanes (POSS) hybrid polymer (PSDT) functionalized with thioether/hydroxyl groups was facilely synthesized by photo-initiated thiol-ene polymerization of vinylPOSS and 1, 4-dithiothreitol. The PSDT showed ultrahigh selectivity to Ag(I) ions in a wide pH range, which could completely remove trace level of Ag(I) ions (1 mg L−1) from the complex wastewater containing concentrated interfering ions such as Pb(II), Cu(II), Ni(II), Zn(II), Ca(II) and Fe(III) ions (each 200 mg L−1), nevertheless, those interfering ions were hardly adsorbed on the PSDT polymer. Moreover, the maximum adsorption capacity for Ag(I) by PSDT was 303 mg g−1 at pH 0.5, and the distribution coefficient (Kd) for Ag(I) ions could reach 1,620,000 mL g−1, which was significantly greater than most of the adsorbent materials reported. The high sulfur content (5.93 mmol g−1) of nanostructured PSDT and the formation of a stable five-membered Ag(I)-chelated ring may be the major causes for the ultrahigh selective adsorption of Ag(I) ions by PSDT.

Enhanced properties of well-defined polymer networks prepared by a sequential thiol-Michael - radical thiol-ene (STMRT) strategy

A sequential thiol-Michael - radical thiol-ene (STMRT) strategy was used to produce poly(ethylene glycol)-based model networks and enable establishment of a structure–property relationship from the network characteristics. Selective double thiol-Michael reactions on a series of poly(ethylene glycol) diacrylates (PEGDA), that differed in average chain length, with two molar equivalents of the trithiol trimethylolpropane tris(3-mercaptopropionate) (TMPTMP) yielded well-defined telechelic poly(ethylene glycol)-based tetrathiols. These tetrathiols were in turn used to produce model (co–)networks by photo-induced radical thiol-ene polymerization with either the same poly(ethylene glycol) diacrylates or with tri(ethyleneglycol) divinylether (TEGDVE). The properties of these networks were studied by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The STMRT-produced model networks possess storage moduli (E′) up to 4-fold larger and glass transition temperatures (Tg) of up to 10 °C lower than conventionally produced counterparts. The STMRT strategy allows the properties of the model networks to be finely tuned by manipulation of crosslink density and average polymer chain length.

Response surface design of a thiol-ene polymer sealant to model adhesive strength

Commercial aircraft fuel tanks require sealants applied at contact points to prevent leakage or moisture contamination, but cure times for conventional sealants range from hours to days. Thiol-ene ultraviolet (UV) curable sealants have been a proposed material for these applications. However, selecting proper monomers and optimizing synthesis conditions for a figure of merit is an arduous process. Therefore, modeling the adhesive strength of a thiol-ene sealant was performed using a response surface design of experiment (DoE). Two separate crosslinking alkenes were separately combined with a thiol monomer, and a 6 mm thick polymer was synthesized at different cure temperatures, cure times, and with various solid filler material on an aluminum substrate according to a response surface design. The samples were then peeled off the substrate at a 180° angle, and peel strength was measured. The DoE utilized the peel data to derive a multivariable numeric function for the peel strength. Resulting contour data shows the system has not been fully optimized, but trends in the data show that future experiments should lean toward higher cure times and temperatures to maximize peel strength. Additionally, the resulting model equation can predict adhesive strengths near the studied conditions.

Vegetable Oil-Based Thiol-Ene/Thiol-Epoxy Resins for Laser Direct Writing 3D Micro-/Nano-Lithography.

The use of renewable sources for optical 3D printing instead of petroleum-based materials is increasingly growing. Combinations of photo- and thermal polymerization in dual curing processes can enhance the thermal and mechanical properties of the synthesized thermosets. Consequently, thiol-ene/thiol-epoxy polymers were obtained by combining UV and thermal curing of acrylated epoxidized soybean oil and epoxidized linseed oil with thiols, benzene-1,3-dithiol and pentaerythritol tetra(3-mercaptopropionate). Thiol-epoxy reaction was studied by calorimetry. The changes of rheological properties were examined during UV, thermal and dual curing to select the most suitable formulations for laser direct writing (LDW). The obtained polymers were characterized by dynamic-mechanical thermal analysis, thermogravimetry, and mechanical testing. The selected dual curable mixture was tested in LDW 3D lithography for validating its potential in optical micro- and nano-additive manufacturing. The obtained results demonstrated the suitability of epoxidized linseed oil as a biobased alternative to bisphenol A diglycidyl ether in thiol-epoxy thermal curing reactions. Dual cured thermosets showed higher rigidity, tensile strength, and Young’s modulus values compared with UV-cured thiol-ene polymers and the highest thermal stability from all prepared polymers. LDW results proved their suitability for high resolution 3D printing—individual features reaching an unprecedented 100 nm for plant-based materials. Finally, the biobased resin was tested for thermal post-treatment and 50% feature downscaling was achieved.