Multifunctional Carboxylic Acids Research Articles

Advancements in polyurethane coating: Synthesis and characterization of a novel hyper branched polyester polyol

Hyperbranched polyester polyols have emerged as a promising candidate for polyurethane coatings due to their unique structure and properties. In this context, this paper aims to synthesize a new hyperbranched polyester polyol and evaluate its potential as a polyol for polyurethane coating applications. In this study, the synthesis of hyperbranched polyester polyol involves the reaction between a multifunctional alcohol and a multifunctional carboxylic acid or anhydride. It is further modified by incorporating 2-hydroxyethyl methacrylate and styrene. The properties of the polyester polyol were characterized using various analytical techniques, including FTIR, NMR, SEM and TGA. This paper also provides a discussion on the potential applications of the synthesized hyperbranched polyester polyol in several industries such as automotive, aerospace and construction.

Oxidation of Phenolic Aldehydes by Ozone and Hydroxyl Radicals at the Air-Water Interface.

Biomass burning releases highly reactive methoxyphenols into the atmosphere, which can undergo heterogeneous oxidation and act as precursors for secondary organic aerosol (SOA) formation. Understanding the reactivity of such methoxyphenols at the air-water interface is a matter of major atmospheric interest. Online electrospray ionization mass spectrometry (OESI-MS) is used here to study the oxidation of two methoxyphenols among three phenolic aldehydes, 4-hydroxybenzaldehyde, vanillin, and syringaldehyde, on the surface of water. The OESI-MS results together with cyclic voltammetry measurements at variable pH are integrated into a mechanism describing the heterogeneous oxidative processing of methoxyphenols by gaseous ozone (O3) and hydroxyl radicals (HO•). For a low molar ratio of O3 ≤ 66 ppbv, the OESI-MS spectra show that the oxidation is dominated by in situ produced HO• and results in the production of polyhydroxymethoxyphenols. When the level of O3 increases (i.e., ≥78 times), the ion count of polyhydroxymethoxyphenols increases, while new ring fragmentation products are generated, including conjugated aldehydes and double bonds as well as additional carboxylic acid groups. The interfacial reactivity of methoxyphenols with O3 and HO• is enhanced as the number of methoxy (-OCH3) groups increases (4-hydroxybenzaldehyde < vanillin < syringaldehyde). The experimental observations are summarized in two reaction pathways, leading to the formation of (1) hydroxylated methoxyphenols and (2) multifunctional carboxylic acids from fragmentation of the aromatic ring. The new highly oxygenated products with low volatility are excellent precursors for aqueous SOA formation.

Wood Surface Modification—Classic and Modern Approaches in Wood Chemical Treatment by Esterification Reactions

Wood surface modification is a comprehensive concept which, in time, turned out to be as successful as challenging when it comes to improve the resistance of wood during its life cycle in both indoor and outdoor applications. The initial approaches have aimed at simple methods with immediate results. Nowadays, the paradigm has slightly changed due to the scientific and technical advances, and some methods has become intermediate stages in more complex processes, after being used, for long time, as stand-alone procedures. The esterification was employed as a convenient method for wood surface modification due to the high amount of free hydroxyl groups available at the surface of wood and other lignocellulosic materials. Therefore, different esterification approaches were tested: activated condensation with carboxylic acids (monocarboxylic, as well as dicarboxylic acids, fatty acids, etc.) in the presence of condensation activating agents (such as trifluoroacetic anhydride); reaction with β-halogen-substituted carboxylic acids; esterification using carboxylic acids derivatives (acyl chlorides, anhydrides) or even multifunctional carboxylic acids (i.e., tricine). Thus, wood with improved dimensional stability and weathering resilience, higher fire resistance, enhanced hydrophobic character, and mechanical durability was obtained. This paper offers an overview of some of the most recent advances reported in the field, presented in a systematic manner, using the type of reaction as classification criterion. The main improvements will be outlined in a critical assessment in order to provide an useful tool for a wise choice in future applications.

Cascade aza-Michael Addition-Cyclizations; Toward Renewable and Multifunctional Carboxylic Acids for Melt-Polycondensation.

Although the aza-Michael addition reaction on various unsaturated (di-)carboxylic acids and esters of, for example, itaconic acid, is well-known, the consecutive cyclization reaction has not received much attention in literature. The products of this aza-Michael cascade reaction, being mono- or di-carboxylic acid or ester functionalized N-alkyl-pyrrolidone structures, prove interesting for melt-polycondensation reactions as they exhibit excellent stability at elevated temperatures. In other words, this reaction is a toolbox for the generation of renewable monomers and, in turn, polymers with tunable physiological properties. Therefore, this work provides an overview of the state-of-the-art of the cascade aza-Michael addition-cyclization reactions on biobased unsaturated acids and esters, and their use in polymerization reactions. Furthermore, we extend this overview with the cascade aza-Michael addition-cyclization reaction of trans-trimethyl aconitate with di-amines to form a tetra-functional N-alkyl-bis-(pyrrolidone dimethylcarboxylate), which exhibits excellent thermal stability and could effectively be used as monomer in polycondensation reactions. Importantly, the aza-Michael addition reaction between primary amines and trans-trimethyl aconitate can be considered a click-reaction; it proceeds quantitatively within minutes under ambient conditions and follows the principles of green chemistry.

Multi-functional carboxylic acids for chitosan scaffold

In general, CS scaffold is prepared by lyophilizing CS hydrogel which traditionally can be prepared by dissolving CS in acetic acid and crosslinking with dialdehyde. However, this method expresses unpleasant odor and toxicity leading to obstruct the practical applications. Here, the aqueous solution of multi-functional carboxylic acids is considered as the alternative and ordorless solvents to provide dual functions, i.e. (i) protonation of CS for the dissolution, and (ii) providing the preferable structure to give crosslink networks under amide bond through the conjugation reaction. The present work demonstrates the potential use of multi-functional carboxylic acids for preparation of CS scaffold and shows the tunable physicochemical and mechanical properties. The work also extends to the basic studies on biological properties to propose as the potential material for dental tissue engineering.

Multifunctional Aromatic Carboxylic Acids as Versatile Building Blocks for Hydrothermal Design of Coordination Polymers

Selected recent examples of coordination polymers (CPs) or metal-organic frameworks (MOFs) constructed from different multifunctional carboxylic acids with phenyl-pyridine or biphenyl cores have been discussed. Despite being still little explored in crystal engineering research, such types of semi-rigid, thermally stable, multifunctional and versatile carboxylic acid building blocks have become very promising toward the hydrothermal synthesis of metal-organic architectures possessing distinct structural features, topologies, and functional properties. Thus, the main aim of this mini-review has been to motivate further research toward the synthesis and application of coordination polymers assembled from polycarboxylic acids with phenyl-pyridine or biphenyl cores. The importance of different reaction parameters and hydrothermal conditions on the generation and structural types of CPs or MOFs has also been highlighted. The influence of the type of main di- or tricarboxylate ligand, nature of metal node, stoichiometry and molar ratio of reagents, temperature, and presence of auxiliary ligands or templates has been showcased. Selected examples of highly porous or luminescent CPs, compounds with unusual magnetic properties, and frameworks for selective sensing applications have been described.

Naturally Occurring Acids as Cross-Linkers To Yield VOC-Free, High-Performance, Fully Bio-Based, Degradable Thermosets

Naturally occurring carboxylic acids when used as cross-linkers with a highly functional bio-based epoxy resin result in thermosets having excellent physical and mechanical properties which are also degradable. Thermosets have many important applications (coatings, composites, adhesives, etc.), but they are typically made of nondegradable, nonrenewable materials. In this paper, di- and multifunctional carboxylic acids found in fruit juices as well as other naturally available dicarboxylic acids were used to cross-link epoxidized sucrose soyate (ESS) without the use of extra catalyst or toxic compounds except for water. For the sake of understanding the mechanism of the water-assisted curing reaction between ESS and the acids, the reactivity of the natural acids toward ESS and the curing process were investigated. Water enabled the natural acids with high water solubility and acidity to be dispersed well in ESS and led to rapid cross-linking with ESS. The thermosets possessed excellent thermal and mechanic...

A comparative chemisorption study of acrylic, vinyl acetic, fumaric, maleic and tartaric acid on Si(1 0 0)2 × 1 by van der Waals corrected DFT

The comparative chemisorption of multifunctional carboxylic acids on Si(100)2×1 has been investigated by van der Waals corrected DFT. Several configurations with one or more functional groups involved in the binding process were considered for acrylic, vinyl acetic, maleic, fumaric and tartaric acid both in meso and in chiral form. In general, the dissociative adsorptions are more favourable than the molecular ones. The comparison between uni- and bidentate configurations indicates that the latter is the more favourable for all except for vinyl acetic acid, for which the unidentate on top adsorption is preferred. CC [2+2] cycloadditions are less stable when a second carboxylic group is present and in general are less favourable than SiO linkages. Adsorption through hydroxyl groups is on average slightly less stable than through carboxylic groups. The most stable configuration is obtained with the adsorption through two groups bridging two dimers along a line, by meso tartaric and maleic acid. The simultaneous binding through three functional groups decrease the adsorption energy, whereas the linkage through four functional groups makes the adsorbate unstable. Molecular adsorption such as CO [2+2] cycloadditions and hydroxyl dative bonds have small adsorption energies.

Dielectric properties of supramolecular ionic structures obtained from multifunctional carboxylic acids and amines

Dielectric properties of ionic networks formed from the supramolecular assembly of amine and carboxy functionalised polymers were measured and analyzed.

Use of Multifunctional Carboxylic Acids and Hydrogen Peroxide To Improve Surface Quality and Minimize Phosphine Evolution During Chemical Mechanical Polishing of Indium Phosphide Surfaces

During the chemical mechanical polishing (CMP) of an indium phosphide buffer layer for the fabrication of InGaAs n-channels in CMOS devices, there is interest in controlled removal of In and P atoms from the surface and avoidance of the generation of toxic phosphine (PH3) gas. We report InP removal rates and phosphine generation during InP CMP in hydrogen peroxide based silica particle dispersions in the presence and absence of three different multifunctional chelating carboxylic acids, namely oxalic acid, tartaric acid, and citric acid. The presence of these acids in the polishing slurry resulted in highly smooth surfaces (about 0.1 nm RMS surface roughness) with good InP removal rates (about 400 nm min–1) and very low phosphine generation (<15 ppb). The optimized slurry compositions are reported herein. We use chemical dissolution measurements, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and zeta potential measurements to discuss the InP removal rate and phosphine generation data and to propose InP removal and phosphine generation mechanisms. Thermodynamic calculations of the Gibbs free energy of reaction are used to validate the proposed reactions.

A Versatile Aqueous Reduction of Bio-Based Carboxylic Acids using Syngas as a Hydrogen Source

Syngas as a versatile hydrogen source: Using readily available and economically favorable syngas as a convenient hydrogen source, an efficient and sustainable aqueous reduction of bio-based carboxylic acids has been achieved over a highly robust catalyst system consisting of gold nanoparticles supported on acid-tolerant single-phase monoclinic zirconia (Au/m-ZrO(2)). A range of bio-based multifunctional carboxylic acids have been selectively converted into their corresponding lactones or diols in high to excellent yields.

One Pot Synthesis of Multifunctional Aramid Aerogels

ABSTRACTAerogels are quasi-stable, low-density, three-dimensional assemblies of nanoparticles, but they are commonly associated with poor mechanical properties. The most successful efforts to improve their mechanical properties involve cross-linking of the skeletal nanoparticles with polymers. However, post gelation cross-linking is time-consuming. Hence, it is reasonable to seek robust all-polymer aerogels among polymers known for their high mechanical strength. As a result, here we report the facile one-pot synthesis of a new class of Kevlar-like aerogels based on the rather underutilized reaction of multifunctional isocyanates and carboxylic acids. The resulting materials are up to 84% v/v porous with surface areas as high as 380 m2 g-1. The ultimate compressive strength per unit density is within 10% equal to that of Kevlar 49. The high specific energy absorption (37 J g-1) and Styrofoam-like thermal conductivity (0.028 W m-1 K-1) combined with thermal stability up to 350 °C render aramid aerogels multifunctional materials suitable for defense, civil and transportation related applications. Upon pyrolysis at 800 °C they can be converted to 80% (v/v) porous, electrically conducting carbons with surface areas as high as 474 m2 g-1.

Cross-Linking Cotton Cellulose by the Combination of Maleic Acid and Sodium Hypophosphite. 2. Fabric Fire Performance

Multifunctional carboxylic acids have been used as durable press finishing agents for cotton with sodium hypophosphite (NaH2PO2) as the most effective catalyst. In our previous research, we found that cellulose cross-linking takes place when cotton fabric treated with a combination of maleic acid and NaH2PO2 is cured at ≥150 °C. The data suggested that H−P−H of hypophosphite likely reacts with >C═C< of the maleic acid already esterified with cotton cellulose, thus making it possible to form cross-linking on cotton. In this research, we studied the effect of the maleic acid (MA) and NaH2PO2 treatment on the fire performance of cotton using microscale combustion calorimetry. We found that esterification of cotton by MA reduces the flammability of the cotton cellulose. NaH2PO2 catalyzes the esterification of MA on cotton, thus further reducing the cotton fabric’s flammability by increasing esterification on cotton. The quantity of ester formed on cotton reaches the optimum range when the curing temperature i...

Towards closing the gap between hygroscopic growth and CCN activation for secondary organic aerosols – Part 3: Influence of the chemical composition on the hygroscopic properties and volatile fractions of aerosols

Abstract. The influence of varying levels of water mixing ratio, r, during the formation of secondary organic aerosol (SOA) from the ozonolysis of α-pinene on the SOA hygroscopicity and volatility was investigated. The reaction proceeded and aerosols were generated in a mixing chamber and the hygroscopic characteristics of the SOA were determined with the Leipzig Aerosol Cloud Interaction Simulator (LACIS) and a Cloud Condensation Nuclei counter (CCNc). In parallel, a High-Resolution Time-of-Flight Aerodyne Aerosol Mass Spectrometer (HR-ToF-AMS) located downstream of a thermodenuder (TD) sampling from the mixing chamber, to collect mass spectra of particles from the volatile and less-volatile fractions of the SOA. Results showed that both hygroscopic growth and the volatile fraction of the SOA increased with increases in r inside the mixing chamber during SOA generation. An effective density of 1.40 g cm−3 was observed for the generated SOA when the reaction proceeded with r&gt;1 g kg−1. Changes in the concentrations of the fragment CO2+ and the sum of CxHyOz+ (short name CHO) and CxHy+ (short name CH) fragments as measured by the HR-ToF-AMS were used to estimate changes in the oxidation level of the SOA with reaction conditions, using the ratios CO2+ to CH and CHO to CH. Under humid conditions, both ratios increased, corresponding to the presence of more oxygenated functional groups (i.e., multifunctional carboxylic acids). This result is consistent with the α-pinene ozonolysis mechanisms which suggest that water interacts with the stabilized Criegee intermediate. The volatility and the hygroscopicity results show that SOA generation via ozonolysis of α-pinene in the presence of water vapour (r&lt;16.9 g kg−1) leads to the formation of more highly oxygenated compounds that are more hygroscopic and more volatile than compounds formed under dry conditions.

Flame retardant finishing of cotton fleece: part VII. Polycarboxylic acids with different numbers of functional group

In our previous research, multifunctional carboxylic acids have been used as flame retardants to reduce the flammability of cotton fleece so that the garment made of cotton fleece can pass the US mandatory requirement specified by the government regulation “Standard for the Flammability of Clothing Textiles” (16 CFR 1610). In this research, we studied and compared the effectiveness of the polycarboxylic acids having different numbers of carboxylic groups as the durable flame retardants for cotton fleece. The cotton fabrics were treated with 1,2,3,4-butanetetracarboxylic acid (BTCA), citric acid (CA), succinic acid (SUA) and malic acid (MLA). We compared the reactivity of those polycarboxylic acids to esterify cotton cellulose and their effectiveness to reduce the flammability of the cotton fleece. The data indicated that the polycarboxylic acids with higher functionalities (BTCA and CA) form more esterlinkages on cotton and are more durable to home launderings than that treated with their bifunctional counter parts (SUA and MLA, respectively). In addition, the cotton fabrics treated with BTCA and CA have higher dimensional stability and higher strength loss. All those differences can be attributed to the fact that only those acids with three or more carboxylic groups, i.e., BTCA and CA, are able to crosslink cotton cellulose whereas the bifunctional acids (SUA and MLA) only form single esterlinkage with cotton.

Calorimetric measurements of proton adsorption onto Pseudomonas putida

Having an understanding of the reactive nature of the bacterial surface is enhanced when its reactivity is considered in a thermodynamic framework. Towards this end, isothermal titration calorimetry was used to measure heats of proton adsorption onto Pseudomonas putida, a common Gram negative soil bacterium. Proton adsorption generated large exothermic heats and proton uptake continued down to pH 2.5. Applying a surface complexation model to the calorimetric data allowed for the derivation of site-specific enthalpies and entropies of proton adsorption. The 4-site non-electrostatic model of Borrok et al. [D.M. Borrok, J.B. Fein, J. Colloid Interface Sci. 286 (2005) 110] was chosen to describe proton adsorption and enabled derivation of site-specific enthalpies of −2.4 ± 0.3, −3.7 ± 0.2, −9.0 ± 0.6, and −36.0 ± 1.2 kJ/mol for Sites 1–4, respectively. Entropies of proton adsorption were calculated to be 51 ± 3, 75 ± 1, 91 ± 2, and 55 ± 4 J/mol K, for Sites 1–4, respectively. Enthalpies and entropies of Sites 1 and 3 are consistent with that of multifunctional organophosphonic acids, Site 2 is consistent with multifunctional carboxylic acids, and Site 4 is consistent with an amine. Temperature dependence of the acidity constants for Sites 1–3 is predicted to be minimal; however, Site 4 is predicted to more substantially affected by temperature.

Interfacial polymerization of an epoxy resin and carboxylic acids for the synthesis of microcapsules

AbstractBACKGROUND: Microencapsulation technology promises new applications such as intelligent microstructures, phase change materials and self‐healing composites. Microcapsule synthesis and characterization have been researched extensively; however, the well‐known polymerization between epoxy resins and carboxylic acids has not been used to prepare microcapsules.RESULTS: Microcapsules were prepared by interfacial polymerization of an oil‐in‐water emulsion which contained a commercial epoxy resin and multifunctional carboxylic acids. The microcapsules obtained were characterized using optical microscopy and scanning electron microscopy. Experiments performed at lower stirring rates led to larger microcapsules, in the range 100–400 µm, while higher stirring rates resulted in microcapsules in the range 10–50 µm.CONCLUSIONS: Microcapsules can be prepared by interfacial polymerization of epoxy resins, an extensively studied and widely used class of polymers. By means of NMR characterization we gained insight into the mechanism of polymerization at the interface wherein products coming from the more hindered ring opening as well as from intermolecular transesterification are identified. The presence of a crosslinker affects the morphology of the external microcapsule surface. Copyright © 2008 Society of Chemical Industry

Implantable photonic crystal for reflection-based optical sensing of biodegradation

Biodegradable inverse opal (IoPPC) was synthesized from a multifunctional carboxylic acid and polyols by colloidal crystal templating. The IoPPC was prepared by infiltration of the monomer solution into interparticle voids of silica colloidal crystal template, polycondensation of the infiltrated film, and removal of the template. The synthesized IoPPC was characterized by infrared absorption, X-ray diffraction measurements, differential scanning calorimetry, and thermogravimetry/mass spectrometry analysis. In order to clarify the effect of biodegradation on the inverse opal structure and the optical reflection property, the IoPPC was implanted in subcutaneous tissue of the lower back of three mice (ICR, 10 weeks, female). After the 2 weeks implantation, fragmented samples were harvested from the implant location and investigated by scanning electron microscope observations and optical reflection measurements. It was found that the reflection peak for the harvested samples decayed from that for the sample without implantation. Such a spectral change is considered to be attributed to the deterioration of the regularity of the inverse opal structures through biodegradation. The finding of this study will serve in the development of reflection-based sensing in various biomedical applications.

Nonformaldehyde Flame Retardant Finishing of the Nomex/Cotton Blend Fabric Using a Hydroxy-Functional Organophosphorus Oligomer

Multifunctional carboxylic acids, such as 1,2,3,4-butanetetracarboxylic acid (BTCA), have been used as durable press finishing agents to produce wrinkle-resistant cotton. In our previous research, we used BTCA as a nonformaldehyde bonding agent in the flame retardant finishing system based on a hydroxy-functional organophosphorus oligomer (HFPO) for cotton. In this research, we investigate the application of HFPO to the 65%/35% Nomex/cotton blend fabric using BTCA as a bonding agent and triethanolamine (TEA) as a co-reactant. We found that the addition of TEA in the flame retardant finishing system improves the hydrolysis resistance of the HFPO bound to the Nomex/ cotton blend and enhances the flame retardant performance of HFPO by means of phosphorus—nitrogen synergism. Moreover, TEA reduces the deposit of calcium salt on the treated fabric during laundering by esterifying the free carboxylic acid groups on cotton. The Nomex/cotton blend fabric treated with the HFPO/BTCA/TEA system shows high flame retardant performance at relatively low add-on levels. It is a completely nonformaldehyde flame retardant finishing system.

Morphology assessment of chemically modified cryostructured poly(vinyl alcohol) hydrogel

The morphology of hydrogels based on poly(vinyl alcohol) (PVA) in their frozen hydrated state, modified with biologically active di- and multifunctional molecules was studied by scanning electron microscopy (SEM) with cryo-attachment. The porosity of samples was found to be more regular and ordered in the case of samples containing difunctional, and especially multifunctional carboxylic acids as compared to the neat PVA hydrogel. The morphology is dependent not only from the hydrogel composition but also the number of freezing–thawing cycles. Resulted highly porous and oriented structure has significant influence on materials properties, such as compressive stress and crosslinking density.