Ring-opening Addition Reaction Research Articles

Qualitative and quantitative analysis of electrons donated by pollutants in electron transfer-based oxidation system: Electrochemical measurement and theoretical calculations

In order to gain a profound understanding of the fate of pollutants in advanced oxidation processes (AOPs), this study analyzed the electron contribution of pollutants qualitatively and quantitatively which rarely reported before. The rich electron transfer system was constructed by mesoporous carbon nitride (MCN) coupling with persulfate (PS) driven by visible light and the sulfanilamide antibiotics (SULs) were used as target contaminants. Firstly, the qualitative analysis of electron transfer in the system was confirmed systematically. The electron flow direction tested by i-t curves indicated that PS absorbed electrons, while SULs released electrons. The flow rate of electrons was also accelerated after the addition of SULs. The fitting curve between the kinetics and the peak potential difference tested by CV curve showed that the larger potential difference, the slower rate of oxidative degradation. Secondly, the quantification of electron transfer was achieved through theoretical calculations to simulate the interactions of the ‘catalyst-oxidant-antibiotic’ system. After the addition of SULs, the adsorption energy of the ‘catalyst-oxidant-antibiotic’ system was enhanced and the bond length of the peroxide bond was stretched. Notably, the electron transfer analysis results showed that the charge of SULs was around 0.032–0.056e, indicating that SULs pollutants played the role of electron contributors in the system. The oxidative degradation pathway included the direct cracking of S-N bond, shedding of marginal groups, ring-opening and hydroxyl addition reaction. This study clarified the electronic contribution of SULs in the oxidation system, providing necessary theoretical supplement for the analysis of the transformation of pollutants in AOPs.

Novel Environmentally Responsive Polyvinyl Polyamine Hydrogels Capable of Phase Transformation with Temperature for Applications in Reservoir Profile Control.

Hydrogel has been widely used in reservoir regulation for enhancing oil recovery, however, this process can experience negative influences on the properties and effects of the hydrogels. Therefore, developing novel hydrogels with excellent environmental responsiveness would improve the formation adaptability of hydrogels. In this study, novel polyvinyl polyamine hydrogels were synthesized by a ring-opening addition reaction between polyvinyl polyamines and polyethylene glycol glycidyl ether. The results of atomic force microscopy and transmission electron microscopy showed that the polyvinyl polyamine gel had a porous and irregular bulk structure and was endowed with water storage. With the temperature rising from 30 °C to 60 °C, the transmittance of diethylenetriamine hydrogel decreased from 84.3% to 18.8%, indicating that a phase transition had occurred. After the polyvinyl polyamine hydrogel with low initial viscosity was injected into the formation in the liquid phase, the increase of the reservoir temperature caused it to turn into an elastomer, thereby migrating to the depth of the reservoir and achieving effective plugging. Polyvinyl polyamine hydrogel could improve the profile of heterogeneous layers significantly by forcing subsequent fluids into the low permeability zone in the form of elastomers in the medium temperature reservoirs of 40-60 °C. The novel environmentally responsive polyvinyl polyamine hydrogels, capable of phase transformation with temperature, exhibited superior performance in recovering residual oil, which was beneficial for applications in reservoir profile control and oilfield development.

Cationic amino-acid functionalized polymethacrylamide vectors for siRNA transfection based on modification of poly(2-isopropenyl-2-oxazoline)

Poly(2-isopropenyl-2-oxazoline) (PiPOx) is a functional polymer showing great potential for the development of smart biomaterials. The straightforward synthesis and post-polymerization functionalization of PiPOx offers many opportunities for tailoring the properties of the polymer towards biomaterials. In this study we report for the first time PiPOx-based cationic charged polymethacrylamides with amino acid side chains that can complex siRNA and promote transfection in vitro. Therefore, PiPOx was fully modified via ring opening addition reactions with the carboxylic acid groups of a series of N-Boc-L-amino acids and their reaction kinetics were investigated. Based on the determined kinetic constants, another series of PiPOx-based copolymers with balanced hydrophilic/hydrophobic content of N-Boc-L-amino acids were obtained via one-pot modification reaction with two different N-Boc-L-amino acids. The N-Boc protected homopolymers and related copolymers were deprotected to obtain (co)polymers with the targeted side chain cationic charged units. The (co)polymers' structures were fully investigated via FT-IR and 1H NMR spectroscopy, size exclusion chromatography (SEC), and TGA–DSC–MS analysis. The polarimetry measurements revealed that the homopolymers retain their chiroptical properties after post-modification, and a sign inversion is noticed from (L) N-Boc-protected analogues to (D) for the TFA cationic charged homopolymers. Generally, cationically charged homopolymers with hydrophilic amino acids on the side chain showed efficient complexation of siRNA, but poor transfection while cationic copolymers having both tryptophan and valine or proline side chains revealed moderate siRNA binding, high transfection efficiency (> 90% of the cells) and potent gene silencing with IC50 values down to 5.5 nM. Particularly, these cationic copolymers showed higher gene silencing potency as compared to the commercial JetPRIME® reference, without reducing cell viability in the concentration range used for transfection, making this a very interesting system for in vitro siRNA transfection.

Phosphine-Catalyzed Stereoselective Ring-Opening Addition of Cyclopropenones with Nucleophiles.

A phosphine-catalyzed ring-opening addition reaction of cyclopropenones with a variety of nucleophiles (NuH), including oxygen-, nitrogen-, sulfur-, and carbon-based ones, has been investigated, which produces potentially useful α,β-unsaturated carbonyl derivatives in high yields (up to 99%), high regioselectivity, and exclusive E-selectivity. The reaction proceeds in high efficiency under very mild conditions using only 1 mol % PPh3 as the catalyst at room temperature. The method is also amenable for the synthesis of deuterated alkenes when deuterated nucleophiles (NuD) are employed. The mechanism is investigated by experiments and DFT calculations, which suggests an α-ketenyl phosphorus ylide as a key intermediate in the catalytic cycle that captures the nucleophiles in a stereoselective manner.

A sustainable and reactive intumescent flame-retardant containing phytate and triazine-trione for durable functional coating of silk fabric

The development of sustainable, efficient and durable flame-retardant (FR) coating for silk fabric using plant-derived phytic acid is of great interest. This work synthesized a novel and reactive intumescent FR agent namely glycidyl phytate isocyanurate (GPIC) through ring-opening addition reaction using phytic acid and 1,3,5-triglycidyl isocyanurate. Then, the durable FR coated silk fabric was developed with GPIC through the surface coating route. The chemical structure of GPIC, and its cross-linking mechanism with silk, the smoke and heat generation performance, flame retardancy and washing durability of coated silk were studied. The coated silk fabric with a weight gain of 13.6 % could self-extinguish and possessed a high limiting oxygen index (LOI) value of 32.5 %. GPIC coating would be covalently cross-linked onto silk fabric and the coated silk fabric could withstand 30 washing cycles, displaying high washing durability. GPIC coating also significantly suppressed the smoke and heat generation of silk fabric during combustion. The coated silk fabrics had high thermal stability and left significant inflated char residues after the burning tests. The intumescent FR performance of GPIC was beneficial from the synergistic effect of phytate and triazine-trione groups.

Synthesis of network polymers by means of ring-opening addition reaction of a tri-aziridine and dicarboxylic acid compounds

Polyethylenimine (PEI) is widely used in various products. Development of PEI network polymers would expand the application of the PEI. Ring-opening homo-polymerization of tri-aziridine compounds yielded the PEI-based hard network polymers derived from high dense crosslinking structure. Introduction of the flexible unit in the polymer network should be effective to control the mechanical properties of the resulting network polymers. In the present study, ring-opening addition reactions between a tri-aziridine, 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] (3AZ), and α,ω-dicarboxylic acid, RCAn (HOOC-(CH2)n-COOH): succinic acid (RCA2), adipic acid (RCA4), dodecanedioic acid (RCA10), or α,ω-dicarboxylic acid with ether linkage, ECAm (HOOC-(CH2OCH2)m-COOH); diglycolic acid (ECA1), 3,6,9-triocaundecanedionic acid (ECA3), poly(ethylene glycol) bis(carboxymethyl) ether (ECA4) were conducted to yield the polymers with controlled network structure. The reactions at room temperature in N,N-dimethylformamide successfully yielded gels. Young's modulus of the gel decreased with increasing in the chain length of the dicarboxylic acid used. The reaction of 3AZ with RCA4 in acetone or ethanol (EtOH) induced phase separation and produced porous polymers. The reactions with oxalic acid (RCA0), glutaric acid (RCA3), suberic acid (RCA6), ECA1, ECA3, or ECA4 in EtOH also yielded the porous polymers. The morphology in the porous polymers was formed by connected particles. The Young's modulus of the porous polymer also decreased with increasing in the chain length of the dicarboxylic acid used. The resulting porous polymers absorbed various solvents, such as acetone, water, dichloromethane, and chloroform. Hydrophobicity and hydrophilicity of the porous polymers can be controlled by the molecular structure of the dicarboxylic acid in the polymer networks.

Phosphorus Containing Rubber Seed oil as a Flame Retardant Plasticizer for Polyvinyl Chloride

The application of phthalate plasticizers has been restricted around the world due to their poor migration and potential harm to the human body. Hence, producing functional bio-based plasticizers via exploiting clean and reusable resources meets the satisfaction of current demands. In this study, flame-retardant rubber seed oil-based plasticize (FRP) was prepared via epoxidation reaction and ring opening addition reactions, which was used as a flame-resistant plasticizer for polyvinyl chloride to replace petroleum-based phthalate plasticizer. When DOP was replaced with FRP, the torque of PVC blends increased from 11.4 to 18.4 N⋅m, the LOI value increased from 24.3% for PVC-FRP-0% to 33.1% for PVC-FRP-20. The THR value diminished from 39 MJ/m2 (pertaining to PVC-FRC-0) to 22 MJ/m2 Tg increased from 23°C to 47°C, the weight loss of plasticized PVC blends significantly reduced from 22.6% to 2.8% in leaching tests. The study provided a new way to prepare flame retardant plasticizer using rubber seed oil as raw material.

Synthesis of network polymers by ring-opening addition reaction of multi-functional epoxy and dithiol compounds

Synthesis of network polymers by ring-opening addition reaction of multi-functional epoxy and dithiol compounds

Excellent UV-absorbing cotton fabric with high durability and hydrophobicity based on surface-initiated ATRP of polymerizable organic UV-absorber

Ultraviolet (UV) protective cotton fabric is a convenient and reliable way to protect human body from sunlight. Herein, a polymerizable UV-absorber, 2-hydroxy-4-(3-methacryloxy-2-hydroxylpropoxy) benzophenone (BPMA) was prepared from the ring-opening addition reaction of 2,4-dihydroxybenzophenone (UV-0) with glycidyl methacrylate. The initiators tethered cotton fabric (CF-Br) was prepared by the immobilization of α-bromoisobutyryl groups. PBPMA grafted cotton fabric (CF-g-PBPMA) was fabricated via surface-initiated activators generated by electron transfer for atom transfer radical polymerization (SI-AGET ATRP). The results indicated that the structure of targeted polymerizable BPMA was defined, and PBPMA chains were successfully grafted from CF-Br to obtain CF-g-PBPMA. Compared with the UV protection factor (UPF) of the original cotton fabric (3.5), the UPF of CF-g-PBPMA achieved 79,630.2 at PBPMA polymerization degree of 404 due to the incorporation of 2-hydroxy benzophenone in repeating units of PBPMA. The as-prepared CF-g-PBPMA can be labeled as "Excellent UV Protection" according to the ASTM D 6603 with UPF values of above 40. Compared with the original cotton fabric, the CF-g-PBPMA displayed excellent superhydrophobicity with the water contact angle (WCA) increasing from 46° to 154° due to the increased surface roughness of cotton fabric induced by the accumulated PBPMA. After 200 washing cycles, the chemically bonded PBPMA enabled the CF-g-PBPMA outstanding durability with the WCA and UPF achieving 135° and 730.5, respectively.Graphical abstract

Photoredox-Catalyzed Ring-Opening Addition Reaction between Benzyl Bromides and Cyclic Ethers

AbstractA novel nucleophilic reaction between cyclic ethers and benzyl bromides is achieved under photoredox catalysis. The reaction proceeds through a single-electron-transfer (SET) pathway rather than a common SN2 mechanism. By two steps of reduction and oxidation, a benzyl bromide heterolyzes to give a carbocation and bromide ion under mild conditions, and then a cyclic ether captures both the carbo­cation and bromide ion to afford the addition product.

Fe3O4@SiO2 nanoparticle-supported Co(III)-Salen composites as recyclable heterogeneous catalyst for the fixation of CO2

Magnetic nanoparticle-supported heterogeneous catalysts have been widely researched in green catalysis, due to their convenient magnetic separation and nanometer effects. Herein, a magnetic Co(III)-Salen heterogeneous catalyst with uniform spherical core-shell structure was synthesized for the chemical fixation of CO2 into cyclic carbonate based on the sustainable protocol development and green chemistry principles. Fe3O4@SiO2 nanoparticles with uniform spherical core-shell structure were prepared by the reverse microemulsion method, and Co(III)-Salen complexes were subsequently immobilized on the resulted Fe3O4@SiO2 nanoparticles via covalent bonding, leading to Fe3O4@SiO2@Co(III)-Salen nanocomposites with particle size of 29 nm and saturation magnetization value of 27.2 emu/g. The catalytic performance study indicated that the catalyst exhibited high yield of 99% with selectivity of 100% for the ring-opening addition reaction of CO2 and epoxide under solvent-free reaction condition. A plausible reaction mechanism was proposed that the Lewis acidic sites of Co(III)-Salen and nucleophilic bromine ion components played synergetic roles in promoting cycloaddition reactions. A stable geometry of the Co(III)-Salen complex and a detailed evidence for the reaction mechanism were provided by the density functional theory (DFT) calculations. Based on their excellent magnetic properties, the Co(III)-Salen nanocomposites could be easily recovered by using an external magnet and reused for 5 times without significant leaching of metal center and loss of catalytic activity.

Synthesis of a Novel Flame Retardant Containing Phosphorus, Nitrogen, and Silicon and Its Application in Epoxy Resin.

A novel flame retardant (TDA) containing phosphorus, nitrogen, and silicon was synthesized successfully via a controllable ring-opening addition reaction between 1,3,5-triglycidyl isocyanurate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 3-aminopropyltriethoxysilane, and TDA was then blended with diglycidyl ether of bisphenol A to prepare flame-retardant epoxy resins (EPs). The chemical structure and components of TDA were confirmed by Fourier transform infrared (FTIR) spectra, 31P nuclear magnetic resonance, and X-ray photoelectron spectroscopy. Thermogravimetric analysis results indicated that after the introduction of TDA, cured EP maintained good thermal stability with a minimum initial decomposition temperature of 337.6 °C, and the char yields of a EP/TDA-5 sample significantly increased by 76.2% compared with that of the neat EP thermoset. Additionally, with the addition of 25.0 wt % TDA (1.05 wt % phosphorus loading), the limited oxygen index value of cured EP increased from 22.5% of pure EP to 33.4%, and vertical burning V-0 rating was easily achieved. Meanwhile, after the incorporation of TDA, the total heat release and total smoke production of the EP/TDA-5 sample obviously reduced by 28.9 and 27.7% in the cone calorimeter test, respectively. Flame-retardant performances and flame-retardant mechanisms were further analyzed by scanning electron microscopy, FTIR, energy-dispersive spectrometry, and pyrolysis gas chromatography/mass spectrometry. The results reveal that the synergistic effect of phosphorus, nitrogen, and silicon plays an excellent flame-retardant role in both gaseous and condensed phases. In addition, the mechanical and dynamic mechanical properties of cured EP thermosets are well maintained rather than destroyed. All the results demonstrate that TDA endows epoxy resin with excellent flame retardancy and possesses great promise in the industrial field.

One-Pot Nonisocyanate Synthesis of Sequence-Controlled Poly(hydroxy urethane)s from a Bis(six-membered cyclic carbonate) and Two Different Diamines

Sequence-controlled synthetic polymers have received increasing interest because of their great potential to develop next-generation functional materials. Here, we report a facile synthesis of a symmetric spiro bis(six-membered cyclic carbonate), 2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-dione (1), its reactivity, and a one-pot, nonisocyanate synthesis of sequence-controlled poly(hydroxy urethane)s (PHUs) from 1 with two different symmetric diamines. The second-order rate constant for the ring-opening addition reaction of one of the two cyclic carbonates of 1 with 1-hexylamine is two orders of magnitude larger than that of the remaining one of the resulting intermediate due to a remarkable difference between their ring strain energies. This difference in the reactivity enables the selective formation of a diurethane-linked bis(six-membered cyclic carbonate) from the reaction of 1 with a diamine (0.5 equiv). The subsequent addition of a different diamine (0.5 equiv) to the same pot affords sequence-controlled PHUs with an ABAC sequence.

Endowing magnesium with the corrosion-resistance property through cross-linking polymerized inorganic sol-gel coating.

The design of a highly adhesive, defect-free and low-temperature sol–gel coating for the protection of magnesium alloys is desirable yet challenging. In this study, a novel SiO2-based sol–gel coating is developed by a ring-opening addition reaction. Notably, the integration of individual sol clusters endows the sol–gel coating with a smooth and compact surface morphology, and eliminates the potential corrosion site of the low-temperature-prepared sol–gel coating. Besides, the as-obtained sol–gel coating exhibits excellent metallic adhesion nature. Most importantly, it increases the overall impedance modulus by 27 times than that of the conventional strategy and decreases the corrosion rate from 3.8 ± 0.5 mg cm−2 per day (commercial chromate conversion coating) to 0.5 ± 0.2 mg cm−2 per day.

Synthesis of Network Polymers by Means of Addition Reactions of Multifunctional-Amine and Poly(ethylene glycol) Diglycidyl Ether or Diacrylate Compounds.

Addition reactions of multi-functional amine, polyethylene imine (PEI) or diethylenetriamine (DETA), and poly(ethylene glycol) diglycidyl ether (PEGDE) or poly(ethylene glycol) diacrylate (PEGDA), have been investigated to obtain network polymers in H2O, dimethyl sulfoxide (DMSO), and ethanol (EtOH). Ring opening addition reaction of the multi-functional amine and PEGDE in H2O at room temperature or in DMSO at 90 °C using triphenylphosphine as a catalyst yielded gels. Aza-Michael addition reaction of the multi-functional amine and PEGDA in DMSO or EtOH at room temperature also yielded corresponding gels. Compression test of the gels obtained with PEI showed higher Young’s modulus than those with DETA. The reactions of the multi-functional amine and low molecular weight PEGDA in EtOH under the specific conditions yielded porous polymers induced by phase separation during the network formation. The morphology of the porous polymers could be controlled by the reaction conditions, especially monomer concentration and feed ratio of the multi-functional amine to PEGDA of the reaction system. The porous structure was formed by connected spheres or a co-continuous monolithic structure. The porous polymers were unbreakable by compression, and their Young’s modulus increased with the increase in the monomer concentration of the reaction systems. The porous polymers absorbed various solvents derived from high affinity between the polyethylene glycol units in the network structure and the solvents.

Advanced Polymers from Simple Benzoxazines and Phenols by Ring-Opening Addition Reactions

Simple benzoxazines were mixed and reacted with various phenolics such as phenol, p-nitrophenol, p-cresol, 1,3-dihyroxybenzene (resorcinol), 1,3,5-trihydroxybenzene (phloroglucinol), and N-(2-hydro...

Preparation of low shrinkage stress dental composite with synthesized dimethacrylate oligomers

Two dimethacrylate oligomers named polypropylenglycol bis(2-hydroxy-3-methoxypropyl) dimethacrylates (380PPMA and 640PPMA) with different molecular weight were synthesized through ring opening addition reaction between epoxy terminated oligomers PPDE and methacrylic acid, and their structures were confirmed by FT-IR and 1H-NMR spectra. The PPMAs were used to replace TEGDMA partially in Bis-GMA/TEGDMA (50/50, wt./wt.) with the aim to reducing volumetric shrinkage and shrinkage stress of dental resin composites. Dental resin composite without PPMAs was used as control. Double bond conversion (DC), volumetric shrinkage (VS), shrinkage stress, water sorption (WS) and solubility (SL), flexural strength (FS) and modulus (FM) of experimental dental resin composites were investigated. Dynamic mechanical analysis (DMA) was used to evaluate the glass transition temperature (Tg), heterogeneity, and crosslink density (υ). The results showed that dental resin composites contained 640PPMA had slower polymerization rate. Only dental resin composites with 20 wt% of 640PPMA in resin matrix had lower VS than control group (p < 0.05). All of PPMAs containing composites had lower shrinkage stress than control group (p < 0.05). Before water immersion, all of experimental dental resin composites had the same FS and FM (p > 0.05), while after water immersion, FM of dental resin composites with PPMAs became lower than control (p < 0.05). Higher WS and SL were observed in composites with 640PPMA (p < 0.05). Incorporation of PPMAs into dental resin composites could decrease Tg and crosslink density (p < 0.05), but more homogeneous materials could be obtained (p < 0.05). Therefore, PPMAs could be used to reduce volumetric shrinkage and shrinkage stress of dental resin composites, but further studies concerned biocompatibility and service life should be taken because of the higher WS and SL.

Synthesis and Bacteriostatic Activities of Modified Flutriafol Derivatives

This study aimed to evaluate the preservative ability of modified flutriafol derivatives against decay fungi. The bacteriostatic effect of flutriafol on Trichoderma viride was not efficient as expected. Flutriafol was modified as a parent substrate to improve its broad spectrum performance. Six triazole compounds were synthesized by Friedel–Crafts reaction, oxygen–sulfur–ylide reaction, and ring-opening addition reaction. The structures of the target products were determined by 1H NMR and MS. Antibacterial and antileakage tests were performed to optimize the most efficient agents among triazole target products.

Thermoresponsive and acid-cleavable amphiphilic copolymer micelles for controlled drug delivery

ABSTRACTThermoresponsive and acid-cleavable amphiphilic block copolymers poly(N-isopropylacrylamide)-acetal-poly(4-substituted-ε-caprolactones) (PNiPAAm-a-PXCLs) containing an acidic-cleavable acetal linkage at the junction between the temperature-sensitive hydrophilic PNiPAAm and the degradable hydrophobic block PXCL were synthesized through ring-opening polymerization and electrophilic addition reactions. These polymer solutions showed reversible changes in optical properties and a lower critical solution temperature in the range of 32.0–46.4°C. The copolymers formed micelles in aqueous solution with critical micelle concentrations in the range of 0.83–15.95 mg L−1 had hydrodynamic sizes of <200 nm and were spherical. Under the combined stimulation of temperature and pH, the micellar nanoparticles could be dissociated; the loaded molecules could be released from the assemblies more efficiently than that under only one stimulus or without stimulus. In addition, the nanoparticles exhibited low toxicity against human cervical cancer (HeLa) cells at concentrations ≤1000 µg mL−1. Doxorubicin-loaded PNiPAAm11-a-PCL28 micelles also effectively inhibited the proliferation of HeLa cells with a half-maximal inhibitory concentration (IC50) of 1.60 µg mL−1.

Insight into the Mechanism of Reversible Ring-Opening of 1,3-Benzoxazine with Thiols.

The reversible ring-opening addition and fragmentation reaction of p-cresol-based N-phenylbenzoxazine with aliphatic and aromatic thiols was investigated in solvent-mediated and solvent-free reactions. Independently of the used thiol, N-phenylbenzoxazine and the thiols reacted to equilibrium with comparable amounts of reactants and products in aprotic solvent, whereas in protic solvent almost full conversions were reached. In contrast, thiol reactivity was a crucial factor in solvent-free reactions yielding fast and complete conversions for a more acidic thiol and balanced equilibrium concentrations in case of thiols with high pKa values. The strong influence of thiols with low pKa values emphasizes the relevance of the protonation step in the ring-opening reactions of 1,3-benzoxazines with thiols in absence of solvents where acidity predominates nucleophilicity. The reverse reactions, namely adduct dissociation and benzoxazine recovery, were successfully conducted at elevated temperatures and reduced pressure facilitated by the removal of the formed thiols yielding up to 95% recovered 1,3-benzoxazine. These results provide deeper understanding of the reversible ring-opening reaction mechanism of 1,3-benzoxazine with thiols.