Content Of Hydroxy Groups Research Articles

Bio-oil Fractionation According to Polarity and Molecular Size: Characterization and Application as Antioxidants.

Bio-oil obtained from biomass pyrolysis has great potential for several applications after being upgraded and refined. This study established a method for separating bio-oil into different fractions based on polarity and molecular size to extract phenolic and polyphenolic compounds with antioxidant properties. The fractions were analyzed using various spectroscopic and chromatographic techniques, such as GC/MS, FTIR, UV-vis, SEC, DOSY-NMR, 13C-NMR, and 31P-NMR. The antioxidant properties of these fractions were tested by examining their ability to improve the oxidative stability of biodiesel. The results strongly connected the bio-oil's chemical functionalities and antioxidant power. During solvent fractionation, dichloromethane could extract phenolic structures, which were subsequently size-fractionated. The subfractions with lower molecular weight (in the order of monomers and dimers) outperformed the antioxidant potential of the crude bio-oil. Heavier subfractions from dichloromethane extraction did not show good antioxidant abilities, which was related to the low hydroxy group content. After solvent extraction, phenolic oligomers remained in the water-insoluble/dichloromethane-insoluble fraction, which showed good antioxidant potential despite its low solubility in biodiesel.

A BN Aromatic Ring Strategy for Tunable Hydroxy Content in Polystyrene.

BN 2-vinylnaphthalene, a BN aromatic vinyl monomer, is copolymerized with styrene under free radical conditions. Oxidation yields styrene-vinyl alcohol (SVA) statistical copolymers with tunable hydroxy group content. Comprehensive spectroscopic investigation provides proof of structure. Physical properties that vary systematically with hydroxy content include solubility and glass transition temperature. BN aromatic polymers represent a platform for the preparation of diverse functional polymeric architectures via the remarkable reaction chemistry of C-B bonds.

A BN Aromatic Ring Strategy for Tunable Hydroxy Content in Polystyrene

AbstractBN 2‐vinylnaphthalene, a BN aromatic vinyl monomer, is copolymerized with styrene under free radical conditions. Oxidation yields styrene–vinyl alcohol (SVA) statistical copolymers with tunable hydroxy group content. Comprehensive spectroscopic investigation provides proof of structure. Physical properties that vary systematically with hydroxy content include solubility and glass transition temperature. BN aromatic polymers represent a platform for the preparation of diverse functional polymeric architectures via the remarkable reaction chemistry of C−B bonds.

Redox functionalization of carbon electrodes of electrochemical capacitors

It is shown that the liquid oxidative treatment of microporous active carbon (AC) of the Norit DLC Supra 30 grade by nitric acid in the presence of carbamide results in an increase in the content of hydroxy groups on the AC surface at the practically unchanged content of carboxyl groups. Redox functionalization and appearance of pseudocapacity result in an increase in the carbon electrode capacity by 26%. The surface state of the carbon material is characterized using the infrared spectroscopy and Boehm titrimetry techniques, while the electrochemical characteristics are studied using the method of cyclic voltammetry in 3 M sulfuric acid solution. Studies of degradation of the electrodes of the initial and modified active carbons show that capacity decreases by 3 and 8%, accordingly, after 1 thousand charging–discharge cycles.

Decrease in the performance of a phenolic antioxidant in preparation of inhibited polyethylene films by hot pressing

The effect exerted on the efficiency of the polymer inhibition by the conditions (pressure, treatment time, antioxidant concentration) of preparing films of polyethylene with Irganox 1010 phenolic antioxidant by hot pressing was studied. Blends of the antioxidant with the polymer were prepared by treatment of the binder particles with a solution of Irganox 1010 in acetone. After drying to remove the solvent, films were prepared from the dry blends by hot pressing. The films were subjected to oxidation in the molten state in air. Evolution of the characteristic IR absorption bands of the antioxidant and polymer was monitored. The inhibition efficiency was evaluated by the induction period of the film oxidation. Two interrelated processes occur concurrently in the course of hot pressing: sorption uptake of the antioxidant, resulting in its more uniform distribution in the bulk of the sample, and a decrease in the relative content of hydroxy groups, i.e., partial degradation of the inhibitor. The latter process can decrease the efficiency of the polymer inhibition. Therefore, in development of polymer compounds with enhanced oxidation resistance, it is necessary to optimize the process conditions, namely, the composition of the ingredients, the procedure for introducing the antioxidant, and the temperature and time of sample preparation.

Determination of Hydroxy Groups in the Modified Epoxy Oligomers Using IR-Spectroscopy

The use of IR-spectroscopy has been proposed to determine the content of hydroxy groups in the modified functional oligomers based on bisphenol A diglycidyl ether. Apart from hydroxy groups the investigated oligomers contain epoxy or peroxy, carboxy or acrylic groups.

Hydroxyapatite formation on titania-based materials in a solution mimicking body fluid: Effects of manganese and iron addition in anatase.

Hydroxyapatite formation on the surfaces of implanted materials plays an important role in osteoconduction of bone substitutes in bone tissues. Titania hydrogels are known to instigate hydroxyapatite formation in a solution mimicking human blood plasma. To date, the relationship between the surface characteristics of titania and hydroxyapatite formation on its surface remains unclear. In this study, titania powders with varying surface characteristics were prepared by addition of manganese or iron to examine hydroxyapatite formation in a type of simulated body fluid (Kokubo solution). Hydroxyapatite formation was monitored by observation of deposited particles with scale-like morphology on the prepared titania powders. The effect of the titania surface characteristics, i.e., crystal structure, zeta potential, hydroxy group content, and specific surface area, on hydroxyapatite formation was examined. Hydroxyapatite formation was observed on the surface of titania powders that were primarily anatase, and featured a negative zeta potential and low specific surface areas irrespective of the hydroxy group content. High specific surface areas inhibited the formation of hydroxyapatite because calcium and phosphate ions were mostly consumed by adsorption on the titania surface. Thus, these surface characteristics of titania determine its osteoconductivity following exposure to body fluid.

Pseudo-living copolymerization of norbornene and ω-alkenylborane – Synthesis of monodisperse functionalized cycloolefin copolymer

The synthesis of norbornene copolymer with hydroxy groups was performed by the copolymerization of norbornene (NB) with 9-(7-octenyl)-borabicyclo[3.3.1]nonane (OctBBN) using ansa-dimethylsilyl(fluorenyl)(amido)titanium catalyst (1) activated by Ph3CB(C6F5)4 and successive oxidation. The glass transition temperature (Tg) of the copolymer was higher than the polymer with the same hydroxy group content synthesized by the copolymerization of NB and ω-alkenylaluminum. The 13C NMR spectrum of the copolymer clearly showed that alkylborane moiety was converted quantitatively to hydroxy groups. Copolymerization of NB and OctBBN by the 1-MMAO/BHT system proceeded in a pseudo-living manner without chain transfer reaction.

Effect of oxidative treatment on the colloid-chemical properties of lignosulfonates

The effect of oxidative treatment on colloid-chemical properties of lignosulfonates was studied. Oxidation of lignosulfonates (403–423 K, \(P_{O_2 } \) = 0.2–0.8 MPa, 0.5–1 h) is accompanied by a decrease in the content of hydroxy groups and by an increase in the content of carbonyl groups in oxidation products. Under severe oxidation conditions (423–433 K, \(P_{O_2 } \) = 0.8 MPa, 3 h), lignosulfonates undergo chemical degradation with the formation of lower carboxy derivatives. The oxidized lignosulfonates exhibit lower performance, compared to the initial samples, in wetting and dispersion of sphalerite and elemental sulfur.

Interfacial chemistry using a bifunctional coupling agent for enhanced electrical properties of carbon nanotube based composites

A bifunctional coupling agent (BCA) containing one oxazoline and one benzoxazinone group was applied to promote a reaction between polyamide 12 (PA12) and multiwalled carbon nanotubes (MWCNTs) during melt mixing. With this modification, the MWCNT content needed for the electrical percolation was significantly reduced by more than a factor of three. For amino functionalized MWCNT–PA12 composites adding 1 wt.% BCA electrical percolation was reached at only 0.37 wt.% MWCNTs compared to 1.0 wt.% without BCA. With the help of a model reaction, the covalent attachment of the BCA to the MWCNTs could be shown by thermogravimetric analysis (TGA) and via fluorescence spectroscopy. Model compounds were applied containing either only the oxazoline or the benzoxazinone group to show that the better electrical properties in the PA12–MWCNT composites were a result of a covalent bond between the polymer and the nanotube which only takes place when the BCA was used. In addition, significantly higher electrical conductivity values were obtained by the addition of BCA as well with amino functionalized as with nonmodified commercial MWCNTs. This surprising result was attributed to the significant hydroxy group content on the surface of those commercial MWCNTs.

Hepatocytes exhibit constant metabolic activity on carboxymethylcellulose-based hydrogel with high phenolic hydroxy group content

Maintenance of cellular number and functions of attached hepatocytes during culture is an important requirement for hepatocyte-based drug screening applications. In this study, two carboxymethylcellulose (CMC)-based hydrogels were used as hepatocyte culture substrata to improve the stability of cellular adhesiveness, bioactivity and hepatic function of primary rat hepatocytes. The hydrogels were prepared from aqueous solutions of CMCs with 16.7 (CMC-Ph16) and 7.3 (CMC-Ph7) phenolic hydroxy (Ph-OH) groups per 100 repeat units of uronic acid, via peroxidase-catalyzed crosslinking reaction between Ph-OH groups. Hepatocytes formed aggregates on both hydrogels but the aggregates on CMC-Ph16 gel had more flattened configuration than on CMC-Ph7 gel. The flat aggregates stably immobilized onto CMC-Ph16 gel while spherical aggregates on CMC-Ph7 gel could be easily detached from the surface. In addition, hepatocytes on CMC-Ph16 gel showed more stable mitochondrial dehydrogenase activity and albumin secretion function for 7 days than on CMC-Ph7 gel, tissue culture polystyrene (TCPS), and TCPS coated with collagen (CL). The retention of albumin secretion function per well after 7 days of seeding was 86% on CMC-Ph16 gel, 18% on CMC-Ph7 gel, 9% on TCPS, and 6% on CL. These results demonstrate that CMC-Ph16 gel is a good candidate substratum for hepatocyte-based drug testing applications.

Synthesis, characterisation and solution thermal behaviour of a family of poly ( N-isopropyl acrylamide-co- N-hydroxymethyl acrylamide) copolymers

Thermo-responsive copolymers of poly ( N-isopropyl acrylamide-co- N-hydroxymethyl acrylamide)p(NIPAAm-co-HMAAm) with a range of content of hydroxy groups have been synthesised by free radical polymerisation. The polymers were characterised by NMR, FTIR and GPC. A detailed study of the solution thermal properties showed that polymers with up to about 50 wt.% hydroxy monomer show lower critical solution temperature (LCST) properties in water. Polymers with higher hydroxy monomer content are fully soluble at all temperatures up to 100 °C. The effect of pH, salts and solvent additives on the solution thermal behaviour of the copolymers was investigated, showing that “salting-out” salts lowered the LCST and “salting-in” salts caused an initial increase in LCST at low concentrations, but reduced LCST at higher concentrations, in line with the Hoffmeister series. The LCST of any copolymer composition from this family in pure water can be predicted from the empirical equation; LCST = 0.015 x 2 + 0.25 x + 31.76, where x is the fraction of the hydroxy monomer. Due to differences in polarity and the length of the carbon chain, methanol and ethanol altered LCST of p(NIPAAm) and its hydroxyl copolymers in different manners, showing a transition from cononsolvency to cosolvency as the hydroxyl content of the copolymer increased. A more complex polyhydroxy compound, sucrose, had very little effect on LCST for either p(NIPAAm) or its hydroxyl copolymers.

Preparation of polymethylsilsesquioxanes by the base‐catalyzed hydrolytic polycondensation of triisopropoxy(methyl)silane

AbstractBase‐catalyzed hydrolytic polycondensation of trialkoxymethylsilane was investigated to synthesize polymethylsilsesquioxanes (PMSs). The reaction of trimethoxy(methyl)silane and triethoxy(methyl)silane with tetramethylammonium hydroxide, tetrabutylammonium hydroxide, and also coline gave insoluble gels. Polymethylsilsesquioxane (PMS‐IP) was obtained by the reaction of triisopropoxy(methyl)silane (MTIPS) with tetrabutylammonium hydroxide as a catalyst. PMS‐IP was composed primarily of T2 and T3 units. The percentage of T3 units and the molecular weight of PMS‐IP increased with increases in the molar ratios of catalyst and water to MTIPS and with the reaction time. PMS‐IP was soluble in organic solvents, except for methanol, and was separated by extraction with hexane and methanol into low‐ and high‐molecular‐weight fractions of Mw 2800–4000 and 7300–88,300, respectively. PMS‐IP coating films were prepared by dip coating on the organic, inorganic, and metal substrates, using the acetone–isopropyl alcohol solution of PMS‐IP. Since PMS‐IP solutions prepared with tetrabutylammonium hydroxide were hardly used because of the low content of hydroxy groups in the polymer, they showed low adhesion when compared with those solutions prepared with hydrochloric acid. The dielectric constant of the coating film prepared from the high‐molecular‐weight PMS‐IP was 2.6. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3623–3630, 2005

Fluorescence enhancement and structural development of sol–gel derived Er3+-doped SiO2 by yttrium codoping

Er3+–Y3+ codoped SiO2 powdered bulks were prepared by a sol–gel process. The effect of Y3+ codoping on the fluorescence properties and structural development of Er3+-doped SiO2 is investigated. The maximum ∼1.54 µm photoluminescence (PL) intensity occurs in the sample with Er3+ (10 mol%)–Y3+ (50 mol%) codoped and annealed at 985 °C. This can be attributed to the competition between the content of hydroxy groups and Er site symmetry. Improvement of optimum PL properties due to Y3+ codoping by a factor of ∼20 for intensity and 1.8 for the full width at half maximum (57 nm) was obtained in comparison with the Er3+-doped SiO2 system. Extended X-ray absorption fine structure analysis shows that the local chemical environment of Er3+ ions in the Er3+–Y3+ codoped SiO2 is similar to that in Er2O3. The average spatial distance between Er3+ ions is enlarged due to a partial substitution of Y3+ for Er3+ ions in the Er2O3-like local structure, which results in a reduction of the concentration quenching effect.

Chemical features and seasonal variation of fine aerosol water-soluble organic compounds in the Po Valley, Italy

We present here an investigation on the annual cycle of the carbonaceous fraction of the Po Valley (Italy) fine ( d<1.5 μm) aerosol. Water-soluble organic compounds (WSOC) characterisation was accomplished using a simplified procedure, described in the paper, of a previously proposed methodology. The new simplified procedure allows the analysis of large sets of samples, which was difficult to achieve with the previous complex and labour-intensive method. The results of this study show that the aerosol total carbon (TC) concentration follows the same annual trend as the aerosol inorganic ion constituents, characterised by lower concentration values during the summer and higher concentrations in winter. The total aerosol organic carbon (OC) represents from 90 to 97% of TC, the rest being accounted for by elemental carbon. Within this study, we studied in particular the aerosol WSOC, a class of chemical compounds for which present knowledge is rather limited. In our samples, WSOC account for between 38% (in winter) and 50% (in summer) of OC, in terms of carbon. WSOC were fractionated into three main classes: (a) neutral/basic compounds; (b) mono- and di-carboxylic acids; (c) polyacidic compounds. The three fractions together accounted for an average 87% of total aerosol WSOC. The acidic compounds (mono- and di-carboxylic acids+polyacidic compounds) were found to be far more abundant than the neutral ones in all seasons, with polycarboxylic acids being the most abundant class of WSOC in spring, fall, and winter, while the mono/di-acids are dominant in summer. The main structural features of aerosol WSOC, revealed by proton nuclear magnetic resonance, suggest that WSOC are composed of highly oxidised species with residual aromatic nuclei and aliphatic chains. In particular, neutral compounds are mainly polyols or polyethers, mono/di-acids are mainly hydroxylated aliphatic acidic compounds, and polyacids are highly unsaturated compounds of predominantly aliphatic character, with a minor content of hydroxy groups.

Dextran as antioxidant's activity carrier

AbstractTwo series of conjugates of dextran and antioxidants from the class of sterically hindered phenols were prepared. The conjugates were characterized by the substitution degree of glycoside units, solubility in different solvents, intrinsic viscosity. The investigation of radical scavenging activity (RSA) of conjugates was carried out in their reactions with two free radicals — 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and sodium salt of 2,2‐diphenyl‐1‐picrylhydrazyl sulfonic acid (DPPH‐salt). The usage of water soluble DPPH‐salt enabled to estimate the RSA of the conjugates in water. It was shown that the rate constants of interaction of the DPPH‐salt and the conjugates were 10–30 times higher than this value for low‐molecular analogue of phenoxan. High RSA of the conjugates in water can be explained by large solvation shell formed due to high content of hydroxy groups in dextran.

Acylation of acetylcellulose with pyromellitic dianhydride

The cross-linking reactions of acetylcelluloses having different levels of acetyl groups with pyromellitic dianhydride in homogeneous media have been investigated. A relationship has been established between the static exchange capacity (SEC) and the content of hydroxy groups in the acetylcellulose and the exterification conditions (homogeneous or heterogeneous-solid phase). It has been shown that on the interaction of acetylcellulose with pyromellitic dianhydride under homogenous conditions there is a uniform distribution of cross-linkages over the whole length of the acetylcellulose macromolecule, which enables products with high SEC values to be obtained.

Determination of the content of hydroxy groups in cottonseed oil

IR spectroscopy has been used to determine the content of hydroxy groups in cottonseed oil in relation to the periods of ripening. It has been found that the largest amount of hydroxy groups is present in the oil of the early stages of ripeness.

Monolayer studies of some ethoxylin resin adhesives and related compounds

AbstractCompression isotherms of monolayers of ethoxylin resins and related compounds have been studied at the air–water interface, and the orientation of such monolayers at the interface has been described. The monolayer thickness has been measured by the multilayer technique. It has been shown that resin‐substrate adhesion is strongly dependent on the hydroxy group content of the resin, and is independent of the epoxy group content, the molecular weight, and the hydrocarbon group content of the resin. Furthermore, it has been shown that the presence of epoxy groups results in high intermolecular cohesion of the prehardened resin; this, in turn, will tend to minimize resin shrinkage during the hardening process and thus improve the joint strength.