Synthesis, insecticidal activity, and ensembled docking of nitroguanidines bearing S- and R-proline.

BACKGROUND: The amino acids R- and S-proline were used to synthesize novel neonicotinoid derivatives that, after being characterized by 1 H, DEPTQ 135, and HRMS-QTOF, were evaluated for use as insecticides against Galleria mellonella (caterpillar), Sitophilus zeamais, Xylosandrus morigerus, Xyleborus affinis, and Xyleborus ferrugineus. RESULTS: Comparisons of biological activity and absolute configuration showed that the R enantiomer had excellent and outstanding insecticidal activity against the insects tested, with up to 100% mortality after 12 h compared with dinotefuran at the same concentration. CONCLUSIONS: The results suggest that compound R6 is an excellent lead enantiopure insecticide for future development in the field of crop protection. Furthermore, intermolecular interactions between nicotinic acetylcholine receptors and the R enantiomer displays a lower score which mean a higher affinity to the nAChR receptor and the π-π interactions are more stable than the S derivative. © 2023 Society of Chemical Industry.

Development of Biodegradable Polyesters: Study of Variations in Their Morphological and Thermal Properties through Changes in Composition of Alkyl-Substituted (ε-DL) and Non-Substituted (ε-CL, EB, L-LA) Monomers.

Three series of polyesters based on monomer combinations of ε-caprolactone (ε-CL), ethylene brassylate (EB), and l-Lactide (LLA) with the alkyl substituted lactone ε-decalactone (ε-DL) were synthesized at different molar ratios. Copolymers were obtained via ring opening polymerization (ROP) employing TBD (1,5,7-triazabicyclo-[4.4.0]-dec-5-ene), an organic catalyst which can be handled under normal conditions, avoiding the use of glove box equipment. The molar monomer composition of resulting copolymers differed from theoretical values due to lower ε-DL reactivity; their Mn and Mw values were up to 14 kDa and 22.8 kDa, respectively, and distributions were (Ɖ) ≤ 2.57. The thermal stability of these materials suffered due to variations in their ε-DL molar content. Thermal transitions such as melting (Tm) and crystallization (Tc) showed a decreasing tendency as ε-DL molar content increased, while glass transition (Tg) exhibited minor changes. It is worth mentioning that changes in monomer composition in these polyesters have a strong impact on their thermal performance, as well as in their crystallization degree. Consequently, variations in their chemical structure may have an effect on hydrolyic degradation rates. It should be noted that, in future research, some of these copolymers will be exposed to hydrolytic degradation experiments, including characterizations of their mechanical properties, to determine their adequacy in potential use in the development of soft medical devices.

Biomimetic Synthesis of PANI/Graphitic Oxidized Carbon Nitride for Supercapacitor Applications.

Polyaniline (PANI) composites have gained momentum as supercapacitive materials due to their high energy density and power density. However, some drawbacks in their performance remain, such as the low stability after hundreds of charge-discharge cycles and limitations in the synthesis scalability. Herein, we report for the first time PANI-Graphitic oxidized carbon nitride composites as potential supercapacitor material. The biomimetic polymerization of aniline assisted by hematin, supported by phosphorous and oxygen-modified carbon nitrides (g-POCN and g-OCN, respectively), achieved up to 89% yield. The obtained PAI/g-POCN and PANI/g-OCN show enhanced electrochemical properties, such as conductivity of up to 0.0375 S/cm, specific capacitances (Cs) of up to 294 F/g (at high current densities, 5 A/g) and a stable operation after 500 charge-discharge cycles (at 3 A/g). In contrast, the biomimetic synthesis of Free PANI, assisted by stabilized hematin in cosolvents, exhibited lower performance properties (65%). Due to their structural differences, the electrochemical properties of Free PANI (conductivity of 0.0045 S/cm and Cs of up to 82 F/g at 5 A/g) were lower than those of nanostructured PANI/g-POCN and g-OCN supports, which provide stability and improve the properties of biomimetically synthesized PANI. This work reveals the biomimetic synthesis of PANI, assisted by hematin supported by modified carbon nitrides, as a promising strategy to produce nanostructured supercapacitors with high performance.

Synthesis of copolyesters based on substituted and non-substituted lactones towards the control of their crystallinity and their potential effect on hydrolytic degradation in the design of soft medical devices.

A series of copolymers based on ε-caprolactone (ε-CL) in combination with lactone monomers substituted with alkyl groups (4 and 6 carbon atoms), specifically δ-decalactone (δ-DL), ε-decalactone (ε-DL) and δ-dodecalactone (δ-DD), as well as a copolymer using two substituted lactone monomers with alkyl groups (ε-DL and δ-DD) were synthesized in different molar ratios. The objective of the synthesis of these copolymers was to evaluate the effects of branching in the polymer backbone on the crystallinity and the thermal properties of the synthesized materials. All copolymers were obtained via ring-opening polymerization with high conversion values for both comonomers using neodymium isopropoxide (Nd(i-Pr)3) as the initiator, and their compositions were determined by 1H NMR and 13C NMR. The molar masses (M n and M w) and distributions were obtained by GPC measurements. Such measurements showed that a majority of the copolymers exhibited dispersities (Ɖ) in the range of 1.2-1.6 and M n in the range of 15-40 kDa. First- and second-order transitions such as melting, crystallization and glass transition, as well as the crystallization degree (melting enthalpy), were determined by DSC analysis. Copolymers based on ε-CL developed interesting behaviors, wherein the copolymers with higher percentages of this monomer exhibited semicrystalline behavior, while the copolymers with a higher percentage of the comonomers ε-DL, δ-DL or δ-DD showed amorphous behavior. In contrast, the copolymers synthesized using both monomers from the alkyl group-substituted lactone developed fully amorphous features, regardless of their composition. These changes in the crystalline features of the synthesized copolymers suggest that the content of short branchings on the copolymer backbone will significantly modify their rates of hydrolytic degradation and their potential use in the development of different soft medical devices.

A Comparative Study of Biomimetic Synthesis of EDOT-Pyrrole and EDOT-Aniline Copolymers by Peroxidase-like Catalysts: Towards Tunable Semiconductive Organic Materials.

It has been two decades since biomimetic synthesis of conducting polymers were first reported, however, the systematic investigation of how catalysts influence the properties of the conducting polymers has not been reported yet. In this paper, we report a comparative study between peroxidase-like catalyst, dopants, and their effect on the properties of poly (3,4-ethylenedioxythiophene) (PEDOT), polypyrrole (PPY), and polyaniline (PANI). We also investigate the EDOT-Pyrrole and EDOT-Aniline copolymerization by enzymomimetic synthesis using two catalysts (Ferrocene and Hematin). It was found that, chemically, there are no detectable effects, only having small contributions in molar ratios greater than 0.7-0.3. Spectroscopic data provide solid evidence concerning the effect in the variation of the molar fractions, finding that, as the molar fraction of EDOT decreases, changes associated with loss of the conjugation of the structure and the oxidation state of the chains were observed. The electrical conductivity was considerably modified depending on the type of catalyst. Hematin produces conductive homopolymers and copolymers when doped with p-toluene sulfonic acid (TSA), while ferrocene produces low conductive copolymers under the same conditions. The mole fraction affects conductivity significantly, showing that as the EDOT fraction decreases, the conductivity drops drastically for both EDOT-PY and EDOT-ANI copolymers. The type of dopant also notably affects conductivity; the best values were obtained by doping with TSA, while the lowest were obtained when doping with polystyrene sulfonate (PSS). We also draw a biomimetic route to tailor the fundamental properties of conducting homopolymers and copolymers for their design and scaled-up production, as they have recently been found to have use in a broad range of applications.

Coordinative Chain Transfer Polymerization of Sustainable Terpene Monomers Using a Neodymium-Based Catalyst System.

The present investigation involves the coordinative chain transfer polymerization (CCTP) of biobased terpenes in order to obtain sustainable polymers from myrcene (My) and farnesene (Fa), using the ternary Ziegler-Natta catalyst system comprising [NdV3]/[Al(i-Bu)2H]/[Me2SiCl2] and Al(i-Bu)2H, which acts as cocatalyst and chain transfer agent (CTA). The polymers were produced with a yield above 85% according to the monomeric consumption at the end of the reaction, and the kinetic examination revealed that the catalyst system proceeded with a reversible chain transfer mechanism in the presence of 15-30 equiv. of CTA. The resulting polyterpenes showed narrow molecular weight distributions (Mw/Mn = 1.4-2.5) and a high percent of 1,4-cis microstructure in the presence of 1 equiv. of Me2SiCl2, having control of the molecular weight distribution in Ziegler-Natta catalytic systems that maintain a high generation of 1,4-cis microstructure.

Terpene Coordinative Chain Transfer Polymerization: Understanding the Process through Kinetic Modeling.

The interest in the Coordinative Chain Transfer Polymerization (CCTP) of a family of naturally occurring hydrocarbon monomers, namely terpenes, for the production of high-performance rubbers is increasing year by year. In this work, the synthesis of poly(ß-myrcene) via CCTP is introduced, using neodymium versatate (NdV3), diisobutylaluminum hydrade (DIBAH) as the catalytic system and dimethyldichlorosilane (Me2SiCl2) as the activator. A bimodal distribution in the GPC signal reveals the presence of two populations at low conversions, attributable to dormants (arising from reversible chain transfer reactions) and dead chains (arising from termination and irreversible chain transfer reactions); a unimodal distribution is generated at medium and high conversions, corresponding to the dominant species, the dormant chains. Additionally, a mathematical kinetic model was developed based on the Method of Moments to study a set of selected experiments: ([ß-myrcene]0:[NdV3]0:[DIBAH]0:[Me2SiCl2]0 = 660:1:2:1, 885:1:2:1, and 533:1:2:1). In order to estimate the kinetic rate constant of the systems, a minimization of the sum of squared errors (SSE) between the model predicted values and the experimental measurements was carried out, resulting in an excellent fit. A set of the Arrhenius parameters were estimated for the ratio [ß-myrcene]0:[NdV3]0:[DIBAH]0:[Me2SiCl2]0 = 660:1:2:1 in a temperature range between 50 to 70 °C. While the end-group functionality (EGF) was predominantly preserved as the ratio [ß-myrcene]0:[NdV3]0 was decreased, higher catalytic activity was obtained with a high ratio.

Evaluation of the Antimicrobial, Thermal, Mechanical, and Barrier Properties of Corn Starch-Chitosan Biodegradable Films Reinforced with Cellulose Nanocrystals.

Packaging materials play an essential role in the preservation and marketing of food and other products. To improve their conservation capacity, antimicrobial agents that inhibit bacterial growth are used. Biopolymers such as starch and chitosan are a sustainable alternative for the generation of films for packaging that can also serve as a support for preservatives and antimicrobial agents. These substances can replace packaging of synthetic origin and maintain good functional properties to ensure the quality of food products. Films based on a mixture of corn starch and chitosan were developed by the casting method and the effect of incorporating cellulose nanocrystals (CNC) at different concentrations (0 to 10% w/w) was studied. The effect of the incorporation of CNC on the rheological, mechanical, thermal and barrier properties, as well as the antimicrobial activity of nanocomposite films, was evaluated. A significant modification of the functional and antimicrobial properties of the starch-chitosan films was observed with an increase in the concentration of nanomaterials. The films with CNC in a range of 0.5 to 5% presented the best performance. In line with the physicochemical characteristics which are desired in antimicrobial materials, this study can serve as a guide for the development this type of packaging for food use.

Synthesis and Vulcanization of Polymyrcene and Polyfarnesene Bio-Based Rubbers: Influence of the Chemical Structure over the Vulcanization Process and Mechanical Properties.

The overuse of fossil-based resources to produce thermoplastic materials and rubbers is dramatically affecting the environment, reflected in its clearest way as global warming. As a way of reducing this, multiple efforts are being undertaken including the use of more sustainable alternatives, for instance, those of natural origin as the main feedstock alternative, therefore having a lower carbon footprint. Contributing to this goal, the synthesis of bio-based rubbers based on ß-myrcene and trans-ß-farnesene was addressed in this work. Polymyrcene (PM) and polyfarnesene (PF) were synthesized via coordination polymerization using a neodymium-based catalytic system, and their properties were compared to the conventional polybutadiene (PB) and polyisoprene (PI) also obtained via coordination polymerization. Moreover, different average molecular weights were also tested to elucidate the influence over the materials' properties. The crosslinking of the rubbers was carried out via conventional and efficient vulcanization routes, comparing the final properties of the crosslinking network of bio-based PM and PF with the conventional fossil-based PB and PI. Though the mechanical properties of the crosslinked rubbers improved as a function of molecular weight, the chemical structure of PM and PF (with 2 and 3 unsaturated double bonds, respectively) produced a crosslinking network with lower mechanical properties than those obtained by PB and PI (with 1 unsaturated double bond). The current work contributes to the understanding of improvements (in terms of crosslinking parameters) that are required to produce competitive rubber with good sustainability/performance balance.

Controlled (Co)Polymerization of Methacrylates Using a Novel Symmetrical Trithiocarbonate RAFT Agent Bearing Diphenylmethyl Groups.

Herein, we report a novel type of symmetrical trithiocarbonate chain transfer agent (CTA) based diphenylmethyl as R groups. The utilization of this CTA in the Reversible Addition-Fragmentation chain Transfer (RAFT) process reveals an efficient control in the polymerization of methacrylic monomers and the preparation of block copolymers. The latter are obtained by the (co)polymerization of styrene or butyl acrylate using a functionalized macro-CTA polymethyl methacrylate (PMMA) previously synthesized. Data show low molecular weight dispersity values (D < 1.5) particularly in the polymerization of methacrylic monomers. Considering a typical RAFT mechanism, the leaving groups (R) from the fragmentation of CTA should be able to re-initiate the polymerization (formation of growth chains) allowing an efficient control of the process. Nevertheless, in the case of the polymerization of MMA in the presence of this symmetrical CTA, the polymerization process displays an atypical behavior that requires high [initiator]/[CTA] molar ratios for accessing predictable molecular weights without affecting the D. Some evidence suggests that this does not completely behave as a common RAFT agent as it is not completely consumed during the polymerization reaction, and it needs atypical high molar ratios [initiator]/[CTA] to be closer to the predicted molecular weight without affecting the D. This work demonstrates that MMA and other methacrylic monomers can be polymerized in a controlled way, and with "living" characteristics, using certain symmetrical trithiocarbonates.

Surface Modification of Cellulose Nanocrystals with Lactone Monomers via Plasma-Induced Polymerization and Their Application in ABS Nanocomposites.

The growing concern for environmental problems has motivated the use of materials obtained from bio-based resources such as cellulose nanocrystals which have a promising application acting as fillers or reinforcements of polymeric materials. In this context, in this article, plasma-induced polymerization is proposed as a strategy to modify nanocrystals at different plasma power intensities using ε-caprolactone and δ-decalactone to improve their compatibility with polymeric matrices. The characterization was carried out using techniques such as FTIR, TGA, XRD, XPS, and AFM, with which a successful functionalization was demonstrated without altering the inherent properties of the nanocrystals. The preparation of ABS nanocomposites was carried out with the modified nanoparticles and the evaluation of the mechanical properties indicates an increase in Young's modulus and yield stress under certain concentrations of modified cellulose nanocrystals.

Fully Bio-Based Elastomer Nanocomposites Comprising Polyfarnesene Reinforced with Plasma-Modified Cellulose Nanocrystals.

This article proposes a process to prepare fully bio-based elastomer nanocomposites based on polyfarnesene and cellulose nanocrystals (CNC). To improve the compatibility of cellulose with the hydrophobic matrix of polyfarnesene, the surface of CNC was modified via plasma-induced polymerization, at different powers of the plasma generator, using a trans-ß-farnesene monomer in the plasma reactor. The characteristic features of plasma surface-modified CNC have been corroborated by spectroscopic (XPS) and microscopic (AFM) analyses. Moreover, the cellulose nanocrystals modified at 150 W have been selected to reinforce polyfarnesene-based nanocomposites, synthesized via an in-situ coordination polymerization using a neodymium-based catalytic system. The effect of the different loading content of nanocrystals on the polymerization behavior, as well as on the rheological aspects, was evaluated. The increase in the storage modulus with the incorporation of superficially modified nanocrystals was demonstrated by rheological measurements and these materials exhibited better properties than those containing pristine cellulose nanocrystals. Moreover, we elucidate that the viscoelastic moduli of the elastomer nanocomposites are aligned with power-law model systems with characteristic relaxation time scales similar to commercial nanocomposites, also implying tunable mechanical properties. In this foreground, our findings have important implications in the development of fully bio-based nanocomposites in close competition with the commercial stock, thereby producing alternatives in favor of sustainable materials.

l-Proline as a Valuable Scaffold for the Synthesis of Novel Enantiopure Neonicotinoids Analogs.

In this research, six neonicotinoid analogs derived from l-proline were synthesized, characterized, and evaluated as insecticides against Xyleborus affinis. Most of the target compounds showed good to excellent insecticidal activity. To the best of our knowledge, this is the first report dealing with the use of enantiopure l-proline to get neonicotinoids. These results highlighted the compound 9 as an excellent candidate used as the lead chiral insecticide for future development. Additionally, molecular docking with the receptor and compound 9 was carried out to gain insight into its high activity when compared to dinotefuran. Finally, the neurotoxic evaluation of compound 9 showed lower toxicity than the classic neonicotinoid dinotefuran.

Plasma surface-modification of cellulose nanocrystals: a green alternative towards mechanical reinforcement of ABS.

This article proposes a strategy to functionalize cellulose nanocrystals by means of plasma-surface modification utilizing monomers of different nature: caprolactone, styrene and farnesene. The surface characteristics of the nanocrystals were studied by different techniques including XPS, FTIR and STEM, demonstrating that this technique allows a successful functionalization, yielding homogenous functionalization which does not alter the rod-like shape of the nanocrystals, and therefore their anisotropic behavior. We have furthermore studied the employment of the modified nanocrystals as reinforcement additive of ABS, which significantly enhanced the impact resistance of the thermoplastic, which could have great implications for industrial applications.

Resonance properties of Ag-ZnO nanostructures at terahertz frequencies.

Nanoantennas have been fabricated by scaling down traditional antenna designs using nanolithographic techniques and testing them at different optical wavelengths, these particular nanoantennas have shown responses in a broad range of frequencies going from visible wavelengths to the range of the terahertz. Some self-assembled nanostructures exist that exhibit similar shapes and properties to those of traditional antenna structures. In this work the emission and absorption properties of self-assembled nanostructures made of zinc oxide nanorods on silver nanowires, which resemble traditional dipole antennas, were measured and simulated in order to test their antenna performance. These structures show resonant properties in the 10-120 THz range, with the main resonance at 60 THz. The radiation pattern of these nanostructures was also obtained by numerical simulations, and it is shown that it can be tailored to increase or decrease its directivity as a function of the location of the energy source of excitation. Experimental measurements were performed by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR) in order to show existing vibrational frequencies at the resonant frequencies of the nanostructures, measurements were made from ~9 to 103 THz and the results were in agreement with the simulations. These characteristics make these metal-semiconductor Ag/ZnO nanostructures useful as self-assembled nanoantennas in applications such as terahertz spectroscopy and sensing at terahertz frequencies.

Seebeck nanoantennas for the detection and characterization of infrared radiation.

Arrays of metallic thermocouples in the shape of spiral nanoantennas are proposed as infrared detectors, which use the thermoelectric properties of the metallic interfaces to generate electrical DC signals. The responsivity of these types of antennas is evaluated from both theoretical and numerical perspectives pointing out its potential as infrared sensors. Moreover, the same structures can be used to characterize the state of polarization of the optical near fields with a spatial resolution comparable to the wavelength.