Synthesis,characterization, reactivity ratios by nuclear magnetic resonance spectroscopy,and application of (2,5‐Dichlorophenyl acrylate‐co‐glycidyl methacrylate) polymers as adhesives for the leather industry

2,5‐ Dichlorophenyl acrylate (DPA)‐co‐glycidyl methacrylate (GMA) polymers having five different compositions were synthesized in 1,4‐dioxane using benzoyl peroxide as a free‐radical initiator at 70 ± 0.5°C. Using ¹H‐NMR spectroscopy, the composition of the two monomers in the copolymers was calculated by comparing the integral values of the aromatic and aliphatic proton peaks. The reactivity ratios were calculated by Fineman–Ross (r₁ = 0.31 and r₂ = 1.08), Kelen–Tudos (r₁ = 0.40 and r₂ = 1.15), and extended Kelen–Tudos (r₁ = 0.39 and r₂ = 1.16) methods. The nonlinear error‐in‐variables model was used to compare the reactivity ratios. The copolymers were characterized by ¹H and proton decoupled ¹³C‐NMR spectroscopes. Gel permeation chromatography was performed for estimating the M_w and M_n and M_w/M_n of the poly(DPA) and copolymers (DPA‐co‐GMA: 09 : 91 and 50 : 50). Thermal stability of the homo‐ and copolymers was estimated using TGA [poly(DPA) > DPA‐co‐GMA (50 : 50) > DPA‐co‐GMA (09:91)], while DSC was utilized for determining the glass transition temperature. T_g increased with increased DPA content in the copolymer. The 50 : 50 mol % copolymer was chosen for curing with diethanolamine in chloroform. The cured resins were tested for the adhesive properties on leather at different temperatures (50, 90, 100, and 110°C). The resin cured at 50 °C exhibited a maximum peel strength of 1.6 N/mm, revealing a good adhesive behavior. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1167–1174, 2006     

STD‐NMR‐Based Protein Engineering of the Unique Arylpropionate‐Racemase AMDase G74C

Structure‐guided protein engineering achieved a variant of the unique racemase AMDase G74C, with 40‐fold increased activity in the racemisation of several arylaliphatic carboxylic acids. Substrate binding during catalysis was investigated by saturation‐transfer‐difference NMR (STD‐NMR) spectroscopy. All atoms of the substrate showed interactions with the enzyme. STD‐NMR measurements revealed distinct nuclear Overhauser effects in experiments with and without molecular conversion. The spectroscopic analysis led to the identification of several amino acid residues whose substitutions increased the activity of G74C. Single amino acid exchanges increased the activity moderately; structure‐guided saturation mutagenesis yielded a quadruple mutant with a 40 times higher reaction rate. This study presents STD‐NMR as versatile tool for the analysis of enzyme–substrate interactions in catalytically competent systems and for the guidance of protein engineering.     

On‐line LC‐NMR‐MS characterization of sesame oil extracts and assessment of their antioxidant activity

Sesame lignans were isolated by solvent extraction and subsequently purified by solvent crystallization from crude, unroasted sesame oil, and a sesame oil deodorizer distillate. In addition, an aliquot of the purified sesame oil extract was treated with camphorsulfonic acid to obtain a sesaminol‐enriched extract. The sesame lignan composition of the extracts was characterized by on‐line liquid chromatography nuclear magnetic resonance spectroscopy mass spectrometry coupling (LC‐NMR‐MS). The effect of the sesame oil extracts as well as pure sesame lignans and γ‐tocopherol on the oxidative stability of sunflower oil (lignan‐free) was studied by the Rancimat assay. The Rancimat assay revealed the following oxidative stability order: sesame oil extract < sesame oil deodorizer distillate < sunflower oil (no added sesame oil extracts) < sesamol < sesaminol‐enriched sesame oil extract. In addition, the radical‐scavenging capacity of these extracts was assessed by the Trolox® equivalent antioxidant capacity (TEAC) assay. The TEAC assay revealed a slightly different AOX activity order: sesamin < sesame oil extract < sesaminol‐enriched sesame oil extract < sesamol. In conclusion, the sesaminol‐enriched extract revealed strong antioxidant activity and is therefore suitable to increase the oxidative stability of edible oils high in polyunsaturated fatty acids.     

Konstruktion und Test eines Gradientensystems für NMR‐Diffusionsuntersuchungen in Grenzflächensystemen

A z‐gradient system for NMR diffusion measurements with intensive pulsed field gradients was redesigned. The gradient field of an actively screened gradient coil was optimized using finite element analysis. The gradient system was constructed with glass ceramic as coil support material. It does not show any background ¹H NMR signal and has a high current‐to‐gradient conversion factor of 0.37 T m^–1A^–1. The functionality of the system for studying slow diffusion processes in interface systems is demonstrated by observing isotropic and anisotropic diffusion in aqueous solutions of a PEO‐PPO‐PEO triblock copolymer and of methane in two different microporous crystalline absorbencies.     

Optimization of biodegradable PEG/PLGA nanofiber mats electrospinning process for anti‐adhesion application

Electrospinning is a direct, continuous, and useful technique to prepare nanofiber by applying electrostatic forces. In this study, poly(lactic‐co‐glycolic acid)/poly(ethylene glycol) (PLGA/PEG) nanofiber mats were prepared, and electrospinning process was optimized to obtain appropriate fiber diameter and hydrophilicity for anti‐adhesion application. Optimization of applied voltage, PEG content, and feeding rate was investigated using response surface methodology. A total of 15 trials were designed to optimize the parameters. Fiber diameter was measured using scanning electron microscopy. Individual and interactive effects of the solution properties were determined. Moreover, the adequacy of the models was verified by validation experiments. For anti‐adhesion test, a nanofiber mat was produced based on the suggested optimum electrospinning conditions. Results showed that optimum fiber diameters were obtained using 7.5% PEG content, applied voltage of 19 kV, and flow rate of 3 mL/h. Experimental results were in good agreement with the predicted fiber diameters. Furthermore, a rat model of sidewall defect‐cecum abrasion was employed to investigate the efficacy of PEG/PLGA in preventing postoperative peritoneal adhesions. Hence, this study provides an overview on the fabrication of PLGA/PEG nanofibers with targeted diameter, which may be used in anti‐adhesion. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46282.     

Counterion‐Switched Reversibly Hydrophilic and Hydrophobic TiO2‐Incorporated Layer‐By‐Layer Self‐Assembled Membrane for Nanofiltration

The manipulation of surface wettability has been regarded as an efficient strategy to improve the membrane performances. Herein, the counterion‐switched reversibly hydrophilic and hydrophobic surface of TiO₂‐loaded polyelectrolyte membrane are prepared by layer‐by‐layer assembly of poly(sodium 4‐styrene sulfonate) (PSS) and poly(diallydimethyl‐ammoniumchloride (PDDA) containing TiO₂@PDDA nanoparticles (NPs) on the hydrolyzed polyacrylonitrile (PAN) substrate membrane. The obtained polyelectrolyte multilayer (PEM) membranes [PEM‐TiO₂]_4.5⁺X^? (X^? = Cl^?, PFO^? [perfluorooctanoate] etc.) show different hydrophilicity and hydrophobicity with various counterions. The integration of TiO₂ NPs obviously improves the wettability and nanofiltration (NF) performance of PEM membrane for (non)aqueous system of dyes (crystal violet, eriochrome black T) with a high recyclability. The highly hydrophilic [PEM‐TiO₂]_4.5⁺Cl^? (water contact angle [WCA]: 13.2 ± 1.8°) and hydrophobic [PEM‐TiO₂]_4.5⁺PFO^? (WCA: 115.4 ± 2.3°) can be reversibly switched via counterion exchange between Cl^? and PFO^?, verifying the surface with a reversible hydrophilic–hydrophobic transformation. For such membranes, the morphology, wettability, and NF performance rely on the loading of TiO₂@PDDA NPs and surface counterion. Meanwhile, the motion and interaction of water or ethanol in the hydrophilic or hydrophobic membrane are revealed by low‐field nuclear magnetic resonance. This work provides a facile and rapid approach to fabricate smart and tunable wetting surface for potential utilization in (non)aqueous NF separation.     

Synthesis and performance measurement of environment‐friendly solidified dust suppressant for open pit coalmine

In this work, a new type of environment‐friendly solidified dust suppressant was developed to solve the dust pollution problem in open pit coalmines, coal bunkers, and so on. Natural polymer chitosan with excellent properties was chemically modified. Infrared spectroscopy was adopted to characterize the product. Using substitution rate as the evaluating indicator, the optimized mass ratio between monomer 3‐chloro‐2‐hydroxypropyl trimethyl ammonium chloride and chitosan, reaction temperature, reaction time, and pH were determined via single factor experiments. Combining the results of the four‐factor‐four‐level orthogonal experiment, the optimum reaction conditions A₂B₃C₄D₃ were obtained. The hardened film on the surface of coal powders was observed by high‐resolution scanning electron microscope. In addition, the water retention, solidification performance, and wind erosion resistance of the dust suppressant, as well as its influence on coal properties were measured. The results show that the synthesized dust suppressant demonstrates excellent properties and has good dust suppression effect. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46505.     

A Practical NMR‐Based High‐Throughput Assay for Screening Enantioselective Catalysts and Biocatalysts

Two NMR‐based approaches for high‐throughput screening of enantioselective catalysts and biocatalysts are described. One version makes use of pseudo‐enantiomers or pseudo‐meso‐compounds based on ¹³C‐labeling. A throughput of at least 1400 ee determinations per day is possible by using an appropriate flow‐through cell and an autosampler. The other approach is based on traditional diastereomer formation using a chiral reagent or complexing agent. The ee values are accurate to within ±2% and ±5% of the true values.     

Melamine‐bridged alkyl resorcinol modified urea–formaldehyde resin for bonding hardwood plywood

A powdery product was obtained by the reaction of methylolated melamine with alkyl resorcinols to form melamine‐bridged alkyl resorcinols (MARs). The effects of the addition of this powder on the bonding strength and formaldehyde emission of urea–formaldehyde (UF) resins were investigated. Three types of UF resins with a formaldehyde/urea molar ratio of 1.3 synthesized by condensation at pH 1.0 (UF‐1.0), pH 4.5 (UF‐4.5), and pH 5.0 (UF‐5.0) were fabricated. The addition of MAR to UF‐4.5 and UF‐5.0 for bonding hardwood plywood enhanced the bonding strength and reduced formaldehyde emission. For UF‐1.0, the addition of MAR adversely affected the bonding strength. However, the UF‐1.0 resin yielded the lowest formaldehyde emission of all of the UF resins in the study. The effects of the MAR addition were related to the molecular structures of the UF resins. UF‐1.0 contained a large amount of free urea, a considerable number of urons, and a highly methylene‐linked, ring‐structured higher molecular weight fraction and had a smaller number of methylol groups. Therefore, the addition of MAR was considered to cause a shortage of the methylol groups, which in turn, led to incomplete resin curing. In contrast to UF‐1.0, UF‐5.0 contained a smaller amount of free urea and a linearly structured higher molecular weight fraction and had a larger number of methylol groups. In this case, MAR was considered to effectively react with the methylol groups to develop a three‐dimensional crosslinked polymer network to enhance the bonding strength and suppress the generation of free formaldehyde to reduce formaldehyde emission. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparative 13C‐NMR and matrix‐assisted laser desorption/ionization time‐of‐flight analyses of species variation and structure maintenance during melamine–urea–formaldehyde resin preparation

The preparation of an industrially used sequential formulation of a melamine–urea–formaldehyde resin was followed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and ¹³C‐NMR analysis. The analysis allowed us to identify and follow the appearance, increase, decrease, and disappearance of a multitude of chemical species during the preparation of both the initial urea–formaldehyde (UF) phase of the reaction and the subsequent reaction of melamine with the UF resin that formed. The analysis indicated that (1) the increase and decrease in the species that formed proceeded through a cycle of the formation and degradation of species occurring continuously through what appeared to be a series of complex equilibria, (2) even at the end of the reaction a predominant proportion of methylene ether bridges was still present, (3) some small proportion of methylene bridges already had formed in the UF reaction phase of the resin even under rather alkaline conditions, and (4) the addition of melamine to the UF prepolymer induced some noticeable rearrangement of methylene ether bridges to methylene bridges. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Plasma‐modified poly(vinyl alcohol) membranes for the dehydrationof ethanol

Non‐porous poly(vinyl alcohol) (PVA) membranes prepared by a cast‐evaporating technique were covered with an allyl alcohol or acrylic acid plasma‐polymerized layer. The wettability and the surface energy, as well as the chemical nature of the deposit, were assigned by X‐ray photoelectron spectroscopy (XPS) and Fourier‐transform infrared spectroscopy (FTIR). The ability of the modified membranes for dehydrating the water/ethanol azeotropic mixture by pervaporation was studied at 25, 40 and 60 °C. The best selectivity (α = 250 at 25 °C) was obtained in the case of the allyl alcohol plasma treatment. The results obtained are discussed on the basis of the hydrophilicity as well as in terms of the weakly crosslinked superficial layer that favoured the membrane swelling. Copyright © 2003 Society of Chemical Industry     

Conformational Analysis of a High‐Mannose‐Type Oligosaccharide Displaying Glucosyl Determinant Recognised by Molecular Chaperones Using NMR‐Validated Molecular Dynamics Simulation

Exploration of the conformational spaces of flexible oligosaccharides is essential to gain deeper insights into their functional mechanisms. Here we characterised dynamic conformation of a high‐mannose‐type dodecasaccharide with a terminal glucose residue, a critical determinant recognised by molecular chaperones. The dodecasaccharide was prepared by our developed chemoenzymatic technique, which uses ¹³C labelling and lanthanide tagging to detect conformation‐dependent paramagnetic effects by NMR spectroscopy. The NMR‐validated molecular dynamics simulation produced the dynamic conformational ensemble of the dodecasaccharide. This determined its spatial distribution as well as the glycosidic linkage conformation of the terminal glucose determinant. Moreover, comparison of our results with previously reported crystallographic data indicates that the chaperone binding to its target oligosaccharides involves an induced‐fit mechanism.     

On non‐combustibility of commercial building materials

Non‐combustibility is discussed on the basis of experimental data for 66 commercial building materials obtained from two standard test methods: EN ISO 1716 oxygen bomb calorimeter and EN ISO 1182 cylindrical furnace. The sample materials are divided into five categories: concrete and ceramics, thermal/acoustic insulation materials, wall or ceiling boards, mortars and adhesives and thin coatings. To better distinguish between non‐combustible and combustible materials, an effective modified heat of combustion is defined and calculated for all materials tested in both methods. The materials studied exhibited very different mass loss values and a low tendency to auto‐ignite in the cylindrical furnace. Revised criteria for class A1 are proposed for better accuracy of reaction‐to‐fire assessment. It is proposed to use the oxygen bomb calorimeter with only one limit for the heat of combustion, that is, a value of 5 MJ/kg for all materials. The proposed approach is a very efficient tool for fast and inexpensive screening for non‐combustibility of building products and is expected to be a more precise method to distinguish between non‐combustible and combustible materials. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of polymer microstructure on the performance of post‐treated latex‐based pressure sensitive adhesives

Latex‐based butyl acrylate (BA)/acrylic acid (AA)/2‐hydroxyethyl methacrylate (HEMA) pressure sensitive adhesive (PSA) films with various microstructures were heated to improve their performance. The treated PSA films showed significantly better performance than original latex‐based PSA films with similar polymer microstructures. The effect of the heat treatment depended on the polymer microstructure of the untreated PSA films (or corresponding latices). Decreasing the amount of very small sol polymers (i.e., M_x < 2M_e) in gel‐free untreated PSA films, or both very small (i.e., M_x < 2M_e) and very large sol polymers (i.e., M_x > 20M_e) in gel‐containing untreated PSA films led to treated PSA films with significantly better performance. (Note: M_e is the molecular weight between two adjacent entanglement points in a polymer material.) In addition, simultaneously increasing the sol polymer molecular weight (M_w) as well as the size of the chain segments between two adjacent cross‐linking points (M_c) of the gel polymer in the original PSAs resulted in treated PSA films with better performance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012