Synthesis and characterization of amide linkage-incorporated polyethyleneimine-based chelating resins and studies of the crosslink density and surface properties on metal ion uptake

The chelating resins incorporating amide linkages were synthesized in open reaction vessels (OV) by polycondensing different proportions, viz., 1 : 1, 1 : 1.3, and 1.3 : 1 of polyethyleneimine (PEI) and diethylenetriaminepentaacetic acid (DTPA), respectively, at 145–155°C, and at varying curing times (15 h and 22 h). For the proportion 1 : 1, the synthesis was performed in a closed reaction vessel (CV) as well. The resins were characterized by FTIR, elemental, and thermogravimetric analysis, apart from sarptometric surface studies. The extent of crosslinking was evaluated by swelling measurements and the chemical stability was assessed by acid and alkali treatment. The effect of the mode of heating and curing times on the extent of crosslinking and pore structure modifications were evaluated. The influence of these factors on the capacities, the kinetics, and the break through curve trends of these resins were studied using zinc and cadmium metal ions as references. The reproducibility of the resins were ascertained by assessing the extent of change in the break through curve trends of their different batches, synthesized under identical conditions. © 1993 John Wiley & Sons, Inc.     

Fluorescence polarization and rheological studies of the poly(N-vinyl-2-pyrrolidone) hydrogels produced by UV radiation

Poly(N-vinyl-2-pyrrolidone) hydrogels produced by direct ultraviolet irradiation of PVP aqueous solution leads to crosslinking through pyrrolidinone moiety photolysis. Generally, hydrogel physical properties, like crosslinking density, pore size, swelling capacity, storage and loss moduli are obtained by swelling and rheological tests. However, relations between anisotropy obtained by fluorescence polarization studies and these properties have not been addressed for hydrogel systems. In this work we show that there is a correlation between the data obtained from anisotropy and rheological experiments, since both of them are related with crosslinking density of the hydrogels. These results reveal that fluorescence polarization spectroscopy is a promising tool for understanding the structure of hydrogels.     

Recovery of uranium from sea water. IV. Influence of crosslinking reagent of the uranium adsorption of macroreticular chelating resin containing amidoxime groups

Macroreticular chelating resins (RNH) containing amidoxime groups with various degrees of crosslinking were synthesized by using various amounts of ethyleneglycol dimethacrylate (1G), dimethyleneglycol dimethacrylate (2G), triethyleneglycol dimethacrylate (3G), tetraethyleneglycol dimethacrylate (4G), and nanoethyleneglycol dimethacrylate (9G) as crosslinking reagent. The effect of crosslinking reagents on the pore structure, ion exchange capacity, swelling ratio, and adsorption ability for uranium of RNH was investigated. RNH (RNH–1G) prepared by using 1G were showed to have macroreticular structures by the measure of specific surface area. RNH–1G had the high adsorption ability and physical stability. Though RNH (RNH–4G) obtained by using 4G have little macroreticular structure (macropore), these resins showed the high adsorption ability for uranium by the treatment with 0.1 mol dm^?3 NaOH at 30°C for 15 h (alkali treatment). These results suggest that the formation of not only the favorable macropore but also the micropore is important for the effective recovery of uranium in sea water, whereas RNH–4G was defined to be low physical and chemical stability. For the preparation of RNH which have effective pore structure for the recovery of uranium, chemical, and physical stability, the simultaneous use of divinylbenzene (DVB) and 1G or 4G as crosslinking reagent was examined (abbreviated as RNH–DVB–1G and RNH–DVB–4G). The specific surface area of RNH–DVB–1G increased with an increase of 1G used. These RNH–DVB–1G have been shown the high adsorption ability for uranium. On the other hand, the specific surface area and adsorption ability for uranium of RNH–DVB–4G decreased with an increase of 4G used. Repeated use did not cause the deterioration of both RNH–DVB–1G and RNH–DVB–4G. This result suggests that the simultaneous use of DVB and 1G or 4G contributed the improvement of chemical and physical stability. In particular, RNH–DVB–1G has the effective macropore and micropore for the recovery of uranium.     

Decomposable crosslinking paint

This study describes a novel paint technology that meets the recycling needs of industrial products. The decomposable crosslinking paint exhibits good properties throughout its use in the natural environment, and after use, it can be easily eliminated in a special process to recover the substrates. The paint was cured by a reaction between a carbonyl group of resins and a hydrazide group of crosslinking agents. The reverse reaction could be promoted by three essential components: water (reactive material), an acid (catalyst), and a solvent (diluent between active groups). The paint film was eliminated by dipping the paint in the solution containing these three components. The rates of dissolution were determined by water content, acid strength, swelling intensity of solvent, and dipping temperature. 17-1, Higashi Yawata 4-Chome, Hiratsuka-Shi, Kanagawa-Ken 254-8562, Japan.     

Solvolyse- und umesterungsreaktionen bei der vernetzung von alkyd- und acrylatharzen mit melaminvernetzern

One acrylic and different alkyd resins were cured with a melamin resin. Technical properties, swelling degrees, relativ IR-absorbances, and volatiles in the waste gas were determined quantitatively. From these data the amount of iso-butanol for the crosslinking and selfcondensation reactions can be calculated. In addition it was observed a solvolysis reaction of the alkyd resin and a transesterification reaction of the acrylic resin because of the reaction of the ester groups with the iso-butanol eliminated from melamine resin. Evidence is given for the solvolysis reaction by investigation of the specific cleavage products by means of IR, GPC, and GC/MS measurements. A pathway for the solvolysis reaction is proposed.     

Preparation and characterization of thermosensitive beads with macroporous structures

Thermosensitive copolymers of poly(N‐isopropyl acrylamide)‐co‐2‐hydroxyethyl methacrylate (NIPA‐co‐HEMA) macroporous resins were synthesized in the form of beads by inverse suspension polymerization. The copolymerization was carried out in aqueous solutions of the comonomers dispersed by cyclohexane with stabilizers. A series of resins with different molar ratios of NIPA : HEMA, and different crosslinking degrees was obtained. The compositions of the copolymers were determined by elemental analysis. The results showed that the content of HEMA in a copolymer was higher than that of the corresponding feed mixture from which the copolymer was made. IR spectra also confirmed the structure of the copolymers. The porous parameters such as true densities, apparent densities, pore volumes, and porosities of the resins were measured by means of pycnometry. The determination of equilibrium swelling ratios and measurement of differential scanning calibration indicated that the resins exhibited thermosensitivity in aqueous solutions. Finally, the loading of hydroxyl groups was determined by titration. The resins have potential applications as supports in solid‐phase synthesis after being functionalized. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1792–1797, 2004     

Autocrosslinked isoporous polystyrene resins

Preparation and general characteristic features of resins prepared by autocrosslinking of styrene-vinylbenzyl chloride copolymers are described. When the crosslinking degree is high enough the resins present a large surface area, and a very narrow distribution of small pores. However, the most striking feature of these products are their swelling ability in both solvents and non solvents of polystyrene.     

Photocrosslinked norbornene–thiol copolymers: Synthesis,mechanical properties,and cure studies

A number of norbornene-functionalized resins were prepared and their photoinitiated crosslinking reaction with a multifunctional thiol was studied. Access to these novel resins can be gained by several synthetic routes. The most general of these routes is the [4π + 2π] cycloaddition reaction (the Diels–Alder reaction) of the corresponding multifunctional acrylate ester with cyclopentadiene (CPD) monomer. The photocrosslinking reaction of these resins with multifunctional thiols such as pentaerythritol tetramercaptopropionate (PETMP) is quite rapid and sensitive to low UV dose as well as dose rate. FT-IR cure studies also indicated that the cure rate slows down dramatically as the conversion approaches the calculated gel points for the systems under study. Mechanical properties of cured thin films of these materials exhibited a wide range of tensile and dynamic mechanical properties, which depended on the structure of starting materials used in the preparation of the norbornene resin and the crosslinking thiol.     

Chelating resins for mercury extraction based on grafting of polyacrylamide chains onto styrene–divinylbenzene copolymers by gamma irradiation

Chelating resins for mercury adsorption were prepared by grafting polyacrylamide chains onto styrene–divinylbenzene (Sty–DVB) copolymers by applying gamma radiation. Sty–DVB copolymers were synthesized by aqueous suspension polymerization employing different synthesis conditions. The copolymers were characterized by apparent density, surface area, pore size distribution and swelling capacity. The copolymers were irradiated using a ⁶⁰Co-γ source at room temperature in the presence of acrylamide solution in methanol. The grafting reaction was evaluated with the aid of elemental analysis, FTIR and thermogravimetric analysis (TGA). Hg(II) uptake measurements were carried out in batch experiments. The results showed that these resins can be successfully used for Hg(II) adsorption at ppm levels. The porosity degree of the copolymers influences the grafting yield as well as the Hg(II) complexation capacity of the chelating resins.     

Zur kinetik der Vernetzung von Epoxidharzen

The crosslinking of epoxy resins,—phenylglycidylether as a model system as well as monomers and oligomers of diglycidylether of bisphenol A and of hydantoine resins—, with acid anhydride in presence of amine accelerators has been investigated. Experimental methods used were chemical analysis, dilatometry and calorimetry. From the determination of the chemical yield resulted, that crosslinking of epoxy and anhydride is a zero order reaction, but for longer distances of reaction time different rate constants must be used, leading to large differences in the activation energies of the steps of crosslinking. From time dependant deviations of the anhydride conversion yield from stochiometry it was concluded, that at first an intermediate compound originates and the linking of these units in the network determines the second step of crosslinking.     

Properties of elastomers crosslinked by bisglycidyl ether of 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane

Chlorobisphenolic epoxy resins in crystalline form, e.g., bisglycidyl ether of 2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (BGECBP) and the system sulfur–N-cyclohexyl-2-benzothiazolesulfonamide were used as crosslinking agents for vulcanization of butadiene–styrene and butadiene–acrylonitrile rubber. The density of crosslinking was determined by the equilibrium swelling method and on the basis of the Mooney-Rivlin equation which gives the relation between stress and elongation. The dynamic properties, namely, G′ and G″ and mechanical loss factor δ, were determined. On the basis of these results, mechanisms for the crosslinking reaction were advanced, the activation energy was determined, and comparisons between crosslinking rates by different systems were made. It was found that vulcanizates crosslinked by BGECBP possess higher heat aging resistance and lower glass transition temperatures in comparison with those crosslinked by means of sulfur in the presence of N-cyclohexyl-2-benzothiazolesulfonamide.     

Introduction of two polyvinyl alcohol resins for efficient solid support Cu-catalyzed N-arylation of α-aminoacids with aryl halides in aqueous media

In this article, two polyvinyl alcohol (PVA)-based resins were prepared by crosslinking of epoxidized PVA-chains using of 4-(4-aminobenzyl)benzenamine as a crosslinker and polymerization of acrylated PVA chains in the another approach. The prepared PVA resins showed well hydrophilic and swelling properties in various organic solvents, which are used in solid-phase organic synthesis (SPOS). Swelling properties of these resins were examined in dimethylformamide, tetrahydrofuran, water, ethanol, methanol, dichloromethane, and dioxane. Furthermore, the both resins were characterized by FTIR and ¹H-NMR and their properties such as epoxy equivalent weight (EEW) of epoxidized PVA and density of the resins were determined by analytical methods. Then, α-amino acids such as L-aspartic acid, L-leucine, L-alanine, L-serine, L-valine, L-threonine, and L-tyrosine were immobilized on both resins through esterification reaction between these α-amino acids with the present hydroxyl groups on PVA resines, to carry out their solid-phase N-arylation reaction in the presence of CuI as a catalyst in milder and greener conditions than free resin protocols. Hydrolysis of the correponding N-arylated α-amino acids immobilized on the resins gave the N-arylated α-amino acids in high to excellent yields. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47597.     

Structure-property relationships in PMR-type polyimide resins: 1. Novel anthraquinone-based PMR resins

Novel aromatic polyimides prepared via the polymerization of monomeric reactants (PMR) approach and incorporating anthraquinone diamines in the main chain have been characterized. Imidization and crosslinking reaction profiles have been delineated by d.m.t.a. and the high-temperature mechanical and thermal properties of the thermoset resins examined. Elevated glass transition temperatures (> 300°C) are apparent in some resins while impairment of mechanical integrity is not evident below 450°C. All resins show good thermal and thermo-oxidative stability.     

Characterization of rubber particle size distribution of high-impact polystyrene using low-angle laser light scattering

A new application of low-angle laser light scattering has led to a new instrument capable of characterizing the rubber particle size distribution of high-impact polystyrene (HIPS) containing particles as small as 0.1 μ. Rubber particle size distributions of several HIPS resins have been characterized, and the particle size ranking of resins using light scattering parallels the ranking of resins using photomicroscopy. Several solvents have been employed to suspend the HIPS rubber particles for the scattering determination. Swelling of the rubber phase has been found to be relatively insensitive to variations in rubber phase crosslinking when methyl ethyl ketone is used to suspend the rubber particles. Particle swelling in methyl ethyl ketone does not detract from the usefulness of the light scattering method for HIPS rubber particle size characterization.     

Postcrosslinking of macroporous styrene–divinylbenzene copolymers via pendant vinyl groups: Effect of the starting copolymers on the pore structure of the postcrosslinked products

In the presence of anhydrous ferric chloride as a Friedel–Crafts catalyst, the postcrosslinking reaction of macroporous styrene–divinylbenzene (St–DVB) copolymers synthesized under different conditions was carried out with 1,2‐dichloroethane as a solvent. Without an externally added crosslinking agent, the specific surface area and pore volume, for copolymers with different DVB isomers or different DVB contents after reaction, in most cases increased significantly, and the increase was found to be heavily dependent upon the amount of the pendant vinyl groups in the starting copolymers. These results further confirm the role of the pendant vinyl groups in creating new crosslinking bonds in addition to those created by a free‐radical crosslinking reaction in the starting copolymers, and an alkylation reaction of the vinyl groups with neighboring aromatic rings is believed to dominate the course of the postcrosslinking at a relatively high level of the vinyl group contents. The synthesis conditions, including the n‐heptane content in a mixed diluent and the amount of the diluent, under which the starting copolymers were synthesized, play an important role in the increase of the surface area and pore volume of the copolymers after postcrosslinking. The effect of these conditions is attributed mainly to the swelling ability of the starting copolymers thus obtained in the solvent used for reaction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1668–1677, 2002     

Physical characterization of suspension-crosslinked polystyrene particles and their sulphonated products: 1. Nonionic networks

Suspension-crosslinked particles of polystyrene have been prepared via a novel Friedel-Crafts reaction. Their structure and physical behaviour have been investigated using mercury porosimetry and swelling studies. The crosslinking agent used was 1,4-dichloromethyl-2,5-dimethyl benzene which exhibits limited polycondensation under the crosslinking reaction conditions. The degree of polymerization of the crosslinking agent between two crosslinks has been estimated for the crosslinked systems. The average size of the network structure has been estimated also with reference to potential g.p.c. applications.     

Recovery of uranium from seawater. XII. Preparation and characterization of lightly crosslinked highly porous chelating resins containing amidoxime groups

A number of lightly cross-linked poly(acrylonitrile-co-divinylbenzene) beads (RN-5) have been synthesized by suspension polymerization. The use of solvating diluents such as chloroform, dichloroethane, and tetrachloroethane resulted in copolymer beads having highly porous structures. The chelating resins containing amidoxime as a functional group (RNH-5) have been prepared by the reaction of copolymer beads with 3% hydroxylamine in methanol. A detailed analysis is made of the pore structure of lightly cross-linked copolymers of acrylonitrile–divinylbenzene and their amidoxime derivatives in the anhydrous state including pore-size distribution, specific surface area, and pore structure in the aqueous media by means of gel permeation chromatography (GPC). A set of experiments have been performed to ascertain the potential of the resins for the adsorption of uranium from seawater. Because of their modified pore structures, the chelating resins exhibited a marked adsorption rate for uranium in seawater as high as 23 μg of U/cm³ of resin/day without alkaline treatment.     

The determination of the pore structural parameters of isoporous resins by inverse GPC

The swollen pore structure of a series of microporous isoporous resins (7.4–140 Å) are investigated with inverse GPC, n-alkylbenzenes and linear polystyrenes being used as probe molecules. The results indicated that, with the lowering of crosslinking degree of isoporous resins, the average pore diameter increased and the pore distribution curve broadened. All pore volume distribution obeyed a log-normal distribution. Based on the linear regression method, the experimental data were fitted to a monotonously declining exponential function and a normal distribution function by a computer, and some important structural parameters such as average pore diameter, pore volume distribution, specific surface area, etc. were obtained. The specific surface area of swollen gels were found much greater than those in the dry state measured by N₂ adsorption.     

Reinforcement of pH‐responsive γ‐poly(glutamic acid)/chitosan hydrogel for orally administrable colon‐targeted drug delivery

Orally administrable hydrogel was prepared by crosslinking chitosan (CS) with γ‐poly(glutamic acid) (γ‐PGA) for an excellent pH‐responsive colon‐targeted drug delivery system. The stable crosslinked amide bond appeared in the shifted region of FTIR spectroscopy, and the tensile strength and elastic modulus were also reduced by crosslinking of CS and γ‐PGA. The surfaces of crosslinked hydrogel have a homogeneous pore array with pore size corresponding to the varied blending ratio. The swelling ratio was dramatically changed by increasing the pH from 3 to 6, and the responsiveness of swelling ratio to the reversible pH changes between 3 and 10 was reliable for 72 h. The drug diffusion rate was mainly dependent on the pH, and a water‐soluble tetrazolium (WST‐1) assay indicated that cytocompatibility of the hydrogel was in an acceptable range. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci. 2013     

Curing of unsaturated polyester resins: Effects of comonomer composition. II. High-temperature reactions

The effects of comonomer composition of the curing kinetics of unsaturated polyester (UP) resins at 100–120°C were investigated by differential scanning calorimetry (DSC) and infrared spectroscopy (IR) over the entire conversion range. One commercial UP resin, UP2821, with 6.82 unsaturated C?C bonds per polyester molecule, was used. For styrene/UP2821 reactions, experimental results of the initial and maximum reaction rates by DSC at 100–120°C revealed that the styrene content, as well as the reaction temperature, would affect the formation of microgel structures. As the initial molar ratio of styrene to polyester C?C bonds increased, the styrene swelling effect could enhance the intramicrogel crosslinking reactions, while the styrene dilution effect could diminish the intermicrogel crosslinking reactions. The competition between the two reactions would depend on the reaction temperatures. Finally, a microgel-based reaction mechanism was proposed for the high temperature reactions. © 1993 John Wiley & Sons, Inc.