An ESCA study of the photo-oxidation of the surface of polystyrene film

The surface photo-oxidation of polystyrene film is examined using ESCA. The initial stage involves the formation, primarily, of CO groups on the surface. Further reaction produces carbonyl, carboxyl and carbonate groups, accompanied by the disappearance of the C_1s shake-up satellite peaks, indicating the photo-oxidation of the phenyl groups. The relative concentrations of these groups at the surface are followed as a function of oxidation time. The $\text{C}\text{O}$ peak intensity ratio indicates a limiting C:O stoichiometry in the surface of ～ 1·7:1, very different from the bulk of the polymer. Carboxyl groups predominate in this highly oxidised surface.     

取代基对木质素三聚体模型化合物醚键均裂反应影响的密度泛函理论研究

利用密度泛函理论M062X/6-31++G(d,p)方法,对27种具有不同取代基(甲基、羟甲基和甲氧基)的木质素三聚体模型化合物的Cα-O和Cβ-O键均裂解离能进行了理论计算,探究了不同位置取代基对醚键解离能的影响规律。结果表明,当R2或R3位氢原子仅有一个被甲氧基取代时,Cβ-O键解离能变化很小;当R2、R3位氢原子均被甲氧基取代时,Cβ-O键解离能明显降低;且R4、R5位甲氧基能强化R2、R3位甲氧基对Cβ-O键解离能的降低程度,而不受R1位取代基的影响。当R4、R5位氢原子相继被甲氧基取代时,Cα-O键解离能逐渐降低,且R2、R3位甲氧基也能强化R4、R5位甲氧基对Cα-O键解离能的降低程度。当R1位氢原子相继被甲基、羟甲基取代时,Cα-O键解离能逐渐升高,然而R2、R3位甲氧基会弱化R1位甲基、羟甲基对Cα-O键解离能的升高程度;R1位甲基不会影响Cβ-O键解离能,羟甲基却能明显提高Cβ-O键解离能。     

Sulfur-containing amino acids of the polyhedral protein of the silkworm yellows virus

Conclusions 1. The polyhedral protein of silkworm virus yellows isolated by the alkali method does not contain sulfhydryl groups.2. The content of sulfhydryl groups in the reduced polyhedral protein has been determined by titration with methylmercury nitrate and by means of Ellman's reagent (0.029–0.033 µmole of SH groups per mg of protein). The content of S-carboxymethylcysteine groups in acid hydrolysates of reduced and carboxymethylated polyhedral protein has been determined with an amino acid analyzer (0.03 µmol/mg).3. The content of cysteic acid in acid hydrolysates of oxidized polyhedral protein is 0.069 µmole/mg.Khimiya Prirodnykh Soedinenii, Vol. 4, No. 3, pp. 174–178, 1968     

The effect of the counterion composition on the chain restriction in the cationic polymerization of isobutylene

The effects of the nature of halogens in the initiatingtert-butyl halide-aluminum-containing Lewis acid system on the number average molecular weightM _n and the structure of end groups of polyisobutylene macromolecules obtained in the cationic polymerization of isobutylene in hexane at -78 °C were studied. An increase inM _n is observed in the transition from chlorine to bromine and iodine, accompanied by a decrease in the fraction of end C=C groups and an increase in the relative content of C-Hal groups (Hal = Cl, Br, and I). When atoms of different halogens are present in the counterion, more bulky atoms preferentially participate in the formation of the end groups. The results are interpreted within the framework of the principle of hard and soft acids and bases.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1184–1187, May, 1996.     

A study of the interaction of dimethylcadmium and diethylcadmium with the Aerosil surface by IR spectroscopy and mass spectrometry

Dimethyl- and diethylcadmium interact with both free hydroxyl and siloxane groups of the Aerosil surface to form ≡Si-O-Cd-C≡ and ≡Si-H fragments. At 200 °C these structures undergo β-elimination to form surface ≡Si-O-Cd-H groups. It has been established that on heating to 600 °C, these groups decompose to afford metallic cadmium with the regeneration of the ≡Si-OH surface groups. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1717–1720, October, 1993.     

Protecting and Leaving Functions of Trimethylsilyl Groups in Trimethylsilylated Silicates for the Synthesis of Alkoxysiloxane Oligomers

The concept of protecting groups and leaving groups in organic synthesis was applied to the synthesis of siloxane‐based molecules. Alkoxy‐functionalized siloxane oligomers composed of SiO₄, RSiO₃, or R₂SiO₂ units were chosen as targets (R: functional groups, such as Me and Ph). Herein we describe a novel synthesis of alkoxysiloxane oligomers based on the substitution reaction of trimethylsilyl (TMS) groups with alkoxysilyl groups. Oligosiloxanes possessing TMS groups were reacted with alkoxychlorosilane in the presence of BiCl₃ as a catalyst. TMS groups were substituted with alkoxysilyl groups, leading to the synthesis of alkoxysiloxane oligomers. Siloxane oligomers composed of RSiO₃ and R₂SiO₂ units were synthesized more efficiently than those composed of SiO₄ units, suggesting that the steric hindrance around the TMS groups of the oligosiloxanes makes a difference in the degree of substitution. This reaction uses TMS groups as both protecting and leaving groups for SiOH/SiO⁻ groups.     

Structural Characteristics of Silica Gel Modified with Organosilicon Compounds According to the Data on the Adsorption of Water and n-Hexane Vapors

The adsorption of water, n-hexane and nitrogen vapors on the mesoporous silica gel with the grafted aminopropyl, mercaptopropyl and dimercaptodipropyl groups is investigated. It is shown that aminopropyl groups are oriented in parallel, whereas the mercaptopropyl ones are either vertical or tilted to the initial sorbent surface. The surface area of silica gel that is free of modifiers, as well as the number of vicinal and isolated OH groups are estimated. It is established that hydrogen bonds between the NH₂ groups of aminopropyl radical and isolated OH groups of silica gel are ruptured after the saturation of sorbent with water vapors at a relative pressure of about 0.5. Based on adsorption data, it is concluded that the most of 3-aminopropyltriethoxysilane interacts with the isolated OH groups of silica gel with a stoichiometric coefficient equal to unity.     

Anionic polymerization of caprolactam—LII. Effect of reaction conditions on the content of acidic and basic groups in the polymer

The concentration of acidic groups in water-extracted polymers at rather short reaction times and temperatures of about 200° is predominantly determined by the initial concentration of activator; at higher temperatures and long reaction times, the concentration of acidic groups depends in the first place on the initial concentration of sodium caprolactam as initiator. The acidic groups are not composed of carboxylic groups only; some of the groups are due to the hydrolysis of labile structures during extraction of the polymer with boiling water. While the concentration of acidic groups in the polymer approximately attains the initial concentration of sodium caprolactam, the concentration of basic groups in the polymer may exceed this value several times. The rate of formation of basic groups is proportional to the instantaneous concentration of the strong base.     

Synthesis of the C-terminal tetrapeptide of the oxytocin sequence using various protective groups for the cysteine thiol function

The synthesis of amides of tetrapeptides with the 6–9 sequence of oxytocin containing various protective groups for the thiol function has been performed by 2+2 and 1+3 schemes. Relationships between the yield of tetrapeptide and the structures of the protective groups have been obtained. An advantage of trityl and benzyl protective groups for masking the tiol function of cysteine has been shown. The signals of the¹³C NMR spectra of the compounds obtained have been interpreted.All-Union Scientific-Research Institute of Blood Substitutes and Hormone Preparations, Moscow. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 400–406, May–August, 1992.     

Probing the protein–nanoparticle interface: the role of aromatic substitution pattern on affinity

A new class of cationic gold nanoparticles (NPs) has been synthesised bearing benzyl moieties featuring –NO₂ and –OMe groups to investigate the regioisomeric control of aromatic NP–protein recognition. In general, NPs bearing electron-withdrawing groups demonstrated higher binding affinities towards green fluorescent protein (GFP) than NPs bearing electron-donating groups. Significantly, a ～7.5- and ～4.3-fold increase in binding with GFP was observed for –NO₂ groups in meta-position and para-position, respectively, while ortho-substitution showed binding similar to the unsubstituted ring. These findings demonstrated that the NP–protein interaction can be controlled by tuning the spatial orientation and the relative electronic properties of the aromatic substituents. This improved biomolecular recognition provides opportunities for enhanced biosensing and functional protein delivery to the cells.     

Some observations on the liquid immiscible nature of the Iron-Indium and Aluminium-Indium Systems

Hydroxide Groups on Zeolites. IV. Formation of Hydroxide Groups by Reduction of Y-Zeolites Containing Transition Metal Ions The formation of hydroxide groups as result of the reduction is studied by IR spectroscopy on NiNaY, CuNaY, and ZnNaY zeolites. After transformation of the OH groups into OD groups it was found that D₂ reduces the transition metal ions at 350°C and that simultaneously the concentrations of two types of the hydroxides groups which are already present before this treatment are increased markedly, viz. the concentration of an acid species and that of a weakly acid species. In NiNaY and CuNaY zeolites, the reduction at 350°C proceeds much more slowly than in ZnNaY zeolites. The reduction of ZnNaY zeolites is connected with their transformation to ultrastable zeolites.     

活性炭催化碳酸二甲酯水解行为的研究

以无氯Cu/AC催化剂中活性炭载体为研究对象,对活性炭上DMC水解反应条件进行了考察,并通过Boehm滴定法和XPS对活性炭上DMC水解活性位点进行了分析。结果表明,温度的升高和水含量的增加对DMC水解有较大的促进作用,较高的压力和CO₂气氛对DMC水解有一定的抑制作用,甲醇量和CO、O₂、N₂气氛对DMC水解影响较小。不同条件处理的活性炭表面基团种类、数量均有较大变化,HNO₃处理使活性炭碱性基团含量下降,羧基等酸性含氧官能团含量明显增加,总酸量最高可达1.88 mmol·g^-1;先HNO₃后NaOH处理的活性炭上酸性基团含量大量减少,表面碱性基团含量则有较大提高,总碱量最高可达1.69 mmol·g^-1。特别地,活性炭表面碱性基团是催化DMC水解的活性位点,在活性炭碱性基团含量由0.16增加到1.69 mmol·g^-1的过程中,DMC水解程度由2.5%增加到了31.7%,而酸处理可以有效降低活性炭表面碱性基团含量,抑制其催化DMC的水解性能。     

Method for determining the positions of sulfate groups in sulfated carbohydrates

A new method of determining positions of the sulfate groups in sulfated carbohydrate-containing compounds is described which consists in the direct replacement of the sulfate groups by formyl groups through the action on these compounds of chloromethylenediethylammonium chloride in dimethyl formamide. Subsequent chromatomass spectrometry permits the determination of the positions of the formyl groups and, consequently, of the initial sulfate groups. The replacement of sulfate groups by formyl groups under these conditions takes place both in sulfated monomeric and polymeric compounds. The stability of the formyl group in peracetylated monoformates under the conditions of acetolysis has been shown, and in the case of polymeric compounds this permits the determination of the positions of formyl and sulfate groups. Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 607–612, September–October, 1980.     

Decorating step-by-step and independently the surface and the core of dendrons

Dendrons possessing one activated vinyl group at the core and several chlorine atoms at the end of the branches are used as starting materials to study the possibility to react independently the surface functions and the core function. In particular, the most powerful sequence of reactions for decorating them by organometallic complexes as end groups and amine or alcohol at the core has been determined. In the first step, phenol phosphines are grafted as end groups of the dendrons, and they can be used for the complexation of metals. However, these phosphines must be kept free when amines are used to react with the vinyl core in the next step. Depending on the type of phosphine end groups and on the type of function of the core (amine or alcohol), the complexation of ruthenium ([RuCl₂(p-cymene)]₂) and rhodium ([RhCl(COD)]₂) derivatives by the phosphine end groups can occur without side reaction at the core.     

Model cationic flocculants from the Mannich reaction of polyacrylamide

¹⁴C-Labeled cationic derivatives of polyacrylamide were prepared by the reaction of polyacrylamide with ¹⁴C-labeled formaldehyde and dimethylamine hydrochloride. The resulting Mannich base was reacted with dimethyl sulfate. Both reactions produced a yield of about 50% and the final product was a substituted polyacrylamide with tertiary and quaternary amine groups. Extensive dialysis removed the tertiary groups to give a stable radio-labeled polymer that was an effective flocculant. Treatment with mixed-bed ion exchange resin was effective in purifying polyacrylamide derivatives; however, counterions for the quanternary amine groups were not quantitatively exchanged for hydroxide groups.     

Self-organization of sulfopolystyrene ionomers in solutions: Dependence on the polarity of the solution and the content of ionogenic groups in chains

The self-organization of ionomers of sulfonated polystyrene containing different amounts of SO₃Na ionogenic groups (0.5, 1.35, and 2.6 mol %) in three solvents (benzene, toluene, and THF) is studied via the methods of neutron scattering. It is shown that, in toluene, ionogenic groups form “effective” chains of up to 10–20 macromolecules owing to aggregation. In benzene, chains of both the PS precursor and ionomers are surrounded by volume solvate shells in the form of ∼4-nm-dia tubes that hamper interaction between ionomers via ionogenic groups. The tendency of ionomer chains toward aggregation in benzene is enhanced as the content of polar groups in chains is increased to 2.6 mol %. The diameter of solvate shells around chains decreases to ∼1 nm, and chains associate to form denser structures. In this case, the degree of integration of macromolecules turns out to be smaller than that in toluene. In THF, the processes of solvation and structuring of PS precursor chains are well defined and compete with tendencies toward association through ionogenic groups in solutions of ionomers. The formation of developed supramolecular structures in THF is hindered by the shielding of the potentials of interaction between ion pairs because of a high dielectric constant of the solvent.     

活性炭催化碳酸二甲酯水解行为的研究

以无氯Cu/AC催化剂中活性炭载体为研究对象,对活性炭上DMC水解反应条件进行了考察,并通过Boehm滴定法和XPS对活性炭上DMC水解活性位点进行了分析。结果表明,温度的升高和水含量的增加对DMC水解有较大的促进作用,较高的压力和CO_2气氛对DMC水解有一定的抑制作用,甲醇量和CO、O_2、N_2气氛对DMC水解影响较小。不同条件处理的活性炭表面基团种类、数量均有较大变化,HNO_3处理使活性炭碱性基团含量下降,羧基等酸性含氧官能团含量明显增加,总酸量最高可达1.88 mmol·g~(-1);先HNO_3后NaOH处理的活性炭上酸性基团含量大量减少,表面碱性基团含量则有较大提高,总碱量最高可达1.69 mmol·g-1。特别地,活性炭表面碱性基团是催化DMC水解的活性位点,在活性炭碱性基团含量由0.16增加到1.69mmol·g~(-1)的过程中,DMC水解程度由2.5%增加到了31.7%,而酸处理可以有效降低活性炭表面碱性基团含量,抑制其催化DMC的水解性能。     

Interaction of Globular Albumins with the Silica Surface

Bovine serum albumin macromolecules interact with vicinal hydroxyl groups of the silica surface at carbonyl groups and with isolated surface hydroxyl groups at the imide groups. Geminal surface hydroxyl groups behave as single adsorption sites relative to albumin adsorption. The concentration of such groups on a quartz surface was evaluated. The secondary structure of globular albumins is altered as the result of interaction in the silica–globular albumin system. Extended -segments appear on the surface and the concentration of -spirals decreases. This alteration leads to change in the tertiary globular structure of the albumin. The adsorption of albumin macromolecules on the silica surface is inclined.     

Liquid-Crystalline copolymers and polymer blends containing electron donor and acceptor groups: Effects of mesogenic structures on the smectic phase and the miscibility

Side-chain liquid-crystalline copolymers and polymer blends containing an electron-donating (carbazolylmethylene)aniline group and electron-accepting nitrophenyl groups with various central linking groups between aromatic groups in the mesogenic units, i.e., N?CH, CH?CH, N?N, and COO, were prepared to examine effects of the mesogenic structure on thermal behaviours. The most remarkable effects of the central linking group on the thermal properties and the miscibility were observed for the polymer blends. The 1:1 miscible polymer blends were prepared from the electron-donating polymer containing (carbazolylmethylene)aniline group (PM6C_z) and the electron-accepting polymers with similar central linking groups, i.e., N?CH, CH?CH, and N?N. For example, the 1: 1 polymer blend of PM6C_z and the electron-accepting polymer containing the nitrostilbene group induced a smectic phase from 73 to 207°C. This isotropic temperature was 46°C higher than the calculated value (161°C) based on the composition without the electron donor-acceptor interaction. On the other hand, the 1: 1 polymer blend of PM6C_z and the electron-accepting polymer containing the nitrophenylbenzoate group showed phase separation. Thus, the remarkable thermal stability and the miscibility of the polymer blends containing the electron donor and acceptor groups might be caused by planar structures between the mesogenic side groups which have similar central linking groups through the electron donor-acceptor interaction. A similar tendency was seen for copolymers and binary mixtures of both low-molecular-weight compounds containing the same mesogenic groups. © 1995 John Wiley & Sons, Inc.     

亚碘酰苯氧化Schiff碱配合物反应的取代基效应研究

用紫外-可见分光光度分析法测定了PhIO氧化系列新型Schiff碱双核配合物的反应动力学及取代基效应.结果表明,这些配合物与PhIO的反应在动力学上为一级反应;这些配合物的环外苯基及环上亚苯基上吸电子取代基均能提高抗氧化稳定性,而给电子取代基的作用则相反;环上亚苯基上的取代基效应比环外苯基上的取代基效应更明显;氧化反应速率常数k与环外苯基上的取代基特性常数σ(σ_m或σ_p)及环上亚苯基上的取代基特性常数(σ_m+σ_p)呈良好的线性关系:-lgk=0.5215σ+1.326;-lgk=0.8271[(σ_m+σ_p)/2]⁺1.506.