Peripheral Hydroxyl Research Articles

Unlocking the full potential of citric acid-synthesized carbon dots as a supercapacitor electrode material via surface functionalization.

This research paper investigates the effect of functionalizing the surfaces of citric acid-synthesized carbon dots (CDs) with hyperbranched bis(methylol)propionic acid (bis-MPA) polyester hydroxyl polymers (HBPs) on their performance as electrode materials in a supercapacitor. Two types of HBPs with 16 and 64 peripheral hydroxyl groups were used to functionalize the CDs' oxygen-enriched surface. Here, CDs were used as electrode materials for the first time in symmetric supercapacitors without a composite material, and how surface modification affects the capacitance performance of CDs was investigated. Our results showed that the functionalization of green-emitting CDs with HBP resulted in the successful passivation of surface defects, which improved their stability and prevented further oxidation. The CDs with HBP passivation exhibited excellent electrochemical performance, with a high specific capacitance of 32.08 F g-1 at 0.1 A g-1 and good rate capability, indicating a faster ion transport rate at high current densities. Experimental EPR spectra of functionalized and non-functionalized CDs reveal distinct changes in g-factor values and line widths, confirming the impact of dangling bonds and spin-orbit interactions. The observed broader linewidth indicates a wider range of electron spin resonances due to energy-level splitting induced by spin-orbit coupling. The excellent electrochemical performance of CDs with HBP passivation can be attributed to the presence of oxygen-containing surface functional groups such as hydroxyl and carboxyl groups on their surfaces, which enhance the conductivity and charge transfer reactions. These results suggest that functionalization with polar HBPs is a promising strategy to enhance the electrochemical performance of CDs in supercapacitor applications.

Luminescent lanthanide-based chemodosimeter for selective detection of G-series nerve agent simulant with multiple reactive sites

The strongly chelated luminescent LnIII-based optical probes: [Ln(dipicOH)3]3- [Ln = EuIII (1), TbIII (2)], decorated with multiple reactive peripheral hydroxyl groups were strategically designed for the selective detection of diethyl chlorophosphate (DCP), a simulant of sarin (GB) nerve agent. Their reaction results in the modulation of antenna effect and/or ligand-exchange reactions as reflected in the quenching of the 5DJ-7FJ transitions of respective LnIII probes.

Extraordinary behavior of 5-(3,4-dihydroxyphenyl)-10,15,20-tris(N-methylpyridinium-3-yl)porphyrin triiodide in titration with bases and in albumin oxidation

The observed rate constants of the photoinduced oxidation of albumin increased by a factor of 1.5–2 upon deprotonation of the peripheral hydroxyl groups of 5-(3,4-dihydroxyphenyl)-10,15,20-tris(N-methylpyridinium-3-yl)porphyrin triiodide compared to its phenolic form.

Janus-Type Dendrimers Based on Highly Branched Fluorinated Chains with Tunable Self-Assembly and 19F Nuclear Magnetic Resonance Properties

Tuning the self-assembly of dendritic amphiphiles represents a major challenge for the design of advanced nanomaterials for biomimetic applications. The morphology of the final aggregates, in fact, critically depends on the primary structure of the dendritic building blocks as well as the environmental conditions. Here we report a new family of fluorinated Janus-type dendrimers (FJDs), based on a short-chain and branched fluorinated synthon with 27 magnetically equivalent fluorine atoms, linked to bis-MPA polyester dendrons of different generations. Increasing size, flexibility, and number of peripheral hydroxyl groups, we observed a peculiar self-assembly behavior in bulk and in aqueous media as a consequence of the subtle balance between their fluorinated and hydrophilic portions. The lowest generation FJDs formed spherical nanoparticles in water, e.g., micelles, showing a single 19F NMR peak with good signal-to-noise ratio and over time stability, making them promising as 19F-MRI traceable probes. The highest generation FJD, instead, presented an interesting morphological transition from multilamellar dendrimersomes to tubules as a consequence of a subtle balance of intra- and intermolecular forces that compete at the interface. Interestingly, a reduction of the local mobility of CF3 groups passing from dendrimersomes to tubules switches off the 19F NMR signal. The transition mechanism has been rationalized by coarse-grain simulations as well as demonstrated by using cosolvents of different nature (e.g., fluorinated) that promote conformational changes, ultimately reflected in the self-assembly behavior. Short and branched fluorinated chains have here been demonstrated as new moieties for the design of FJDs with tunable self-assembly behavior for potential applications as biocompatible 19F MRI probes in the construction of theranostic platforms.

Dendritic core derived unimolecular micelles with poly(lactic acid) arms: Synthesis and application as a phase transfer agent

AbstractUnimolecular micelles refer to amphiphilic hyperbranched molecules, which exhibit micellar characteristics in a single molecule. In the present study, starting with pentaerythritol, three new dendrimers D1, D2, and D3 were synthesized in good yields bearing 9, 12, and 18 peripheral hydroxyl groups, respectively, using alkyne‐azide Husigen 1,3‐dipolar cycloaddition reaction. The structural integrity and purity of the dendrimers were confirmed by 1H and 13C NMR spectroscopy, and FE‐SEM studies established their near‐spherical morphology. Using D2 as a macroinitiator, hyperbranched 12‐arm star polymers were synthesized via ring‐opening polymerization of l‐lactide. The star polymer is found to be an efficient sequestering agent for water‐soluble dyes like congo red, bromophenol blue, and methyl orange from aqueous phase due to its amphiphilic nature demonstrating the application of unimolecular micelles in dye removal from aqueous waste.

Surface modification of TiO2 nanoparticles with 1,1,1-Tris(hydroxymethyl)propane and its coating application effects on castor seed oil-PECH blend based urethane systems

Surface modification of peripheral hydroxyl groups of TiO2 with trimethylolpropane (TMP) was successfully carried out and characterized. This hybrid material (TiO2-TMP) was added in percentages to a polyol blend of castor seed oil (a renewable resource and nontoxic material) and poly(epichlorohydrin)-triol (PECH-triol) {a cross-linker}. After ultrasonication of the polyol blend with TiO2-TMP, through a one-pot synthesis, the mixture was made to react with polymeric 4,4′-methylene diphenyl diisocyanate (PMDI) using 4-Methyl-2-pentanone as a reacting solvent. The synthesized PECH-triol and composite coating films structural elucidation was carried out using FTIR, 1H NMR and 13C NMR. The pristine/undoped and composite films were subjected to specific coating evaluations such as morphology (FESEM), XRD, thermal stability, mechanical property (UTM), chemical resistance, antimicrobial activity and corrosion resistance (Tafel plot). The doped composites showed improved coating properties, especially PU-TiO2-TMP (1.0 wt%), which possesses the highest percentage of TiO2-TMP nanoparticle.

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

Biodegradable and Biocompatible Silatrane Polymers.

In this study, new biodegradable and biocompatible amphiphilic polymers were obtained by modifying the peripheral hydroxyl groups of branched polyethers and polyesters with organosilicon substituents. The structures of the synthesized polymers were confirmed by NMR and GPC. Organosilicon moieties of the polymers were formed by silatranes and trimethylsilyl blocks and displayed hydrophilic and hydrophobic properties, respectively. The effect of the ratio of hydrophilic to hydrophobic organosilicon structures on the surface activity and biological activity of macromolecules was studied, together with the effect on these activities of the macromolecules’ molecular weight and chemical structure. In particular, the critical micelle concentrations were determined, the effect of the structure of the polymers on their wetting with aqueous solutions on glass and parafilm was described, and the aggregation stability of emulsions was studied. Finally, the effect of the polymer structures on their antifungal activity and seed germination stimulation was examined.

Novel polymer surfactants based on the branched silatrane-containing polyesters and polyethers

Objectives. Biologically active polymeric surfactants are a new promising class of macromolecules that can find application in medicine, cosmetology, and agriculture. In this study, a number of new biologically active amphiphilic polymers based on branched silatrane-containing polyesters and polyethers were obtained, and their surface-active properties were investigated.Methods. The branched polymers were represented by polyethers and polyesters, obtained respectively via the anionic polymerization of 1,2-epoxypropanol or a combination of equilibrium polycondensation and ring opening polymerization. The polymers were modified with 3-isocyanopropylsilatrane and trimethylethoxysilane to obtain the amphiphilic compounds containing silatrane groups bonded to the polymer backbone by the urethane bond. The structure of the synthesized polymer silatranes was confirmed via nuclear magnetic resonance spectroscopy and gel permeation chromatography. The surface active properties of all the copolymers obtained were investigated in connection with their obvious amphiphilicity. In particular, the formation of micelles in aqueous solutions is such a property. The critical micelle concentrations were determined by a method of quenching the fluorescence of the polymers.Results. It was shown that the values of the critical micelle concentrations and the hydrophilic-lipophilic balance values of polymers determined by the Griffin equation correlate well with each other. A linear relationship between the hydrophilic-lipophilic balance and the critical micelle concentrations was established. At the same time, polyether-based polymers generally showed higher critical micelle concentrations than polyester-based polymers, although the hydrophilic-lipophilic balance values for polymers of different series, but with close degrees of substitution, were close. It was found that the use of all synthesized polymers as stabilizers of direct and reverse emulsions leads to an increase in the aggregative stability of both types of emulsions. The stability of emulsions depended both on the degree of substitution of peripheral hydroxyl groups of polymers by silatranes and on the molecular weight and structure of the branched block of polymers. The stability of direct emulsions increased for all polymers, while that of inverse emulsions decreased with an increasing degree of substitution of hydroxyl groups by silatranes. The increase of the branched block molecular weight led to an increase of droplet sizes for both direct and inverse emulsions. The smallest droplet size for direct and inverse emulsions was obtained using polymers with low molecular weight branched polyester blocks as surfactants.Conclusions. The results obtained prove the possibility of creating polymer surfactants containing silatrane groups. By varying the structure of the polymer, its molecular weight and the degree of substitution of peripheral functional groups, it is possible to obtain surfactants with desired surface properties.

Water-soluble polyglycerol-dendronized poly(norbornene)s with functional side-chains.

High molecular weight polyglycerol-dendronized poly(norbornene)s (PGD-PNBs) were prepared via ring-opening metathesis polymerization of norbornene monomers containing amine functional groups on the side-chains followed by dendron growth from the olefins of PNB backbones using iterative dihydroxylation and allylation. The fourth-generation PGD-PNB with a degree of polymerization of ca. 500 is thus functionalized with 16 peripheral hydroxyl groups as well as a single amine on each repeat unit of the PNB backbone. Furthermore, the amine functionality could be used to install hydrophobic fluorophores such as coumarin and pyrene, thereby obtaining the final PGD-PNB structures which are highly water-soluble and fluorescent.

Trifunctional metal-organic platform for environmental remediation: structural features with peripheral hydroxyl groups facilitate adsorption, degradation and reduction processes.

A Cd(ii)-based metal-organic framework (MOF) {[Cd(PA)(4,4'-bpy)2](H2O)}n (where, PA = pamoic acid, and bpy = bipyridine) has been demonstrated to have trifunctional properties, namely as (i) an efficient and selective adsorbent for dyes, (ii) a visible-light-active photocatalyst for the degradation of dyes and (iii) a photocatalyst for Cr(vi) reduction. Hence, this material has a very good potential for application in environmental remediation. In particular, the MOF exhibits excellent selectivity toward cationic methylene blue (MB) dye adsorption and its separation over neutral (neutral red) and anionic (methyl orange) dyes. In addition, the catalyst has also been explored for the photocatalytic degradation of less adsorbed dyes, such as methyl orange (MO) and rhodamine B (RhB). Subsequently, the potential of the presented MOF for the photocatalytic reduction of Cr(vi) under visible light irradiation has also been investigated and the catalyst was found to reduce 95% of Cr(vi) within 3 h. Moreover, simultaneous one-pot photocatalytic reduction of Cr(vi) and dye degradation has been demonstrated with high efficiency using the same catalyst. The mechanism of adsorption could be correlated to the presence of peripheral hydroxyl groups in the MOF and the photocatalytic activity observed under visible light could be attributed to the optical properties of Cd-MOF. In principle, this work could broaden the utilization of single metal organic platform for multifunctional applications toward environmental remediation.

Cellulose-graphene quantum dot composite membranes using ionic liquid

Selective separation of small molecules by membranes is inhibited by the performance gap between nanofiltration and ultrafiltration membranes. In this work, a membrane that can efficiently remove small molecules (> 300 Da) was created by incorporating graphene oxide quantum dots (GQDs) into a cellulose membrane using an ionic liquid (1-ethyl-3-methylimidazolium acetate). Incorporation of GQD into cellulose membranes using an ionic liquid brings several advantages over traditional mixed matrix membranes: 1) GQDs are abundant in peripheral hydroxyl and carboxyl groups, thus GQDs have strong binding with cellulose through hydrogen bonding and forms a stable composite membrane. 2) Negative surface charge of GQDs helps prevent aggregation. 3) The size (5 nm) of GQD is smaller than most nanoparticles used in membranes, allowing for interesting pore forming properties. GQD-cellulose membranes were prepared by non-solvent induced phase separation in water. It was determined that about 45% of GQDs are incorporated from solution to membrane. GQDs were determined to be located on the membrane surface, giving the membrane negative surface charge and improved hydrophilicity. GQDs showed no leaching after convective flow through the membrane. Impact of GQD on membrane permeability and rejection was studied through convective flow experiments, and through longer term permeability studies.

N,N,N-Tris(tert-butoxycarbonyl)-l-arginine: five isoforms whose obtainment depends on procedure and scrupulous NMR confirmation of their structures

l-arginine is often covalently linked to vectors for gene or drug delivery as a means of increasing their transfection activity and reducing toxicity. This strategy relies on the protection of basic nitrogen atoms, for example, by employing the tert-butoxycarbonyl group. Our aim in the present work was to prepare the widely described α N, ω N, ω′ N-tris(tert-butyloxycarbonyl)-l-arginine as a single isomer in high yield and with high levels of purity for use in the esterification of dendrimers with several peripheral hydroxyl groups. Following three reported protocols which assured this goal, we observed the unexpected formation of four additional isomers. Using the first procedure, α N, ω N, ω′ N-tris(tert-butyloxycarbonyl)-l-arginine was never obtained. The second procedure delivered the desired compound as a mixture of geometric isomers (E/Z), while the third protocol led to a single isomer in high yield and purity, but with an unreported symmetrical structure. Since Boc protection is transient, this discovery would seem to be of little interest, but preliminary results from an ongoing investigation of the behavior of each of the isomers obtained in the esterification reactions of interest has shown that their reactivity depends on their structure. Although this research is ongoing, here we report a detailed description of these unexpected results, along with an NMR investigation focusing on the double-bond geometry and position which enabled confirmation of the structures.

Synthesis and characterization of polyester-based dendrimers containing peripheral arginine or mixed amino acids as potential vectors for gene and drug delivery

Macromolecular systems with well-defined sizes, shapes and high controlled architecture like dendrimers are of eminent interest in nanomedical applications such as drug delivery, gene transfection, and imaging. In this paper versatile protocols for the synthesis of polyester-based, hydrolysable, polycationic dendrimers have been setup. Fourth and fifth generation dendrimers equipped with several peripheral hydroxyl groups were prepared from 2, 2-bis(hydroxymethyl)propanoic acid. They were successfully esterified with arginine alone or mixed with lysine or O-methyltyrosine and with dipeptide arginine-glycine and seven polycationic dendrimers were finally obtained as hydrochlorides. Their structures and composition were confirmed by NMR analysis and by experimental molecular weight computed by volumetric titration and their buffer capacity was higher than fourth generation polyamidoamine (G4- PAMAM) derivatives taken as reference. The synthesized dendrimers harmonize a polycationic character and a buffer capacity which presuppose a good transfection efficiency with a degradable scaffold thus appearing as a promising team of new non-toxic vectors for biomedical applications.

Polymer/boehmite nanocomposites: A review

ABSTRACTBoehmite is an aluminum oxyhydroxide [AlO(OH)] which is preferentially used as precursor for the production of (transition) aluminum oxides. Boehmite alumina (BA) nanoparticles are available in various morphologies due to versatile synthesis routes, which are briefly introduced. The peripheral hydroxyl groups of BA offer manifold functionalization possibilities for tailoring the dispersion and filler/matrix adhesion properties. The incorporation of BA nanofillers, with and without surface treatments, may yield improved mechanical and novel functional properties in polymers. BA can be introduced in polymers and polymer composites through different methods. This comprehensive overview covers the basic results reported on polymer/BA nanocomposites in the open literature. In this review, polymer matrices are grouped into thermoplastics, thermosets, and rubbers. Using literature results and our own findings, we have identified promising R&D trends with polymer/BA nanocomposites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45573.

Control of the spatial arrangements of supramolecular networks based on saddle-distorted porphyrins by intermolecular hydrogen bonding

Supramolecular integration of a saddle-distorted zinc(II) porphyrin complex, which has hydroxyl groups at the para-position of the four meso-aryl groups, has been demonstrated on the basis of hydrogen bonding among the peripheral hydroxyl groups. The hydrogen-bonding patterns were controlled by the recrystallization solvents and additives, and particularly, addition of a bifunctional ligand such as 4,4'-bipyridine (bpy). The coordination of bpy to form dinuclear Zn(II)-porphyrin complexes causes a conformational difference: the dimeric complex with four hydroxyl groups is in an eclipsed form, however, a derivative without hydroxyl groups is in a staggered form due to the presence or absence of the intermolecular hydrogen bonding. In addition, the dimerization by the bpy coordination resulted in the expansion of the intermolecular space formed in the porphyrin networks, suggesting the potential to be applied for inclusion of guest molecules.

Dendritic surface functionalization of nanomaterials: controlling properties and functions for biomedical applications

A wide variety of nanomaterials have demonstrated promise in medical applications such as drug delivery and imaging. In these applications, the surface chemistry of the materials is critical as it plays an important role in determining the toxicity and biodistribution behavior of the material. We review here the functionalization of nanomaterials with dendrons as an efficient method to alter the surface chemistry of the materials, introducing new properties and functions. Described here is the functionalization of superparamagnetic iron oxide nanoparticles (SPIO) with dendritic guanidines to enhance their transport into cells for magnetic resonance imaging applications. The introduction of dendrons bearing peripheral hydroxyls, amines, guanidines, carbohydrates and Gd(III) chelates to polymer vesicles (polymersomes) is also described. These dendritic moieties allow for modulation of toxicity, cell uptake, protein binding, and contrast agent efficiency, while at the same time allowing the stabilities of the polymersomes to be maintained. Thus, this approach holds promise for the development of a wide range of multifunctional materials for pharmaceutical applications.

Synthesis and characterisation of hybrid materials based on gold nanoparticles and HBP hyperbranched polyesters: Preparation of ``volcano-rings'' nanostructures

This paper describes a comprehensive investigation on the synthesis and characterisation of hybrid materials based on gold nanoparticles assisted with pseudo G2, G3 and G4 generations of hyperbranched polymers (HBP) (Boltorn H20, H30, H40). Nanoparticles (NPs) were obtained via a wet chemical method by mixing HBP polymers and a gold precursor in N,N′Dimethylformamide (DMF) followed by reduction by hydrazine. The system has been evaluated with two HBP:gold molar ratios 1:1 and 1:10. The resulting hybrid materials were characterized using atomic force microscopy (AFM), transmission electron microscopy (TEM), UV–vis spectroscopy, X-Ray diffraction spectrometry (XRD) and attenuated total reflection Fourier transform infra-red spectroscopy (ATR-FTIR).The modified hybridization strategy clearly demonstrated that Boltorn possess unique interaction abilities with AuNPs. Well-defined and novel HBP-AuNPs hybrid materials were obtained mainly as a result of the interaction between the peripheral hydroxyl groups of HBP and the gold nanoparticles. In the hybrid nanomaterials synthesis process, volcano-nanorings structures were obtained on solid substrate during the reaction of HBP-G4-OH64 (Boltorn H40) with gold nanoparticles. These novel nanostructured hybrid materials could be used in medicine as specific nano-containers for different drug molecules.

Molecular Encapsulation in Pyrogallolarene Hexamers Under Nonequilibrium Conditions

Pyrogallol[4]arene is a macrocycle with a concave surface and 12 peripheral hydroxyl groups that mediate its self-assembly to form hexamers of octahedral symmetry in the solid state, in solution, and in the gas phase. These hexamers enclose approximately 1300 Å(3) of space, which is filled with small molecules. In this study, we show that solvent-free conditions for guest entrapment in these hexamers, using molten guest molecules as solvent and allowing the capsules to assemble during cooling, results in exceptionally kinetically stable encapsulation complexes that are not formed in the presence of solvent and are not thermodynamically stable. The capsules' kinetic stabilities are strongly dependent on the size and shape of both guest and solvent molecules, with larger or nonplanar molecules with rigid geometries providing enhanced stability. The greatest observed barrier to guest exchange, ΔG(‡) = 32 ± 0.7 kcal mol(-1) for encapsulated CCl(4) → encapsulated pyrene, is, to the best of our knowledge, indicative of the most powerful kinetic trap ever observed for a synthetic, hydrogen-bonded encapsulation complex. Detailed NMR studies of the structures of the assemblies and the kinetics and mechanisms for guest exchange reveal that subtle differences in guest and solvent structure can impart profound effects on the behavior of the systems. Kinetic and thermodynamic stability, capsule symmetry and structure, guest tumbling rates, susceptibility to disruption by polar solvents, and even the mechanism for equilibration-the presence or absence of supramolecular intermediates-are all greatly influenced. The strongest observed kinetic traps provide encapsulation complexes that are not at equilibrium but are nonetheless indefinitely persistent at ambient temperatures, a property that invites future applications of supramolecular chemistry in open systems where equilibrium is not possible.

Facile Synthesis of Dendritic Hydroxyl‐terminated Cyanuric Chloride Derivatives and Their Properties

AbstractNovel dendritic compounds G1.5(OH)4 and G1.5(OH)8 with peripheral hydroxyl were synthesized under mild conditions from cyanuric chloride, ethylene diamine, ethanolamine and diethanolamine. The products could be separated and purified through dispersion and precipitation in organic solvents with good yields (over 93.0%) and high purity (above 98.0%, HPLC). The structures of the products were characterized by IR, MS, 1 H NMR and elementary analysis. G1.5(OH)4 and G1.5(OH)8 could be dissolved in polar solvents such as methanol, water and dimethylsulfoxide. TGA analysis showed that G1.5(OH)4 and G1.5(OH)8 had good thermo stability. The aqueous solutions of G1.5(OH)4 and G1.5(OH)8 exhibited low surface tension.