Customized PEG-derived copolymers for tissue-engineering applications

PEG-containing copolymers play a prominent role as biomaterials for different applications ranging from drug delivery to tissue engineering. These custom-designed materials offer enormous possibilities to change the overall characteristics of biomaterials by improving their biocompatibility and solubility, as well as their ability to crystallize in polymer blends and to resist protein adsorption. This article demonstrates various principles of PEG-based material design that are applied to fine tune the properties of biomaterials for different tissue engineering applications. More specifically, strategies are described to develop PEG copolymers with various block compositions and specific bulk properties, including low melting points and improved surface hydrophilicity. Highly hydrated polymer gel networks for promoting cellular growth or suppressing protein adsorption and cell adhesion are introduced. By incorporating selectively cleavable cross-links, these hydrophilic polymers can also serve as smart hydrogel scaffolds, mimicking the natural extracellular matrix for cell cultivation and tissue growth. Ultimately, these developments lead to the creation of biomimetic materials to immobilize bioactive compounds, allowing precise control of cellular adhesion and tissue growth. [image: see text]     

New benzimidazole-2-yl-substituted polybenzimidazoles: Synthesis, properties, and hydrodynamic characteristics

The synthesis of novel benzimidazole-2-yl-substited polybenzimidazoles and initial compounds has been described. The polymers are studied by FTIR spectroscopy, TGA, and TMA. The hydrodynamic properties of macromolecules are investigated by translational diffusion and viscometry in 96% H₂SO₄; the molecular characteristics of the polymers are determined. Positive temperature dependences for intrinsic viscosities of the polymers are obtained. The polymers under study possess high hydrolytic stability with respect to sulfuric acid solutions up to 150°C and high thermal stability in the bulk. The TGA data correlate with the chemical structure of the polymers. The new polybenzimidazoles may be used as materials for the production of medium-temperature proton-conducting membranes.     

Synthesis and investigation of polybenzimidazoles containing alkyl substituents in aromatic nuclei

Polybenzimidazoles have been synthesized from 3,3′-diamino-5,5′-dimethylbenzidine, 3,3′,4,4′-tetraamino-5,5′-dimethyldiphenylmethane, bis(3-amino-4-methylamino)phenylmethane, bis(3-amino-4-methylamino-5-methyl)phenylmethane, and diphenyl esters of adipic, sebacic, isophthalic, and terephthalic acids and 4,4′-dicarboxydiphenyl oxide by solid-phase polyheterocyclization. Properties of the polybenzimidazoles have been studied. The polymers have high thermal stability. They are soluble in a number of organic solvents and give strong, elastic films. Solubility and thermal stability of polybenzimidazoles is determined by the methyl group position in the polymeric chain. The influence of other alkyl substituents on properties of polybenzimidazoles have been investigated. The polymer structure has been studied by infrared and PMR spectroscopy and elemental analysis.     

Tunable cross-linked copolymer networks for improvement of physical performance

The ability to tune the physical properties of polymeric materials through the different compositions in copolymer networks is suitable for the strategy of materials accompanied by combined high mechanical strength and stretchability simultaneously. Here, we developed a practical and straightforward strategy of a copolymer network structure via controlling the compositions of the acrylic-based urethane copolymers of diurethane acrylate (DUA) and diurethane cyclic acrylate (DUCA) with hydrogen-bonds through photo-polymerization. The copolymer networks led to the development of a physically cross-linked structure between the amide groups of DUA and/or DUCA and the hydroxyl groups of pentaerythritol ethoxylate (PEEL) by hydrogen-bonds. Based on the rheological analysis, the composition of the copolymer networks had a significant effect on the control of physical properties and development of cross-linked structure and thus led to the tunable comprehensive properties including high elastic modulus, high chain mobility and high recovery performance with a higher proportion of DUCA in the copolymer networks. Consequently, the tunable copolymer networks based on the developed physically cross-linked structure can improve the elastic properties, recovery performance, and healing ability simultaneously, providing significant progress in the fields of coating and adhesive.     

Equilibrium parameters of a liquid—vapor system and thermodynamic characteristics of adsorption of cyclic and cage hydrocarbons in squalane

The thermodynamic characteristics of adsorption of adamantane molecules and its alkyl derivatives, as well as some mono- and bicyclic hydrocarbons C₁₀H _n , were studied by equilibrium gas liquid chromatography on a column packed with the stationary liquid phase squalane under the conditions of infinitely low concentrations of the sorbate in the gas phase. The influence of specific features of the molecular structure of sorbates on the regularities of their retention on the column with squalane was shown. For the first time we obtained the limiting activity coefficients and excess thermodynamic functions of mixing, which made it possible to study in detail the thermodynamics of dissolution of cage molecules in the nonpolar liquid bulk. The changes in the molar isobaric heat capacity of sorbates during adsorption were determined by the chromatographic method. For reference compounds, these values agree well with the results of direct calorimetric measurements of the change in the molar standard isobaric heat capacity during vaporization.     

树脂对化工废水中有毒有机化合物的吸附作用机理与技术研究

超高交联吸附树脂对多种芳香有机化合物较高的吸附容量主要源于其密集的微孔和双峰孔分布.对大孔吸附树脂及超高交联吸附树脂采用不同极性功能基团进行化学修饰可以制得系列离子交换与吸附双重功能吸附树脂,该类树脂对亲水性有机污染物同时具有疏水、静电、络合等多重作用.丙烯酸酯类吸附树脂在吸附芳香磺酸盐时,树脂的骨架和功能基团对吸附过程都有重要的贡献.     

Adsorption of volatile organic compounds onto carbon nanotubes, carbon nanofibers, and high-surface-area graphites

The adsorption of different alkanes (linear and cyclic), aromatics, and chlorohydrocarbons onto different nonmicroporous carbons--multiwalled carbon nanotubes (CNTs), carbon nanofibers (CNFs), and high-surface-area graphites (HSAGs)--is studied in this work by inverse gas chromatography (IGC). Capacity of adsorption was derived from the isotherms of adsorption, whereas thermodynamic properties (enthalpy of adsorption, surface free energy characteristics) have been determined from chromatographic retention data. HSAGs present the highest adsorption capacity, followed by CNTs and CNFs (although CNTs present an intermediate surface area between the two HSAG studied). Among the different adsorbates tested, benzene exhibits the highest adsorption capacity, and the same trend is observed in the enthalpy of adsorption. From surface free energy data, enthalpies of adsorption of polar compounds were divided into dispersive and specific contributions. The interactions of cyclic (benzene and cyclohexane) and chlorinated compounds (trichloroethylene, tetrachloroethylene, and chloroform) with the surfaces are mainly dispersive over all the carbons tested, CNTs being the material with the highest dispersive contribution, as was deduced also from the entropy parameter. Adsorption parameters were correlated with morphological and chemical properties of the materials.     

Effect of carbon nanofiber functionalization on the adsorption properties of volatile organic compounds

The effect of the chemical activation, using HNO3, of a commercial carbon nanofiber (CNF) on its surface chemistry and adsorption properties is studied in this work. The adsorption of different alkanes (linear and cyclic), aromatic compounds and chlorohydrocarbons on both the parent and the oxidized CNF were compared. Temperature-programmed desorption results, in agreement with X-ray photoelectron spectroscopy experiments, reveal the existence of oxygen groups on the surface of the treated CNF. Capacity of adsorption was derived from the adsorption isotherms, whereas thermodynamic properties (enthalpy of adsorption, surface free energy characteristics) have been determined from chromatographic retention data. Both the capacity and the strength of adsorption decrease after the oxidant treatment of the carbon nanofibers, although in the case of chlorinated compounds the specific component of the surface energy shows an important increase. For n-alkanes and cyclic compounds, it was demonstrated that the presence of oxygen surface groups does not affect their interaction, the morphology of the surface being the key parameter. The oxidation of the nanofiber leads to steric limitations of the adsorption. In the adsorption of aromatic compounds, these limitations are compensated by the nucleophilic interactions between the aromatic ring and surface oxygenated groups, leading to similar performances of both materials. The absence of nucleophilic groups in the chlorinated compounds hinders their adsorption on the activated nanofibers.     

Supramolecular polymeric hydrogels

The supramolecular crosslinking of polymer chains in water by specific, directional and dynamic non-covalent interactions has led to the development of novel supramolecular polymeric hydrogels. These aqueous polymeric networks constitute an interesting class of soft materials exhibiting attractive properties such as stimuli-responsiveness and self-healing arising from their dynamic behaviour and that are crucial for a wide variety of emerging applications. We present here a critical review summarising the formation of dynamic polymeric networks through specific non-covalent interactions, with a particular emphasis on those systems based on host-guest complex formation, as well as the characterisation of their physical characteristics. Aqueous supramolecular chemistry has unlocked a versatile toolbox for the design and fine-tuning of the material properties of these hydrogels (264 references).     

Functionalization of crosslinked poly(4-vinylpyridine) and poly(4-vinylpyridine-co-styrene) with permanganate species: Preparation of poly(4-vinylpyridinium permanganate)s and their use as oxidizing reagents

Crosslinked poly(4-vinylpyridine) and poly(4-vinylpyridine-co-styrene) were functionalized with permanganate group to afford the corresponding poly[4-vinyl(pyridinium permanganate)] resin. These resins were found to selectively oxidize alcohols to corresponding carbonyl compounds. These insoluble functionalized polymers possess the desired characteristics of the polymeric reagents, including operational simplicity, filterability, and regenerability. The influence of solvent, duration of reaction, and molar excess of the reagent in these oxidation reactions was investigated to find out the optimum conditions for effective oxidation reactions. The reactions were found to be more facilitated in nonpolar solvents, and a large excess of the polymeric reagent did not have any significant effect on the extent of reactions. The poly[4-vinyl(pyridinium permanganate)] resin bears a contrast to KMnO₄ and other polymer-supported oxidizing agents like poly[4-vinyl(pyridinium chlorochromate)] in that it does not bring about the oxidation of the alcohol group directly attached to the ring structure.     

Gradient Semiinterpenetrating Polymer Networks Based on Polyurethane and Polyvinylpyrrolidone

Common and gradient semiinterpenetrating polymer networks based on polyurethane and polyvinylpyrrolidone were prepared. The physicomechanical and IR spectroscopic parameters of these networks were determined and compared.     

Prediction of excess thermodynamic functions and activity coefficients of some polymeric liquid mixtures using a new equation of state

In this work, the excess thermodynamic properties, namely excess molar Gibbs energy, excess molar enthalpy, excess molar entropy, excess molar internal energy, and excess molar Helmholtz energy for four polymer mixtures and blends at different temperatures, pressures, and compositions have been calculated using the GMA equation of state. We have also calculated the activity coefficient for these polymeric mixtures using the GMA equation of state. The values of statistical parameters between experimental and calculated properties show the ability of this equation of state in reproducing and predicting the excess thermodynamic functions and activity coefficients for studied polymeric mixtures.     

聚酯基硫脲树脂PDTU—I对Ag（I）的吸附性能研究

测定了聚酯基硫脲树脂对银离子的吸附容量,讨论了吸附时间、溶液酸度,温度及银离子初始浓度等因素对其吸附性能的影响,并对吸附动力学和热力学进行了研究。结果表明,树脂对Ag(I)的吸附遵循G.E.Boyd液膜扩散方程和Langmuir等温式,且吸附为吸热过程。     

Adsorption of aromatic compounds on porous covalent triazine-based framework

Covalent triazine-based frameworks (CTFs) are an emerging class of polymers whose adsorption properties of organic chemicals are not well understood. The main objective of this work was to evaluate combined effects of the functional groups of aromatic solutes and the triazine structure of a synthesized CTF on adsorption in aqueous solutions. Adsorption of the hydroxyl-, amino-, nitro-, and sulfonate-substituted monocyclic and bicyclic aromatic compounds was generally stronger than their non-substituted, nonpolar counterparts (benzene and naphthalene). When compared with Amberlite XAD-4 resin, one of the most common and widely used polymeric adsorbents, the CTF showed much stronger adsorption toward the polar and/or ionic compounds. To explain the adsorption enhancement of CTF, several specific, non-hydrophobic mechanisms were proposed, including hydrogen bonding (hydroxyl- and amino-substituted compounds), electrostatic attraction (anionized compounds), and π-π electron-donor-acceptor (EDA) interaction (nitroaromatic compounds) with the triazine structure of CTF. The hypothesized mechanisms were further supported by the observed pH dependence of adsorption. Resulting from size exclusion, adsorption of large-size dissolved humic acids on the homogeneous, nanopored (1.2 nm in size) CTF was negligible and did not affect adsorption of aromatic solutes. Additional advantages of fast adsorption/desorption kinetics and complete adsorption reversibility made CTF a superior adsorbent for aromatic compounds.     

MODIFICATION OF X-5 RESIN AND ADSORPTION PROPERTY OF THE MODIFIED RESINS

1. INTRODUCTION Adsorption capacity and selectivity are improved when some ion exchange groups or hydrogen bonding acceptor or/and donors are introduced into common polymeric adsorbents [1~5]. R. F. Shi et al have synthesized a series of bifunctional ads…     

Characterisation of UV-cured acrylate networks by means of hydrolysis followed by aqueous size-exclusion combined with reversed-phase chromatography

UV-cured networks prepared from mixtures of di-functional (polyethylene-glycol di-acrylate) and mono-functional (2-ethylhexyl acrylate) acrylates were analysed after hydrolysis, by aqueous size-exclusion chromatography coupled to on-line reversed-phase liquid-chromatography. The mean network density and the fraction of dangling chain ends of these networks were varied by changing the concentration of mono-functional acrylate. The amount and the molar-mass distribution of the polyethylene-glycol chains between cross-links (M(XL)) and polyacrylic acid (PAA) backbone chains (the so-called kinetic chain length (kcl)) in the different acrylate networks were determined quantitatively. The molar-mass distribution of kcl revealed an almost linear dependence on the concentration of mono-functional acrylate. Analysis of the starting materials showed a significant concentration of mono-functional polyethylene-glycol acrylate. In combination with the analysis of the extractables of the UV-cured networks (polymers not attached to the network, impurities that originate from the photo-initiator and unreacted monomers), more insight in the total network structure was obtained. It was shown that the UV-cured networks contain only small fractions of residual compounds. With these results, the chemical network structure for the different UV-cured acrylate polymers was expressed in network parameters such as the number of PAA units which are cross-linked, the degree of cross-linking, and the network density, which is the molar concentration of effective network chains between cross-links per volume of the polymers. The mean molar mass of chains between chemical network junctions (M(C)) was calculated and compared with results obtained from solid-state NMR and DMA. The mean molar mass of chains between network junctions as determined by these methods was similar.     

EFFECT OF pH ON THE ADSORPTION OF p-AMINOBENZOIC ACID ON POLYSTYRENE-BASED ADSORBENTS

In the present study the adsorptive properties of p-aminobenzoic acid with hypercrosslinked and multi-functional polymeric adsorbents at different solution pHs were systematically investigated in accordance with the particular physicochemical characteristics of the aromatic amphoteric compound involving both Lewis acid and Lewis base functional groups. It was found that the equilibrium adsorption data of the three polymeric adsorbents fitted well in the Langmuir and Freundlich isotherm equations. Studies at various pH levels indicate that the capacity of the adsorbents for adsorption of the ionic forms of adsorbate is less than that for the corresponding neutral species. At pH 3.78, the adsorption capacities of the three adsorbents are the highest. Whereas the adsorption property of multi-functional polymeric adsorbent NJ-99 is the largest, which may be attributed to the strong hydrogen-bonding interaction between the amino groups on the resin and the carboxyl group of p-aminobenzoic acid. The trend of the adsorption capacities of the three adsorbents towards p-aminobenzoic acid with the solution pH is in accord with the dissociation curve of the neutral molecular p-aminobenzoic acid. The adsorption forces include π-π interaction, hydrogen-bonding interaction and electrostatic attraction or repulsion when there exist the molecular and ionic adsorbing species at different pHs in aqueous solution.     

MODIFICATION OF X-5 RESIN AND ADSORPTION PROPERTY OF THE MODIFIED RESINS

Three polymeric adsorbents with hydrogen bonding acceptors, methylamine,N-methyl-acetamide and aminotri(hydroxymethyl)methane modified resins are synthesized fromchloromethylated X-5 resin. Adsorption isotherms of phenol and theophylline onto the three modifiedresins and the original X-5 resin from aqueous solution are measured. The results show thatadsorption of compounds with hydrogen bonding donor onto methylamine and N-methylacetamidemodified resins is enhanced as compared with that onto X-5 resin, and adsorption mechanismbetween the adsorbents and the adsorbates is mainly based on hydrogen bonding and hydrophobicinteraction. While adsorption of compounds with hydrogen bonding donor ontoaminotri(hydroxymethyl)methane modified resin is lowered as compared with that onto X-5 resin, andadsorption mechanism between the adsorbent and the adsorbates is mainly based on hydrophobicinteraction.     

Adsorption of oligomeric polyamineimide binder and its monomers on the surface of nonstoichiometric compounds of titanium

Adsorption of an oligomeric polyaminoimide binder, PAIS-104, and its monomers, diaminodiphenylmethane and dimaleimidodiphenylmethane, on the surface of nonstoichiometric titanium carbides, nitrides, and carbonitrides was studied. The dependence of the oligomer adsorption parameters and strength properties of composites on the nature, composition, and specific surface area of the adsorbent and presence of various additives in the binder was examined.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1647–1653.Original Russian Text Copyright © 2004 by Ishkov, Sagalakov.