Cross‐metathesis of biorenewable dioxalates and diols to film‐forming degradable polyoxalates

Starting from commonly available sugar derivatives, a single step protocol to access a small family of isohexide‐dioxalates ( 2a–c ) has been established. The synthetic competence of 2a–c has been demonstrated by subjecting them to condensation polymerization. Quite surprisingly, the proton NMR of poly(isomannide‐co‐hexane)oxalate revealed a 1:2 ratio between isomannide‐dioxalate ( 2a ) and 1,6‐hexanediol ( 3a ) in the polymer backbone. This intriguing reactivity was found to be an outcome of a cross metathesis reaction between 2a and 3a . The cross metathesis products 3a ”[2‐(2‐methoxyacetoxy)ethyl 2‐(2‐hydroxyethoxy)‐2‐(λ3‐oxydanylidene)acetate] and 2a ‘(3R,6R)‐6‐hydroxyhexahydrofuro[3,2‐b]‐furan‐3‐yl methyl oxalate were isolated in a control experiment. Based on direct and indirect evidence, and control experiments, an alternative polymerization mechanism is proposed. Polymerization conditions were optimized to obtain polyoxalates P1(2a‐3a)‐P9(2c‐3c) with molecular weights in the range of 14,000–68,000 g/mol, and narrow polydispersities. The identity of the polyoxalates was unambiguously established using 1‐2D NMR spectroscopy, MALDI‐ToF‐MS, and GPC measurements. The practical implication of these polymers is demonstrated by preparing transparent, mechanically robust films. The environmental footprint of the selected polyoxalates was investigated by subjecting them to solution and solid‐state degradation. The polyoxalates were found to be amenable to degradation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1584–1592     

Deep insights into the hydrolysis of N,N‐dialkylaminoethyl methacrylates in aqueous solution with 1H NMR spectroscopy

N,N‐dialkylaminoethyl methacrylate (DAEA) monomers are extensively used to prepare multi‐responsive polymers. However, these monomers face high risk of hydrolysis in their ester groups when being polymerized in water‐containing medias. Here, NMR spectroscopy was employed to continuously track the hydrolysis and solubility of four widely used DAEA monomers [CH₂CH₂R₁COO(CH₂)₂N(R₂)₂; R₁ = H or CH₃; R₂ = CH₃, CH₂CH₃ or CH(CH₃)₂] under typical polymerization conditions. With this technique, the hydrolysis reactivity and absolute hydrolysis amount of these monomers are separately examined, and then their kinetic correlations with solubility, molecular structure, pH, and temperature are established, so that the hydrolysis of DAEA monomers and even other esters with similar cyclic structure can be predicted. The present efforts are expected to provide a general understanding for the hydrolysis of all the DAEA monomers, benefitting to the optimization of polymerization toward well‐defined DAEA copolymers, as well as the design of smart soft matter for specific applications. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 914–923     

Polyethylene Glycol‐(N‐Methylimidazolium) Hydroxide‐Grafted γ‐Fe2O3@HAp: A Novel Nanomagnetic Recyclable Basic Phase‐Transfer Catalyst for the Synthesis of Tetrahydrobenzopyran Derivatives in Aqueous Media

Polyethylene glycol‐(N‐methylimidazolium) hydroxide‐grafted hydroxyapatite encapsulated γ‐Fe₂O₃ nanoparticles, γ‐Fe₂O₃@HAp@PEG(mim)OH, were prepared and characterized by FTIR, SEM, TEM, TGA, and EDAX. This nanocomposite was applied as a novel, green, nanomagnetic, and recyclable basic phase‐transfer catalyst for the synthesis of tetrahydrobenzopyrans in high yields via the three‐component reaction of aromatic aldehydes, malononitrile, and dimedone or 1,3‐cyclohexanedione in aqueous media at ambient temperature.     

Hierarchical fractal‐structured allophanate‐derived network formation in bulk polyurethane synthesis

Polyurethanes are among the most applied and researched polymers worldwide. Nevertheless, polyurethane synthesis is accompanied by a side‐reaction occurring between isocyanate groups and the secondary nitrogen of already formed urethane groups, leading to the formation of crosslinking allophanates. This inevitably requires the development of highly diagnostic direct analytical methods that can be performed in the solid state of the polymer. The present research focused on the direct investigation and diagnostic determination of the chemical structure formation in bulk polyurethane synthesis, using a combination of Fourier transform infrared and solid‐state ¹³C nuclear magnetic resonance analysis. Polyurethane syntheses were performed in bulk and designed as to obtain significantly strong diagnostic analytical measurements signals for the accurate identification of each of the investigated chemical structures. The present research results led to the conclusive analytical identification of allophanate formation during polyurethane synthesis. In addition, the occurrence of a new reaction mechanism was discovered in the present research. It was demonstrated in the present research that this newly described reaction occurs via the further reaction of the allophanate secondary nitrogen with an isocyanate group, the reaction creating a tertiary nitrogen and an additional reactive secondary nitrogen, and so on, in a consecutive step progression, leading to the formation of a 3‐dimensional hierarchical fractal‐like crosslinked polymeric structure. Solid‐state ¹³C nuclear magnetic resonance analysis results were highly consistent with the Fourier transform infrared results. The discovery of this newly described reaction can facilitate the optimization of industrial processes and potentially opens a new door to the development of a vast variety of biomedical and nanotechnology applications.     

PHB (poly‐β‐hydroxybutyrate) and its enzymatic degradation

Our daily life needs depend on plastics, as they are cheap and durable, so they become the most commonly used synthetic chemical products. But from an environmentalist's point of view, a major concern related to these plastics is their non‐biodegradable nature. Driven by growing demand to search for sustainable solutions to dispose off generating huge volume of synthetic plastic wastes, shifted the mind of researcher towards the use of biodegradable plastics which can be completely disposed‐off by microbial enzymatic degradation. These biodegradable plastics or “bioplastics” are also synthesized by microbes under certain stressed environmental conditions out of which poly(R‐3‐hydroxybutyrate) (PHB) is the most ubiquitous and best known representatives of polyhydroxyalkanoate family. The PHB is most intensively used for the innovative biomedical applications owing to suitable combination of biocompatibility, transport characteristics, and mechanical properties. These challenging aspects of PHB can be used for designing of novel medical devices, in tissue engineering, and for systematic sustained drug delivery. Lots of research reports on PHB degrading enzymes and their producing microorganisms including biochemical aspects are available but in scattered form. So this review highlighted all the relevant information of PHB and PHB‐degrading enzymes starting with basic classification, synthesis, mechanism, and applications that are environment friendly and are of public interest.     

Degradation performance of polyglutamic acid and its application of calcium supplement

Degradable biopolymers with functional groups play a crucial role in the biomedical field. In this case, the influences of temperature and pH values on the degradation performance of poly (γ‐glutamic acid) (γ‐PGA) were fully explored by gel permeation chromatography. Further, γ‐PGA‐Ca was prepared by using calcium chloride to react with the low molecular weight γ‐PGA and characterized by Fourier transform infrared, differential scanning calorimetry test, gel permeation chromatography, atomic absorption spectrophotometric, Ca²⁺ release in vivo, and cytotoxicity experiments. Furthermore, Caco‐2 cell model was constructed to study the mechanism of γ‐PGA‐Ca intestinal absorption. Results indicated that low pH value and high temperature are the suitable conditions for the degradation of γ‐PGA. It also suggested that γ‐PGA‐Ca can be used as calcium supplements due to its high rate of absorption.     

Fluorescence sensing of 2,4,6‐trinitrophenol based on hierarchical IRMOF‐3 nanosheets fabricated through a simple one‐pot reaction

Hierarchical IRMOF‐3 nanosheets were firstly fabricated by a simple reflux strategy and were then characterized through Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, transmission electron microscopy and X‐ray photoelectron spectroscopy. They revealed a high fluorescence quantum yield (13.2%) and showed excellent selectivity and sensitivity for 2,4,6‐trinitrophenol (TNP) over a concentration range of 1–29 μM in aqueous solution. This work demonstrates that the facile fabrication method for hierarchical IRMOF‐3 nanosheets with favorable selectivity and sensitivity for TNP could produce a new point of view on novel metal–organic framework nanomaterials for on‐line detection of organic pollutants in water.     

HPLC–MS/MS analysis of peramivir in rat plasma: Elimination of matrix effect using the phospholipid‐removal solid‐phase extraction method

A simple HPLC–MS/MS method has been developed for the determination of peramivir in rat plasma in the present study. The analytes were separated on a C₁₈ column (50 × 2.1 mm, 1.7 μm) and a triple‐quadrupole mass spectrometer equipped with an electrospray ionization source was applied for the detection. A phospholipid‐free cartridge solid‐phase extraction was used to pretreat the plasma and eliminate the endogenous phospholipid. The in‐source collision‐induced dissociation approach showed that this pretreatment could result in negligible ion suppression from the extracted sample and could produce cleaner samples when compared with the protein precipitation. The method was linear over the concentration range of 0.12–1200.0 ng/mL for peramivir. The method was validated and successfully applied to a pharmacokinetic study after peramivir was orally and intravenously administered to Sprague–Dawley rats.     

Simultaneous determination of residues of metalaxyl,cyazofamid and a cyazofamid metabolite in tobacco leaves and soil by liquid chromatography with tandem mass spectrometry

A simple method was developed and validated for the simultaneous determination of metalaxyl, cyazofamid and the cyazofamid metabolite 4‐chloro‐5‐p‐tolylimidazole‐2‐carbonitrile (CCIM) by liquid chromatography with tandem mass spectrometry. The three target compounds were extracted from tobacco and soil with acetonitrile containing 0.1% acetic acid, and the extracts were purified using octadecylsilane. The proposed method showed satisfactory linearity (R² ≥ 0.9985) for the target compounds. The limits of detection for metalaxyl, cyazofamid and CCIM were 0.006, 0.06 and 0.06 mg/kg in soil and green tobacco leaves and 0.03, 0.3 and 0.3 mg/kg in cured tobacco leaves, respectively. The limits of quantification for metalaxyl, cyazofamid and CCIM were 0.02, 0.2 and 0.2 mg/kg in soil and green tobacco leaves and 0.1, 1 and 1 mg/kg in cured tobacco leaves, respectively. The average recoveries from soil and tobacco were 72.91–98.40% for metalaxyl, 76.73–105.80% for cyazofamid and 74.48–106.45% for CCIM. The relative standard deviation range was 1.23–6.99%. The developed method was successfully applied to analysis of residues of metalaxyl, cyazofamid and CCIM in real soil and tobacco samples. The results indicated that the established method could meet the requirement for the analysis of trace amounts of all three analytes in soil and tobacco.     

Determination of cycloserine in microdialysis samples using liquid chromatography–tandem mass spectrometry with benzoyl chloride derivatization

A new method for the analysis of cycloserine (4‐amino‐3‐isoxazolidinone, CYC) in rat microdialysis samples has been developed. This method consists of derivatizing the CYC with benzoyl chloride, which transforms primary amines into highly stable derivatives. An attractive feature of this method was that the derivatization reaction is straightforward and can be completed within 10 min. The formed derivative, in contrast to the non‐derivatized analyte, exhibited increased chromatographic retention and decreased matrix effects resulting from the co‐elution of other components using reversed‐phase liquid chromatography and on‐line switching. Detection on a quadrupole–linear ion trap mass spectrometer (AB3200 Q‐Trap) was performed using electrospray tandem mass spectrometry in multiple reaction monitoring mode. Various derivatization parameters were optimized in order to improve chromatographic separation and minimize ion suppression. In particular, the benzoylation reaction was improved to enhance the reproducibility and sensitivity of the chromatographic method. The transition m/z 207.1 → 105.1 was acquired to monitor the CYC derivatization products. The method was fully validated for its sensitivity, selectivity, matrix effect and stability. A good linearity over the selected range (r > 0.99, range = 22–2200 mg/L), as well as accuracy and precision within ±7% of the target values, was obtained. The assay described herein was successfully applied to quantitatively measure CYC in the lung and blood of anesthetized rats.