Thermal stability of organosilica and their forms modified by ions of copper(II)

Thermal stability of two-component organosilica sorbents – silico-polymethylsiloxanes with the ratio of hydrophilic and hydrophobic components of 50:50 and 70:30 mass%, and their forms, modified by copper(II), was investigated using thermal analysis (DTG, DTA, TG). The influence of the composition of modified organosilica sorbents and copper(II) content on the endothermic (removal of adsorbed water) and exothermic (decomposition by oxidation of methyl groups, possible hydration of surface) peak temperatures and on mass loss is shown. It was found that thermal stability of organosilica modified by copper(II) was lower than that of initial sorbents and depends on the content of modifying component and ratio of silanol and methylsilil groups in organosilica composition.     

Carbon,natural and synthetic sorbents for decontamination of objects of ecosystems from pathogenic microflora

Physico-chemical characteristics and sorption activity of carbon, organosilica sorbents and their modified forms towards proteins, possessing specific activity, and cholerae vibrio have been studied. It was found, that carbon materials modified by copper (II) effectively extracts cholerae vibrio (100%) and may be recommended for disinfection of drinking water. Sorption capacity of organosilica sorbents and their modified by copper (II) forms towards pathogenic microflora (E.coli, St.aureus, Ps.aeruginosa) depending on the composition of the sorbents, concentration of the modified reagent, pH of medium have been evaluated. The rows of the increase of sorption of pathogenic microorganisms by synthetic sorbents in water-salt solutions were established: Al(III)<Zn(II)<Cu (II). It was shown that inhibiting effect of modified synthetic organosilica and natural sorbents towards such pathogenic microorganisms as E-coli, St.aureus Ps.aeruginosa and fungus Bacillus pyocyaneus accordingly is equal 80–98%.     

Interaction between bilirubin and sodium deoxycholate and their adsorption from mixed solutions on the surface of silica sorbents

The interaction between the bile pigment bilirubin and sodium deoxycholate is studied in aqueous buffer solutions at pH 7.4. It is established that bilirubin forms strong complexes with deoxycholate trimers. The complexation constant is determined by spectrophotometry. The adsorption of bilirubin and sodium deoxycholate from their mixed solutions on the surface of a hydrophilic and two hydrophobic silica sorbents is investigated. It is shown that bilirubin is adsorbed on the surface of all these sorbents only in the free state. Sodium deoxycholate is adsorbed in the forms of monomers and trimers. The affinity of all adsorbed particles is higher for hydrophobic silica sorbents. The binding constants of bilirubin, as well as monomers and trimers of deoxycholate, with the surfaces of all examined sorbents are determined.     

Thermally-regulated molecular selectivity of organosilica sol-gels

The feasibility of using temperature as a control mechanism for altering the selectivity of organosilica sol-gels for a specific molecule is demonstrated in this communication. The porous organosilica sol-gels act as reversible thermoresponsive materials which become hydrophobic at higher temperature and hydrophilic at lower temperature. When exposed to a mixture of molecules, the gels selectively intake the more hydrophobic species at higher temperature. A particularly remarkable feature of these gels is their ability to preferentially sequester the hydrophobic molecule at high temperature and the hydrophilic species at low temperature. Finally, these gels selectively intake hydrophobic molecules at high temperature and then preferentially release them when the temperature is lowered.     

Effect of mechanical activation on the thermal stability of polytetrafluoroethylene powder

It was found that processing in a planetary activator leading to amorphization of the structure of polytetrafluoroethylene powder was not accompanied by a noticeable decrease in its thermal stability. It was established that the temperature at the onset of melting drops slightly, the melting rate increases, and the enthalpy of the endoeffect declines noticeably heating.     

The surface energy of hydrophilic and hydrophobic adsorbents

Water vapor adsorption and heats of water wetting are studied for hydrophilic quartz, hydrophobic-hydrophilic talc, and hydrophobized Silochrom samples. Water contact angles on the materials under examination are found. The surface thermodynamic parameters of the sorbents are calculated from the data obtained. It is shown that boundary water layers on hydrophilic quartz surface are ordered to a higher extent, while those on hydrophobic basal surfaces of talc particles and hydrophobic surfaces of modified Silochrom samples are ordered to a lower extent relative to liquid water. An empirical equation relating the surface pressure of water films adsorbed on hydrophilic high-energy surfaces with the surface free energy of the latter is proposed. The values of surface free energy are estimated from this equation for a number of important hydrophilic adsorbents.     

Thermal degradation of polyethylene containing antioxidant and hydrophilic/hydrophobic silica

High-density polyethylene, its composites with hydrophilic/hydrophobic silica and the antioxidant BHT (butylated hydroxytoluene) were studied using the thermogravimetric analysis. It has been shown that filling with silica as well as introducing BHT into the unfilled polymer increases the thermal-oxidative stability of the polymer. Immobilized BHT is inactive and it suppresses the stabilizing effect of hydrophobic silica surface in the processes of thermal oxidation at the initial stage. However, being gradually released from the surface antioxidant prolongs the resistance of the polymer against oxidation.     

Immobilization of Enzymes by Radiation-Induced Copolymerization of 2-Hydroxyethyl Methacrylate and Other Hydrophilic or Hydrophobic Comonomers

Immobilization of enzymes by radiation-induced copolymerization was studied at low temperatures by use of various comonomer systems consisting of 2-hydroxyethyl methacrylate and other more hydrophilic or hydrophobic comonomers. The matrices obtained by copolymerization with more hydrophilic and more hydrophobic comonomers decreased the porosity in the matrix equally. However, the activity yield of the immobilized enzyme showed different changes with repeated use in the more hydrophilic and more hydrophobic matrices. That is, the initial activity decreased rapidly with repeated use owing to the enzyme leakage from the matrix, in the increased hydrophilic matrices. On the other hand, in the more hydrophobic matrices enzyme leakage was completely retarded and activity did not change with repeated use. Moreover, the activity yield showed a maximum at a certain monomer composition in the copolymerization with hydrophobic comonomer. Finally, it was found that the maximum activity yield of the hydrophobic matrices was larger in general than that of the hydrophilic copolymer matrices.     

Surface energy of hydrophobic adsorbents

The adsorption of water vapor and the heat of wetting of hydrophilic hydromica and hydrophobized samples of kaolinite and Silochrom were studied. The contact angles for the wetting of the investigated materials with water were obtained. The thermodynamic characteristics of the surface of the sorbents and the interfacial region at their boundary with water were calculated from the obtained data. It was shown that the boundary water layers close to the hydrophilic surface of the hydromica are more ordered while those close to the hydrophobic surfaces of the modified samples of kaolinite, Silochrom, and the reference sample (extremely hydrophobic Teflon) are less ordered than liquid water. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 87–91, March–April, 2006.     

Interaction of Water and Methanol Molecules with the Surface of Carbonaceous Materials According to Gas Chromatographic Data

We have used gas chromatography to study the interaction of water and methanol molecules with active hydrophilic centers on the surface of thermally expanded graphite and graphitized thermal carbon black. We have determined the concentration of carboxyl and phenol hydroxyl groups on the surface of the sorbents and the heats of adsorption for adsorption of the studied substances on these groups. We have shown that water molecules are adsorbed as clusters on the hydrophilic centers of the studied sorbents at very low relative pressures, with n = 2 molecules in the cluster.     

Effect of chemical structure and crystallinity on sorption,diffusion and chemical stability of polyurethaneacetals

The diffusion of water in non-isocyanate polyurethaneacetals (PUA) of various kinds and compositions has been studied. The direct relationship between the composition of polymers, their degree of crystallinity, morphology and diffusional characteristics has been demonstrated. It has been shown that by changing the polymer composition one can obtain hydrated polymer systems of every type, hydrophobic, hydrophilic and moderately hydrophilic. The kinetics of hydrolytic degradation of PUA in HCl solutions (pH = 0·1) between 20 and 75°C has been investigated. Hydrolysis of acetal bonds has been found to occur in the amorphous phase of a polymer sample, which is mostly formed by the fragments of urethane glycol.The influence of morphology on PUA diffusional characteristics and their stability to hydrolysis has been determined.It has been shown that the physico-chemical properties of PUA can be regulated without the introduction of new compounds.     

Periodic mesoporous organosilicas with co-existence of diurea and sulfanilamide as an effective drug delivery carrier

In this article we report the synthesis of new periodic mesoporous organosilicas (PMOs) with the co-existence of diurea and sulfanilamide-bridged organosilica that are potentially useful for controlled drug release system. The materials possess hexagonal pores with a high degree of uniformity and show long-range order as confirmed by the measurements of small-angle X-ray scattering (SAXS), N₂ adsorption isotherms, and transmission electron microscopy(TEM). FT-IR and solid state ²⁹Si MAS and ¹³C CP MAS NMR spectroscopic analyses proved that the bridging groups in the framework are not cleaved and covalently attached in the walls of the PMOs. It was found that the organic functionality could be introduced in a maximum of 10 mol% with respect to the total silicon content and be thermally stable up to 230 °C. The synthesized materials were shown to be particularly suitable for adsorption and desorption of hydrophilic/hydrophobic drugs from a phosphate buffer solution at pH 7.4.     

Polyelectrolyte sorbents based on aliphatic ionenes for ion chromatography

2-4, 3-4, 2-8, 3-8, 3-6, 4-6, 6-8, 6-10-ionenes (polymers with quaternary nitrogen atoms in the main chain) served as modifiers in synthesizing polyelectrolyte sorbents for ion chromatography. The approaches to the synthesis and their stability are discussed. Cluster analysis was applied to separate aliphatic ionenes to three groups as chromatographic modifiers, namely hydrophilic, hydrophobic, and intermediate. Each group is characterized by a certain selectivity to sulfate, perchlorate, iodide and thiocyanate. The sorbents show high selectivity and efficiency up to 15 000 theoretical plates per meter.     

Nanosilica-reinforced UV-cured polyurethane dispersion

UV-curable polyurethane dispersions (UV–PUDs) have been reinforced with hydrophobic and hydrophilic modified silicas, respectively, and the effects have been studied with dispersion and dispersion cast films. It has been found that particle size increased and water swell decreased, tensile modulus, strength, and thermal stability increased with the addition and increasing amount of silica. These effects were more pronounced with the hydrophilic modified one than the hydrophobic modified one.     

Neutron scattering study of water confined in periodic mesoporous organosilicas

A series of quasi-elastic neutron scattering measurements were performed using IN6 at the Institute Laue Langevin for a mesoporous organosilica material with phenyl functions, called phenyltriethoxysilane (PTES). The aim of the experiment was to study the diffusion dynamics of nano-scale water clusters inside the hydrophobic pores as a function of temperature and hydration. By fitting the Debye-Waller factor, the data show clearly the different behavior between water, both inside and outside the hydrophobic pores, which resembles bulk water. The mean thermal displacement 〈u²〉 of the external water increases with T almost linearly up to 353 K, while the internal water quickly reaches the maximum at T∼323 K, indicating the confinement by an averaged pore diameter of the porous organosilica.     

Nanoparticles based on polyelectrolyte complexes: effect of structure and net charge on the sorption capability for solved organic molecules

 The sorption of solved organic molecules such as p-nitrophenol or dyes on previously formed nanoparticles based on polyelectrolyte/micelle complexes or polycation/polyanion complexes was studied. It could be shown that the sorption capability strongly depends on the structure and properties of the complex particles. Investigations have been made with complex particles that differ in their hydrophobic/hydrophilic structure, size and net charge. Such complex aggregates could be prepared by mixing the cationic surfactant dodecylamido-ethyldimethylbenzylammonium chloride, the polycations poly(diallyldimethylammonium chloride) or poly(methacryloyloxyethyldimethylbenzylammonium chloride) and the copolymers of maleic acid with propene or methylstyrene as anionic components. It is found that the sorption capability increases with increasing molar mass and hydrophobic properties of the components used. In addition, the concentration ratio c _polym/c _org.poll that was required to reach optimal sorption conditions could be decreased by the use of macromolecules with high molar masses. The best results were obtained by using cationic stabilized complex particles formed with high-molar-mass polycations as sorbents for anionic dye molecules. Received: 10 November 1999 Accepted: 24 February 2000     

大港常压渣油临氮与临氢热反应过程中胶体稳定性变化研究

对比了大港常压渣油临氮和临氢热反应过程中的胶体稳定性变化。结果表明,随着反应时间的延长,在热反应生焦诱导期内,渣油样品的胶体稳定性迅速下降;开始生焦后,胶体稳定性缓慢下降。从组分组成和组分性质角度,对大港常压渣油样品在热反应过程中胶体稳定性变化原因进行了分析。结果表明,随着反应时间的延长,沥青质含量先上升、后下降,在生焦诱导期结束时达到最大值,与体系胶体稳定性的变化特征相一致。随着热反应的进行,饱和分和轻芳烃组分的含量在上升,重芳烃、轻胶质、中胶质、重胶质含量下降,临氮热反应过程中轻胶质、中胶质、重胶质含量的下降更为显著。对渣油样品各组分的数均相对分子质量和平均偶极矩进行了研究。结果表明,随着热反应的进行,轻、中、重胶质组分的数均相对分子质量和平均偶极矩呈下降趋势,而沥青质的数均相对分子质量和偶极矩先增大后减小,从而使沥青质和胶质的分子性质差别先增加后减小,与体系胶体稳定性的变化趋势一致;同时沥青质的偶极矩变化表明,强极性的沥青质优先聚集生焦、临氢热反应过程中,氢与催化剂的作用有助于抑制沥青质分子量增大和极性增强,从而有助于抑制生焦。     

聚乙二醇-b-聚对苯二甲酸丁二醇酯嵌段共聚物降解行为的研究

研究了系列PEG-b-PBT嵌段共聚物在pH=7.4磷酸盐缓冲溶液中和37℃条件下的体外降解行为.同时观察了水解降解过程中系列共聚物溶胀率、失重、特性粘度、结晶度和表面形态等方面的变化.实验结果表明,嵌段共聚物的组成直接影响其水解降解性能,共聚物的溶胀率和失重率随聚醚组分含量而增大;通过调节共聚物的组分比可以达到调节降解速率的目的.此外研究还表明,共聚物最初的降解主要发生在软段和硬段相联的酯键上.     

Interaction of Enzyme with Polymer Matrix in Immobilized Enzymes

Thermolysin was immobilized by radiation polymerization of hydroxyalkyl acrylate and tetradecaethylene glycol dimethacrylate monomers at low temperatures in the presence of the enzyme, and the degree of interaction of the enzyme with the polymer matrix was studied by measuring the thermal stability of the immobilized enzyme. The thermal stability was affected by the molecular structure of the monomer; the thermal stability of the immobilized enzyme from hydrophilic monofunctional monomers in the wet state was higher than that from hydrophobic bifunctional monomers. The thermal stability in polymers formed from hydroxy-alkyl acrylates decreased with an increase in the number of methylene units in the monomer, owing to a change of the state of the enzyme trapped in the porous polymer matrix. The enzyme molecule trapped in a hydrophilic porous polymer matrix appeared to be stabilized by interaction with the polymer chains.     

pH敏感性两亲聚合物网络PAA—l—PTHF的研究

以具有良好柔性和生物相容性的聚四氢呋喃（ＰＴＨＦ）为疏水链段,具有ｐＨ敏感性的聚丙烯酸（ＰＡＡ）为亲水链段,通过ＰＴＨＦ双端基大分子单体与丙烯酸自由基共聚,首次合成了聚丙烯酸－ｌ－聚四氢呋喃（ＰＡＡ－ｌ－ＰＴＨＦ）两亲聚合物网络,并对网络的结构、组成以及交联点密度进行了表征。两亲聚合物网络溶胀行为研究表明,ＰＡＡ－ｌ－ＰＴＨＦ既能在水中溶胀又能在有机溶剂中溶胀,在水中的溶胀度随网络亲水链段ＰＡＡ含