High Concentration Of Functional Groups Research Articles

Soybean-Based Bio-Adhesives: Role of Diamine on the Adhesive Properties.

One possible approach to achieving sustainable development in the materials sector is to produce polymers from plant oils (POs), which are renewable and environmentally beneficial. Polymers with a high concentration of functional groups can be used as cross-linking agents to enhance the properties of epoxidized POs (epoxidation of plant oil)-based polymers. In this work, a unique resin with novel properties and potential uses was produced by cross-linking epoxidized soybean oil (ESO) with branched and flexible polyamines by ring-opening and amidation polymerizations. This approach is straightforward and ecologically benign. After curing, melamine pentane diamine (MPD) polymer maintained its position as the strongest structural adhesive among the synthesized resins, with a bonding strength of almost 2000 kPa for stainless steel; irrespective of the temperature, stainless steel consistently outperforms melamine ethylene diamine-ESO resin in strength comparisons. At 100 °C, stainless steel has a lap shear strength of about 300 kPa, which is far higher than copper and aluminum; at 180 °C, this value increases by another 750 kPa. While MPD-ESO resin has a shear strength of 1996 kPa at 180 °C, melamine butane diamine-ESO resin has a shear strength of only 1220 kPa.

Development of Porous Cobalt-/Copper-Doped Carbon Nanohybrids Derived from Functionalized MOFs as Efficient Catalysts for the Ullmann Cross-Coupling Reaction: Insights into the Active Centers.

Newly emerging poly-functional metal-organic frameworks (MOFs) have been proved to be a promising alternative method for the hard/soft template to generate different carbon-based heterostructures. Herein, we have synthesized a sulfonyl-amide-based MOF (TMU-81) with an exceptionally high concentration of functional groups, which can interact strongly with metal ions and utilized it as a double-template platform to fabricate versatile catalysts by remaining structural regularity. The preloaded copper ions resided in pores of TMU-81 not only play a significant role in pore-forming by in situ renovating into Cu nanoparticles via the pyrolysis process but also trigger the morphological transformations of the resultant metal/carbon hybrids. The morphology of the TMU-81 was tuned from truncated octahedron to cubic in cobalt-/copper-doped carbon nanohybrids (MC-81), and also the Brunauer-Emmett-Teller surface area increased significantly up to 1450 cm2/g. Benchmarks have been established for the performance of TMU-81, pyrolyzed TMU-81 (P-TMU-81), and MC-81s, as efficient and robust catalysts for the C-N cross-coupling reaction with aryl-halides and amines. The obtained MC-81 showed superior performance compared with pristine TMU-81 and pyrolyzed P-TMU-81. The catalysis performance is found to be closely dependent on the amount of preloaded Cu2+ ions in the MOFs. After 5 cycles, the catalysts were reusable without any significant loss of activity. Benefiting from the structural and compositional advantages, the present approach offers an intelligent way to synthesis and design of structurally complex MOF hybrid and derived functionalized systems.

Reduced graphene oxide nanosheets doped by Cu with highly efficient visible light photocatalytic behavior

Abstract Graphene oxide (GO) and reduced graphene oxide (RGO) exhibit good electrochemical properties due to their semiconducting nature, large surface area, high concentration of functional groups and unique layered structure. They have been used widely for the removal of heavy metal ions, dyes and other organic contaminants from water. In the present study, a modified Hummer’s method was used to prepare GO while Cu-doped RGO which was obtained by employing a simple hydrothermal process. X-ray diffraction analysis confirmed the presence of GO sheets and Cu-doped RGO in the synthesized product. Examination with field emission scanning and high resolution transmission electron microscopes revealed an ultrathin, porous and layered structure of GO nanosheets while RGO sheets appeared as a well-defined, layered and non-agglomerated sponge. Dispersion of Cu within RGO sheets was also confirmed during microstructural study. Optical properties, such as absorption of light and bandgap width, were studied using UV–visible spectroscopy. Photoluminescence characterization showed maximum emission between 300 and 350 nm (UV region) caused by the presence of vacancies and surface defects in synthesized sheets. In aqueous media, methylene blue (MB) pollutant was photodegraded up to 91% within 80 min when Cu-doped RGO photocatalyst was employed under visible light irradiation. The present work shows the ability of Cu-doped RGO to degrade aqueous pollutants in an efficient manner. In conclusion, this product can find potential application in the removal of organic pollutants from wastewater.

Mechanical properties of graphene oxide: The impact of functional groups

In the current study, mechanical characteristics of graphene oxide (GO) as a promising substitute of graphene are systematically studied through molecular dynamics simulation. For this purpose, several GO samples having different concentrations of epoxide and hydroxyl functional groups are considered. The results reveal that increasing the epoxide coverage causes a noticeable deterioration in the mechanical characteristics of GO systems. This change is correlated with the increase of the formation of ripples in the structure upon increasing the epoxide coverage. Moreover, investigating the bond lengths in the system, it is concluded that the higher epoxide percentage leads to an increase in the length of single and hybrid resonance bonds leading to an overall deterioration of the mechanical properties of GO samples. Additionally, our results demonstrate that high concentration of functional groups can lead to a negative Poisson’s ratio. Increasing the amount of hydroxyl groups shows the same declining effect on the Young’s modulus. In a graphene system containing both epoxide and hydroxyl groups, it is deduced that a higher percentage of the former can result in a higher residual strain because of the formation of more ripples within the system.

Preparation of water-soluble β-cyclodextrin/poly(acrylic acid)/graphene oxide nanocomposites as new adsorbents to remove cationic dyes from aqueous solutions

Abstract Novel nanocomposites of β-cyclodextrin/poly(acrylic acid) grafted onto graphene oxide (β-CD/PAA/GO) were successfully synthesized for the first time using an esterification reaction, and they were used to remove the cationic dyes methylene blue (MB) and safranine T (ST) from aqueous solutions. The as-prepared β-CD/PAA/GO nanocomposites were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The β-CD/PAA/GO nanocomposites showed excellent water dispersibility because of the hydrophilicity of the polymer. The adsorption isotherms fitted the Langmuir isotherm model. The maximum adsorption capacities were 247.99 mg g −1 for MB and 175.49 mg g −1 for ST, and these are much higher than those of other carbon-based adsorbents that have been described in the literature. This was attributed to the high concentration of functional groups in the nanocomposites. Repeated MB and ST adsorption and desorption cycles showed that the β-CD/PAA/GO nanocomposites could be used repeatedly, and their adsorption capacities did not change significantly after five cycles. The fast and efficient adsorption of MB and ST by the β-CD/PAA/GO nanocomposites from aqueous solutions suggested that these novel nanocomposites may be ideal candidates for removing dyes during water treatment.

One-pot synthesis of amino functionalized mesoporous silica materials: using simulations to understand transitions between different structures

The rich phase behavior of surfactants can be exploited to design materials with a given desired structure and properties. One example includes amino functionalized mesoporous silicas, which can be used in different environmental applications, including removal of heavy metals from water and CO2 separation and purification. These applications may require a high concentration of functional groups, but the increased concentration of hybrid organic–inorganic precursors can lead to the destruction of the liquid crystals or transformation into other phases. In this work, we modeled the phase behavior of such systems using lattice Monte Carlo simulations and analyzed the distribution of hybrid organic–inorganic precursors to explain the observed changes in the liquid crystal structures. In particular, we observed that if the hybrid precursor is sufficiently hydrophobic, it can act as a cosurfactant, swell the core of the surfactant liquid crystal, and lead to structures with smaller interfacial curvature. On the other hand, if the hybrid precursor acts as a cosolvent it will solubilize the surfactant leading to the destruction of the preformed liquid crystal.

Organic groups functionalised mesoporous silicates

Great interests have been imparted on organically modified mesoporous silica materials due to their high surface areas, uniform pore sizes and integrated functionality. Besides the inherent character of inorganic and organic components, the interactions between them should also be recognised for the synthesis, including organic-group loading, mesostructure and particle morphology, condensation, as well as organic-group distribution. To obtain long range ordered hybrid materials, several factors, such as relative hydrolysis and condensation rates of the inorganic and organic sources, chemical character such as hydrophobicity/hydrophilicity and acid/base of organic ligand as well as the surfactant category, should be surveyed. A concept of 'combinatorial synthesis' is introduced here for the cases of combining two or more functional units in a typical synthesis into a single one. The silica precursors in the preparation of periodic mesoporous organosilanes (PMOs) are the aggregation of inorganic and organic silicates. The assembly will lead to a unique distribution and high concentration of functional groups. Both the confinement within the mesopores and the pore surface nature will affect the accessibility to the active sites, and therefore, the adsorption and relative applications. These characters win them ample host-guest chemistry. They can seek the opportunities in the fields of catalysis, separation, electronic devices, biomedicines, nanomaterial fabrication, etc.

A theoretical explanation for the retention mechanism of ion exclusion chromatography

AbstractIon Exclusion Chromatography is classically used for the separation of weak acid anions. Dilute strong acids (e.g. sulphuric or perchloric acid) or just water are used as eluents. To increase the exclusion effect, strong cation exchangers, characterized by high concentration of functional groups, are applied. The inner column volume of commercially available columns is increased by increasing their size in comparison to traditional ones (usually 300×7.8 mm ID). The description of the retention mechanism of this technique implicitly assumes that both mobile and stationary phases are typical aqueous solutions, and their dielectric constants are thus equal. This equality implies the equality of solute dissociation constants in both phases. Another implicit assumption is that the dead‐ and inner volumes of the column are constant, and independent of the mobile phase composition. The present paper shows that stationary and mobile phases are generally characterized by different physicochemical parameters. Thus, they cannot be considered as regular aqueous solutions. Additionally, we show that weak cation exchanger resins, which are characterized by a relatively small concentration of the functional groups, and weak acid based buffers can also be used in IEC. This would expand the possible applications of this method and enable, for example, the separation of strong acids (anions). The influence of ionic strength on the retention and dead‐ and inner column volumes is also discussed. Finally we also briefly describe the retention mechanism of Electrostatic Ion Chromatography.

Reaction ability of heterochain complex-forming organopolymeric and organosilicon S-, N-containing sorbents toward noble metals

Organopolymeric and organosilicon heterochain complex-forming sorbents containing aliphatic thioether or (and) weakly basic amino groups or the complex selective analytical groups are highly effective sorbents for selective recovery and concentration of noble metals. They are characterized by high values of distribution coefficients and sorption capacity for noble metals owing to high concentration of functional groups in the polymeric chain (Table 1, 2). The mechanism of sorption of some noble metals from hydrochloric (Pd (II), Pt (IV), Rh (III), Au(III)) and nitric (Pd (II), Ag (I)) solutions by heterochain sorbents of net, linear and cyclic structure is discussed. It was shown, that mechanism of the interaction of metals ions with functional groups of sorbents and the type of generated sorption complexes are defined by the nature of electron-donor atoms and the metal, by the structure of the functional groups and their state depending on the acidity of solution, by equilibrium of complexation and hydrolysis of complex metal forms in solution as well by the composition of solution. Selectivity and the rows of sorption affinity of S-; S,O- and S,N-containing sorbents are in agreement with the concept of hard and soft acids and bases.

Protein adsorption on novel acrylamido-based polymeric ion-exchangers: I. Morphology and equilibrium adsorption

The protein uptake equilibrium and particle morphology are determined for novel polymeric ion-exchange media based on acrylamido monomers with a high density of functional groups and a variety of morphological characteristics. The study considers two anion-exchangers and a cation-exchanger. Physical properties determined experimentally include particle density, ion-exchange capacity, particle size distribution, and equilibrium isotherms for model proteins. The pore structure was evaluated using size exclusion chromatography with neutral probe molecules and transmission electron microscopy. For the anion-exchangers, two types of structures were inferred. The first is comprised of particles that contain a low-density gel supported by denser polymer aggregates. This material had a very low size-exclusion limit for neutral probes, but exhibited an extremely high and reversible protein adsorption capacity (280–290 mg BSA/ml). The second structure is comprised of particles with large, open macropores. While the size-exclusion limit was very high, the protein adsorption capacity was low (60 mg BSA/ml). Moreover, the adsorption was nearly irreversible. The physical structure of the cation-exchanger appeared to be intermediate between those of the anion-exchangers, containing both large pores and smaller pores yielding an intermediate, but reversible, protein uptake capacity (120–130 mg αCHY/ml). The different behavior of these materials with regards to protein adsorption correlates well with their physical structure. For these ion-exchangers, high protein adsorption capacities are attained when a low-density polymer gel with a high concentration of functional groups is present.

A GENERAL SURVEY OF THE PROPERTIES OF A NEW CLASS OF FUNCTIONALISED MATERIALS WITH ORGANOPOLYSILOXANE STRUCTURE

ABSTRACT The metal sorption properties of a series of 14 functionalised organopolysiloxanes are reported. Such materials have been synthesized at DEGUSSA by polycondensation of suitably bifunctional silane monomers. The corresponding functional groups or combination of functional groups are : -SH; -S-; -SH + -S-; -NH- + -S-; -NH-[CH2] 2-NH2; -N=CH-C5H4N; -N=CH-C8H4OH; -NH-C[=S]-NH-; -NH-C[=S]-N[-]-[CH2] 2-N[CH3] 2; -NH-C[=S]-N[-]-C[=O]-C8H5; -NH-C[=S]-S-; -P[C8H5]-; -P[C8H5] 2 and -SO3H. Such materials appear as spherical or egg-shaped solid particles with a grain size of about 0.1 to 1.5 mm and surface areas up to 700 m2 / g. They are composed of a siliceous core and contain a high concentration of functional groups which, moreover, are bound to the matrix via carbon-silicon bonds which are fairly stable towards hydrolysis. They can therefore be safely used over a large range of acidities : i.e. from [HCI] > 6 mol / L up to about pH 11 or 12. The main advantages of the new functionatised organopolysiloxa...

Distribution of graft poly (methacrylic acid) in polyester fiber.

For introducing high concentration of functional groups on the surface of polyester fibers, thin layer grafting of methacrylic acid (MA) was applied to polyester fiber by direct electron irradiation. Radial distribution of concentration of MA in the thin surface layer of the grafted fiber was examined by measuring the optical reflectivity of the surface dyed after concecutive alkali hydrolysis of the grafted fiber.By the alkali treatment of graft fiber it became clear that the concentration of MA was relatively low on the fiber surface, showed a maximum at the inner part within 1μm from the surface, and then decreased toward the inner regions of the fiber.From above results we expect that by shaving the surface by a proper quantity through alkali treatment and thus exposing the surface with the maximum concentration of functional group, we can give a high concentration of functional groups at the surface of polyester fibers. Actually MA graft polyester fibers showed excellent dyeability by grafting even below 1%, through alkali treatment.