Hydrogen Atom Of Hydroxyl Group Research Articles

Improvements of the increase of selenium-modified rate on the structural characteristics and antioxidant properties of Lycium barbarum polysaccharides by subcritical water method

Effects of the increase of the selenium-modified rate on the structural characteristics and antioxidant abilities of the selenized polysaccharides (Se-PS) were seldom reported. In this work, LBP1-1 purified from Lycium barbarum polysaccharides (LBP) was selenized by the subcritical water (SW) versus the traditional hot water (HW) method to obtain Se-modified SW-SeLBP1-1 and HW-SeLBP1-1, respectively. The results revealed that SW-SeLBP1-1 contained 17.49 ± 0.35 mg Se/g, significantly higher than 5.68 ± 0.05 mg/g of HW-Se-LBP1-1 and the reported before. The selenization time was reduced from 7 h to 20 min. Se modifications were mainly achieved by Se substitutions of hydrogen atoms in hydroxyl groups of LBP1-1. Xylose and galactose in LBP1-1 could be easily and regularly modified by Se, the Se modifications of the other monosaccharides showed significant different between the two methods. The generated C-O-Se groups could readily make SW-SeLBP1-1 formed a more orderly network structure than that of HW-SeLBP1-1 when Se-modified rate increased 11.81 %, resulting in its antioxidant activities increasing over 17.3 % in vitro.

Unraveling the structural and dynamic heterogeneities of hydroxyl-functionalized di-cationic ionic liquids (HFDILs): An integrated ab initio and molecular dynamics approach

This study comprehensively investigates the effects of hydroxyl groups in side chains and cation symmetry on intra- and inter-molecular structures, dynamics, and thermodynamic properties of two hydroxyl-functionalized di-cationic ionic liquids (HFDILs). Using a combination of molecular dynamics (MD) simulations and quantum chemistry (QC) calculations, we compare the influence of these effects on various properties with corresponding non-hydroxyl DILs reported in previous works. The structure of HFDILs is explored using angle distribution, radial distribution, spatial distribution, and combined distribution functions. Also, the averaged noncovalent interaction (aNCI) analysis is used to characterize the weak noncovalent interactions in fluctuating environment of HFDILs. Results showed that the oxygen atoms of anion have the strongest interaction with the hydrogen atom of hydroxyl group, followed by the hydrogen atom at the top of the imidazolium ring. Domain analysis and Voronoi calculations are performed to investigate the number of polar and non-polar subunits, revealing that symmetric HFDILs with two hydroxyl groups in their side chains have greater structural heterogeneity than asymmetric ones with only one hydroxyl group due to the larger accumulation of non-polar subunits. To investigate dynamical heterogeneity, we calculate the non-Gaussian parameter, van Hove correlation, hydrogen bond, ion pair, ion cage, and reorientation dynamics. Results indicated that symmetric HFDILs have slower dynamics, greater dynamic heterogeneity, and more stability than asymmetric ones. Finally, the structure and strength of ion triplet interactions are examined using quantum mechanical methods, revealing that symmetric HFDILs are more stable than asymmetric ones. This study provides valuable information for understanding DILs and their potential applications in various fields.

QM/MM study of N501 involved intermolecular interaction between SARS-CoV-2 receptor binding domain and antibody of human origin

Intermolecular interaction between key residue N501 of the epitope on SARS-CoV-2 RBD and screening antibody B38 was studied using the QM/MM and QM approach. The QM/MM optimized geometry shows that angle X-H---Y is 165° for O-H---O between mAb light chain S30 and RBD N501. High level MP2 calculations indicated the interaction between RBD N501 and S30 of B38 Fab light chain provide a relatively strong attractive force of − 3.32 kcal/mol, whereas the hydrogen bond between RBD Q498 and S30 was quantified as 0.10 kcal/mol. The decrease in ESP partial charge on hydrogen atom of hydroxyl group on S30 drops from 0.38 a.u. to 0.31 a.u., exhibiting the sharing of 0.07 a.u. from the lone pair electron oxygen of N501 due to hydrogen bond formation. The NBO occupancy of hydrogen atom also decreases from 25.79 % to 22.93 % in the hydroxyl H-O NBO bond of S30. However, the minor change of NBO hybridization of hydroxyl oxygen of S30 from sp3.00 to sp3.05 implies the rigidity of hydrogen bond tetrahedral geometry in the relative dynamic protein complex. The O-H---O angle is 165° which is close but not exactly linear. The structural requirement for sp3 hybridization of oxygen for hydroxyl group on S30 and dimension of protein likely prevent O-H---O from adopting linear geometry. The hydrogen bond strengths were also calculated using a variety of DFT methods, and the result of − 3.33 kcal/mol from the M06L method is the closest to that of the MP2 calculation. Results of this work may aid in the COVID-19 vaccine and drug screening.

Analysis of Adhesion at the Interface of Steamed Bread and Eggshell

The adhesion phenomenon of polymers occurs in nature and in human activity. In the present paper, an adhesion system of steamed bread and eggshell was observed in formation when steamed bread and eggshells were placed in close contact and cooled slightly in the ambient air. The adhesion phenomena and mechanism of the adhesion interface between the steamed bread and eggshell were investigated and systematically discussed. Strong-bond interfaces were observed by scanning electron microscope (SEM). The formation process and mechanism of the strong-bond adhesion were also analyzed molecular dynamics simulation technology, and the results are discussed. The simulation analyses showed that the starch molecules at the calcite (104) crystal face were diffused in a water vapor environment, and the formation and solidification of multiple hydrogen bonds in the starch chain and oxygen atoms in the calcium carbonate were observed in detail during cooling. The diffusion rate of hydrogen atoms in hydroxyl groups on the calcite surface decreased gradually with the decrease of the cooling temperature of the steamed bread's upper surface. The strong adhesion of the steamed bread and eggshell is attributed to the synthetic effect of the absorption, diffusion, surface chemistry, and the formation of multiple hydrogen bonds between the starch from the steamed bread and the calcium carbonate crystals in eggshell. The interesting findings are helpful for the design of strong bonds, and provide an idea for new environmentally friendly adhesive materials.

How are Hydroxyl Groups Localized on a Graphene Sheet?

Arrangements of hydroxyl groups on graphene sheets were systematically investigated using density functional theory calculations that included van der Waals interactions. Results show that hydroxyl groups tend to gather at para-positions on graphene sheets to generate perfect ring-like hexahydroxyl group adsorption. The close proximity of hydroxyl groups is in good agreement with the experimental separation between unoxidized, aromatic and oxidized, saturated regions in graphene oxide. The orientation of hydrogen atoms in hydroxyl groups creates both O–H···O and O–H···π hydrogen bonds. Calculations also indicated that the binding energy per hydroxyl group follows a logarithmic function with respect to the number of hydroxyl groups. Besides, the opening band gap was observed for several derivatives, and the relationship between the band gap and O/C ratio was found to be nonmonotonic. Analysis of the density of states showed that bands around the Fermi levels of derivatives between graphene and hydroxyl groups are mainly composed of 2pz orbitals of carbon and oxygen atoms.

Theoretical investigation on the structure and physicochemical properties of choline chloride-based deep eutectic solvents

Deep eutectic solvents (DESs) are analogous to ionic liquids that have been widely employed in scientific research and engineering applications. The physicochemical properties of DESs, including the density, viscosity, and nanostructure, serve as the foundation for green solvent development. In the present work, the density and viscosity of choline-based DESs at 293.15–353.15 K were simulated using molecular dynamics (MD) simulation under the Generation Amber Force Field. The radial distribution function (RDF) and number of hydrogen bonds of the selected systems were analysed. It was found that a large amount of the hydrogen bonding network was formulated between chlorine and hydrogen atoms in hydroxyl groups, which greatly decreased the melting temperature of the solvent in comparison with the pure components. The intermolecular interaction decreased with increasing temperature as well as the length of the alkyl chain on the hydrogen bond donor (HBD). Furthermore, an increase in the number of hydroxyl groups in HBD molecules leads to the formation of a more complex and extensive hydrogen bond network, which results in a higher viscosity of the DES.

Silk sericin as a bio-initiator for grafting from synthesis of polylactide via ring-opening polymerization

In this study, a new graft copolymer (SS-g-PLA) was constructed by combining sericin and polylactide (PLA) via ring-opening polymerization (ROP) having Sn(Oct)2 as a catalyst. In this synthetic strategy based on the grafting from concept, sericin molecule acts as a bio-initiator where its hydroxyl groups existing in serine units. The effects of polymerization parameters, including reaction temperature, the concentration of catalyst and sericin, on the copolymer structure and properties were investigated. XPS spectra of SS-g-PLA copolymer showed C1S and N1S signals clearly and differed form that of the neat PLA. 2D HMBC NMR spectra showed correlation assigned to the carbon atom of PLA polymer chains and hydrogen atom in hydroxyl group of serine. Molecular weight of the graft copolymer by GPC was in range of 4000–5600 g mol−1. From soxhlet extraction, the results showed that PLA content in the graft copolymer molecules increased with increasing sericin content. The weight ratio of PLA to sericin in the SS-g-PLA5, SS-g-PLA10 and SS-g-PLA15 graft copolymers were 0.6:1, 1.4:1 and 2.1:1, respectively. By nitrogen analyzer,%protein increased significantly with increasing sericin content. Thermal analysis showed that the graft copolymer presented a single glass-transition temperature (Tg) belonging to PLA. This Tg decreased with increasing sericin content. The thermal degradation temperature (Td) of SS-g-PLA copolymer decreased to about 60 °C. Furthermore, SS-g-PLA is expected to utilize in biomedical applications.

A DFT-based study of the hydrogen-bonding interactions between myricetin and ethanol/water

Flavonoids are vital constituents of propolis that are responsible for its medicinal activity. Flavonoid extraction commonly employs ethanol and water as solvents. In the extraction reaction, hydrogen-bonding interactions play a crucial role. In this study, hydrogen-bonding interactions between myricetin-an abundant flavonoid in propolis-and ethanol or water were studied theoretically using density functional theory (DFT) methods. The molecular geometry and charge properties of the myricetin monomer were analyzed first. After careful optimization, nine stable myricetin-CH3CH2OH/H2O complex geometries were obtained. Hydrogen bonds were confirmed to exist in these optimized structures. The most stable structures were found to be those with hydrogen bonds involving the hydrogen atoms of hydroxyl groups and the oxygen atom of the keto group of myricetin. The characteristics of the hydrogen-bonding interactions in the optimized structures were carefully analyzed. The hydrogen bonds in the optimized geometries were shown to be closed-shell-type interactions. H5' in ring B of myricetin presented the strongest interaction. The hydrogen bonds were found to be Coulombic interactions. Those between the hydrogen atoms of the hydroxyl groups in myricetin and the oxygen atoms in CH3CH2OH and H2O were of moderate strength and had some covalent character, while the others were weak and were dominantly electrostatic in character.

Tannic acid-based adsorbent with superior selectivity for lead(II) capture: Adsorption site and selective mechanism

Rational design and directed synthesis of an adsorbent with superior selectivity is challenging but of utmost importance for the remediation of heavy metal-laden actual wastewater. In this work, a novel tannic acid (TA)-based adsorbent (TA@Zr) was synthesized by a simple coordination reaction. Adsorption isotherm experiments exhibited the TA@Zr had a high capacity for Pb2+ capture. Impressively, an outstanding selectivity with extremely high selective coefficient (40–170) can be achieved by the TA@Zr. With decrease of Zr precursor, the selectivity of as-synthesized TA@Zr remained unchanged, implying that the Zr species played a negligible role in the selectivity of TA@Zr. Even the Zr species were completely replaced by Ti precursor, the resultant adsorbent still possessed a remarkable selectivity. All these results revealed that it was the TA, rather than the Zr species, made a substantial contribution to the selectivity of TA@Zr. Further, based on the results of XPS, DFT and batch adsorption experiments, it can be deduced that the phenolic hydroxyl groups on TA functioned as the dominant adsorption sites in which the hydroxyl groups’ oxygen atoms coordinated with Pb2+ while hydrogen atoms of hydroxyl groups were replaced and released as hydrogen ions, thus extending a proton exchange mechanism for the selective adsorption of Pb2+ ions.

Complexation of Cu(BF4)2 with 3-hydroxyflavone in acetonitrile: quantum chemical calculation

In the article the results of the quantum chemical study of copper (II) solvato-complexes with acetonitrile (AN), tetrafluoroborate anion (BF4–) and 3-hydroxyflavone (flv) of the composition [Cu(AN)6]2+, [Cu(BF4)(AN)5]+, [Cu(flv)(AN)5]2+, [Cu(flv)(BF4)(AN)4]+ are presented. Calculations were done using density function theory (DFT) on the M06-2X/6-311++G(d,p) level of theory. Obtained results were interpreted in terms of complexes geometry and topology of electron density distribution using non-covalent interactions (NCI) approach. It was shown that flv molecule is a monodentate ligand in copper (II) complexes and coordinates central atom via carbonyl oxygen. Intramolecular hydrogen bond that exists in an isolated flv molecule was found to be broken upon [Cu(flv)(AN)5]2+ complex formation. In [Cu(flv)(AN)5]2+ complex, a significant rotation of phenyl ring over the planar chromone fragment was spotted as a consequence of intramolecular hydrogen bond breaking. Upon inclusion of BF4– anion to the first solvation shell of Cu2+, an intracomplex hydrogen bond was formed between hydrogen atom of hydroxyl group of flv molecule and the closest fluorine atom of BF4– anion. NCI analysis had shown that a hydrogen bond between hydrogen atom of hydroxyl group of flv molecule and the closest fluorine atom of BF4– anion is significantly stronger than intramolecular hydrogen bond in an isolated flv molecule. In addition, flexible phenyl ring of flv molecule in [Cu(flv)(BF4)(AN)4]+ complex was found to be internally stabilized by the weak van der Waals attraction between oxygen atoms of chromone ring and phenyl hydrogens. These evidences led to a conclusion that [Cu(flv)(BF4)(AN)4]+ complex is more stable, comparing to the in [Cu(flv)(AN)5]2+ complex.

Nanoscopic Study on Aliphatic Choline-Based Naphthenic Acid Ionic Liquids: Structural and Dynamical Properties.

The structural and dynamical properties of two cholinium-based naphthenic acid ionic liquids (CBNAILs), namely, cholinium cyclopentane carboxylate ([CH][CPC]) and cholinium cyclohexane carboxylate ([CH][CHC]) have been studied using the classical molecular dynamics simulations and quantum mechanical methods. The results have also been compared with corresponding aromatic ones. Interaction energies, charge transfers, and hydrogen bondings between the studied ion pairs were investigated by density functional theory calculations and also the theory of atoms in molecules. Density, mean-square displacement, self-diffusivity, viscosity, electrical conductivity, transference number, ionicity, and fragility have been computed for the studied CBNAILs in the temperature range of 298.15-450 K and at 0.1 MPa. The simulated values were in good agreement with experimental data where they exist. The structural features of these CBNAILs were characterized by calculating the partial site-site radial distribution functions and spatial distribution functions. The results show a density cap of hydrogen atoms of hydroxyl groups of cations extended along the COO- groups of anions. In these ILs, [CPC]- and [CHC]- are connected by hydrogen bonding to [CH]+ mainly through the carboxylate group. Increasing the number of carbon atoms in the ring of [CHC]- with respect to [CPC]- makes remarkable changes in self-diffusions, electrical conductivities, and viscosities. Altogether, this work gives a better insight into the dynamics and structuring of this class of biodegradable ILs at a molecular level.

Horseradish peroxidase immobilized on copper surfaces and applications in selective electrocatalysis of p-dihydroxybenzene

Horseradish Peroxidase (HRP) was immobilized on copper surfaces with the linker of L-Cysteine (L-Cys) self-assembled films to form Cu/L-Cys/HRP electrodes. The activity of HRP can be preserved by the Cu/L-Cys self-assembled films. The Cu/L-Cys/HRP electrodes can be used for the selective electrocatalytic oxidase of p-dihydroxybenzen in absent of H2O2. The optimum pH for electrocatalyzing p-dihydroxybenzen was 5.5 or 7.0, which corresponds to the isoelectric points of L-Cys and HRP, respectively. X-ray photoelectron spectroscopy (XPS) provided the evidence that L-Cys linked with Cu surface by the Cu S bond. Fourier transform infrared spectroscopy (FTIR) analyses indicated that aromatic plane of p-dihydroxybenzen was connected parallel to porphyrin ring of heme in HRP. Quantum chemical calculation of density functional theory (DFT) revealed that symmetry of molecular structure and minimum space steric hindrance for p-dihydroxybenzen were benefit to combination with HRP. Moreover, the lowest energy of LUMO and most negative charges of oxygen atom on hydroxyl group of p-dihydroxybenzen were advantage to lose the hydrogen atom of hydroxyl group to be oxided.

Reaction pathways of hydroxyl groups during coal spontaneous combustion

Hydroxyl groups are one of the key factors for the development of coal self-heating, although their detailed reaction pathways are still unclear. This study investigated the reaction pathways in coal self-heating by the method of quantum chemistry calculation. The Ar–CH2–CH(CH3)–OH was selected as a typical structure unit for the calculation. The results indicate that the hydrogen atoms in hydroxyl groups and R3–CH are the active sites. For the hydrogen atoms in hydroxyl groups, they are directly abstracted by oxygen. For hydrogen atoms in R3–CH, they are abstracted by oxygen at first and generate peroxy-hydroxyl free radicals, which abstract the hydrogen atoms in hydroxyl groups later. The reaction of R3–CH contains three elementary reactions, i.e., the hydrogen abstraction of R3–CH by oxygen, the conjugation reaction between the R3C■ and oxygen atom, and the hydrogen abstraction of –OH by hydroxyl free radicals. Then, the microstructure parameters, IRC pathways, and reaction dynamic parameters were respectively analyzed for the four reactions. For the hydrogen abstraction of –OH by oxygen, the enthalpy change and activation energy are 137.63 and 334.44 kJ/mol, respectively, which will occur at medium temperatures and the corresponding heat effect is great. For the reaction of R3–CH, the enthalpy change and the activation energy are −3.45 and 55.79 kJ/mol, respectively, which will occur at low temperatures while the corresponding heat influence is weak. They both affect heat accumulation and provide new active centers for enhancing the coal self-heating process. The results would be helpful for further understanding of the coal self-heating mechanism.

A Stable Amorphous Statin: Solid-State NMR and Dielectric Studies on Dynamic Heterogeneity of Simvastatin

Statins have been widely used as cholesterol-lowering agents. However, low aqueous solubility of crystalline statins and, consequently, reduced biovailability require seeking for alternative forms and formulations to ensure an accurate therapeutic window. The objective of the present study was to evaluate the stability of amorphous simvastatin by probing molecular dynamics using two nondestructive techniques: solid-state NMR and dielectric relaxation spectroscopy. Glassy simvastatin was obtained by the melt quench technique. (13)C cross-polarization/magic-angle-spinning (CP/MAS) NMR spectra and (1)H MAS NMR spectra were obtained from 293 K up to 333 K (Tg ≈ 302 K). The (13)C spin-lattice relaxation times in the rotating frame, T1ρ, were measured as a function of temperature, and the correlation time and activation energy data obtained for local motions in different frequency scales revealed strong dynamic heterogeneity, which appears to be essential for the stability of the amorphous form of simvastatin. In addition, the (1)H MAS measurements presented evidence for mobility of the hydrogen atoms in hydroxyl groups which was assigned to noncooperative secondary relaxations. The complex dielectric permittivity of simvastatin was monitored in isochronal mode at five frequencies (from 0.1 to 1000 kHz), by carrying out a heating/cooling cycle allowing to obtain simvastatin in the supercooled and glassy states. The results showed that no dipolar moment was lost due to immobilization, thus confirming that no crystallization had taken place. Complementarily, the present study focused on the thermal stability of simvastatin using thermogravimetric analysis while the thermal events were followed up by differential scanning calorimetry and dielectric relaxation spectroscopy. Overall, the results confirm that the simvastatin in the glass form reveals a potential use in the solid phase formulation on the pharmaceutical industry.

Synthesis and characterization of para- and meta-polybenzimidazoles for high-temperature proton exchange membrane fuel cells

In this article, two polybenzimidazoles (PBIs) were synthesized by the polycondensation reaction of 3,3′-diaminobenzidine with terephthalic acid ( p-PBI) or isophthalic acid ( m-PBI) for application in high-temperature proton exchange membrane fuel cells. Two kinds of purification (P1, P2) were applied to clean the polymers. The chemical structure of PBI polymers was confirmed using Fourier transform infrared (FTIR) spectroscopy. Polymers after P1 can be soluble and cast into film only from hot sulfuric acid solution (H2SO4), whereas both polymers after P2 were soluble in dimethylacetamide solution. Polymer films cast from H2SO4 were investigated using FTIR. The thermal stabilities of PBIs and PBI films were studied using the thermogravimetric analysis and the first derivative of the TG method. The temperature of 5% weight loss ( T5%) for both PBIs ranges from 136 to 312°C under nitrogen atmosphere, depending on the dicarboxylic acid used and the kind of purification. The PBI films exhibited T5% at 55°C because of the protonation of nitrogen atom in PBI by hydrogen atom of hydroxyl group in H2SO4. Electrical behavior of the two polymers was tested using electrochemical impedance spectroscopy for gold (Au)/PBI/Au architecture. For both measured polymers, Nyquist plots are presented with fittings based on circuit models.

Highlighting a π–π interaction: a protein modeling and molecular dynamics simulation study on Anopheles gambiae glutathione S-transferase 1-2

Cytosolic insect theta class glutathione S-transferases (GSTs) have not been studied completely and their physiological roles are unknown. A detailed understanding of Anopheles gambiae GST (Aggst1-2) requires an accurate structure, which has not yet been determined. A high quality model structure of Aggst1-2 was constructed using homology modeling and the ligand-protein complex was obtained by the docking method. Molecular dynamics (MD) simulations were carried out to study conformational changes and to calculate binding free energy. The results of MD simulation indicate that Aggst1-2 undergoes small conformational changes after ligands dock to the protein, which facilitate the catalytic reaction. An essential hydrogen bond was found between the sulfur atom of glutathione (GSH) and the hydrogen atom of hydroxyl group in Ser9, which was in good agreement with experimental data. A π-π interaction between Phe204 and CDNB ligand was also found. This interaction seems to be important in stabilization of the ligand. Further study of binding free energy decomposition revealed a van der Waals interaction between two ligands that may play a key role in nucleophilic addition reaction. This work will be a good starting point for further determination of the biological role of cytosolic insect theta class GSTs and will aid the design of structure-based inhibitors.

Comparison of antioxidant abilities of magnolol and honokiol to scavenge radicals and to protect DNA

The antioxidant properties of magnolol and honokiol were evaluated in the experimental systems of reducing ONOO− and 1O2, bleaching β-carotene in linoleic acid (LH) emulsion, and trapping 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS+) and 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH), and then were applied to inhibit the oxidation of DNA induced by Cu2+/glutathione (GSH) and 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH). Magnolol and honokiol were active to reduce ONOO− and 1O2. Honokiol showed a little higher activity to protect LH and to inhibit Cu2+/GSH-induced oxidation of DNA than magnolol. In addition, honokiol exhibited higher activities to trap ABTS+ and DPPH than magnolol. In particular, honokiol trapped 2.5 radicals while magnolol only trapped 1.8 radicals in protecting DNA against AAPH-induced oxidation. The obtained results suggested that low antioxidant ability of magnolol may be related to the intramolecular hydrogen bond formed between di-ortho-hydroxyl groups, which hindered the hydrogen atom in hydroxyl group to be abstracted by radicals. Therefore, the antioxidant capacity of magnolol was lower than that of honokiol.

A new photoproduct of 5-methylcytosine and adenine: a theoretical study

Both the cycloaddition mechanism of 5-methylcytosine with adenine and the deamination mechanism of the cycloaddition product have been studied using density functional theory method. The results suggest that the cycloaddition reaction could occur more easily through photochemical reaction pathway than through thermal reaction pathway. The obtained four-member ring structure could be easily transformed to an eight-member ring structure through bond cleavage of C5–C6 (the energy barrier is <2 kcal/mol). Then hydrolytic deamination reaction takes place with water assistance. The hydroxyl group of one water molecule attacks the C4′ atom and the hydrogen atom of another water molecule attacks N3′ atom to form a tetrahedral intermediate. Subsequently, the hydrogen atom of hydroxyl group transfers to N8′ to produce ammonia, and the amino group of the former 5-methylcytosine changes to carboxyl oxygen. Our calculations explain the phenomena that 5-methylcytosine and adenine could obtain the same photoproduct as thymine and adenine from theoretical aspects.

Stearic acid/polymethylmethacrylate composite as form-stable phase change materials for latent heat thermal energy storage

The aim of this research is to prepare of a novel form-stable composite phase change material (PCM) for the latent heat thermal energy storage (LHTES) in buildings, passive solar space heating or functional fluid by entrapping of SA into PMMA cell through ultraviolet curing dispersion polymerization. The composite PCM was characterized using scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis technique. The results show that the form-stable microencapsulated PCM with core/shell structure was formed and the maximum encapsulated proportion of SA in the composite was 51.8 wt.% without melted PCM seepage from the composite. In the shape stabilized microencapsulated PCM, the polymer acts as supporting material to form the microcapsule cell preventing the leakage of PCM from the composite and the SA acts as a PCM encapsulated in the cell of PMMA resin. The oxygen atom of carbonyl group of skeleton is interacted with the hydrogen atom of hydroxyl group of SA. Thermal properties, thermal reliability and heat storage/release performance of the composite PCM were determined by differential scanning calorimetry (DSC), FT-IR and thermal cycling test analysis. The melting and freezing temperatures and the latent heats of the composite PCM were measured as 60.4 °C, 50.6 °C and 92.1 J/g, 95.9 J/g, respectively. The results of DSC, FT-IR and thermal cycling test are all show that the thermal reliability of the composite PCM has an imperceptible change. This conclusion indicates that the composite has a good thermal and chemical stability.

Synthesis, characterization, and adsorption behavior of aniline modified polystyrene resin for phenol in hexane and in aqueous solution

Macroporous crosslinked poly( p-vinylbenzylaniline) (PVBA) was synthesized and its adsorption isotherms for phenol in hexane and in aqueous solution were comparatively measured. It was shown that the adsorption isotherms in hexane were straight lines and passed through the origin, whereas those in aqueous solution could be simulated by Freundlich isotherms. Adsorption enthalpies of phenol onto PVBA were calculated, and the results indicated that the adsorption was an exothermic process. Comparison of the adsorption behaviors of PVBA, poly( p-vinylbenzylmethylamine) (PVBMA), and poly( p-vinylbenzyl- p-nitroaniline) (PVBNA) for phenol in hexane suggested that hydrogen bonding and π – π stacking were primarily responsible for the adsorption, the nitrogen atom and benzene ring of PVBA acted as hydrogen bonding acceptors and formed hydrogen bonding with the hydrogen atom of hydroxyl group of phenol. Investigation of the adsorption mechanism in aqueous solution revealed that hydrogen bonding and hydrophobic interaction were the main driving forces.