Chemistry and application of organic isocyanates,IX. Conversion of tolylene-2,4-diisocyanate into urethane derivatives by means of heptane-1,4,7-triol

Investigations on the conversion of tolylene-2,4-diisocyanate (2,4-TDI or TDI) with heptane-1,4,7-triol 1,4,7-HPT or HPT) at 55–85°C and various molar ratios of starting materials are described. By means of mass spectroscopic analysis and gel permeation chromatography, molecular weights of six oligomers and their percent contents in the products have been estimated. Moreover, a scheme of the formation of all prepared isocyanate prepolymers has been proposed. It has been shown, that apart from oligomers having the structures resulting from the reaction of 1,4,7-HPT with the isocyanate group in the position “4”, reaction products contained oligomers, which confirmed the reactivity of isocyanate group in the position “2”, too.     

Theoretical reactivity of tolylene-2,4-diisocyanate and tolylene-2,6-diisocyanate,and structures of oligomers contained in the products of conversion of tolylene-2,4-diisocyanate into urethane and biuret derivatives

By the methods of quantum chemistry it is possible to calculate a number of theoretical quantities dependant on the structure of chemical compounds. In this paper quantum chemical calculations have been done in order to explain quantitatively the differences in the reactivity of isocyanate groups in tolylene diisocyanates and for the account of directions of oligomer formation with definite structures. These quantities have been connected in a simple way with the chemical reactivity of the molecules. The results of calculations made with the INDO semiempirical method are in a very good correlation with results of experimental investigations.     

Urethanes. I. Organometallic catalysis of the reaction of alcohols with isocyanates

The catalysis of the reaction of n-butyl alcohol with isocyanates, using organometallic derivatives of lead, tin, and mercury, has been investigated. The rate of the reaction was measured by following the disappearance of the isocyanate absorption in the infrared. Phenyl, n-butyl, and cyclohexyl isocyanate were chosen to represent typical aromatic primary and secondary aliphatic isocyanates. Within the same series of catalysts, R_nMOAc, the catalytic effect decreases in the order RHg > R₃Sn > R₃Pb; and in all cases R = aryl > R = alkyl. The electronic effects of substituents on the aryl moiety are not pronounced. Changes in X of R_nMX greatly affect the catalytic activity. The mechanism of organometallic catalysis of the alcohol-isocyanate reaction occurs via a template-type mechanism whereby the catalyst acts to complex both reactants in a catalyst phase allowing the reaction to occur with greater facility.     

Chemistry and application of organic isocyanates IV. Conversion of hexamethylene diisocyanate into biuret derivatives by means of Na2SO4 · 10 H2O

The attempts of hexamethylene diisocyanate (HDI) conversion by means of Na₂SO₄ · 10 H₂O at 120°C to 160°C at different molar ratios of reactions of reactants have been described. It has been shown that in this process apart form N,N′,N″-tris(6-isocyanatohexyl)biuret there are also formed biuret derivatives of higher molecular weight. Due to the application of mass spectrometry analyses and gel permeation chromatography the scheme of formation of prepolymers having the biuret structure of molecular weight up to 1300 has been proposed.     

Diffusion Studies of Glucose and Sucrose in Chitosan Membranes and Beads for Enzymatic Production Processes

The diffusion of glucose and sucrose was investigated in membrane and bead experiments. Concentration‐dependent diffusion coefficients of pure glucose and sucrose were determined in precipitated chitosan membranes of varying thickness using diffusion cell experiments. Contrary to fructose, the resulting diffusion coefficients of glucose and sucrose did not reach their free diffusion coefficients at infinite dilution suggesting additional interactions between chitosan and these two sugars. Counter‐diffusion in bead experiments showed a good agreement between predicted and measured data allowing the inclusion of the diffusion data in the simulation of the proposed production process for laminaribiose. In conclusion, the encapsulation in chitosan presented a good trade‐off between increased mass transfer resistance as evaluated by the Thiele modulus and improved thermal stability and antibacterial activity.     

新时期高分子化学的发展及应用探析

高分子是化学科学的重要组成部分,人类最开始主要是利用和接触天然高分子材料,但是随着社会的进步和经济水平的提高,化学的研究进入了一个崭新的阶段。新时期的高分子化学技术广泛应用于人们生活各个方面。基于此,主要研究新时期高分子化学的发展及应用。     

Chemistry and application of organic isocyanates V. Conversion of 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane into urea and biuret derivatives by means of Na2SO4 · 10H2O

Under different conditions of reaction the conversion of 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane into urea and biuret derivatives was carried out applying water as the converting agent. It has been proved that reaction products are heterogeneous, since four oligomers are contained in the mixtures. The influence of the reaction conditions on the concentration of the components was investigated. The results of physico-chemical measurements of the obtained products in dependence on the temperature of synthesis and applied molar ratio of the reagents have been interpreted.     

Functional polymers for colloidal application. VI. Syntheses and dispersing ability of lipomodified naphthalenesulfonate formaldehyde condensates

Butyl-substituted naphthalenesulfonate formaldehyde condensates (C4NSF) with different molecular weights were synthesized. The structures were confirmed by NMR in terms of the appearance of the signal at δ = 3.3–4.0 ppm, and the molecular weights of the synthesized C4NSFs were compared by gel permeation chromatography (GPC). C4NSFs used as dispersants were compared to unmodified naphthalenesulfonate formaldehyde condensates (NSF) in their ability to disperse nonpolar particles (carbon black) and polar particles (TiO₂) in water. Their dispersing ability was evaluated by both a viscosity method and a microscopy method. For dispersing carbon black in water, it was found that using C4NSFs as dispersing agents results in a lower viscosity, a lower yield value by the viscosity method, and a more homogeneous dispersion of particles as determined by microscopy. These results indicate that the butyl group enhances the dispersing ability of C4NSF. The effect of the butyl group on the dispersing ability of C4NSF was interpreted by the results of the measured adsorption amount that was also enhanced by the existence of the butyl group. For dispersing TiO₂ in water, C4NSF results in a higher viscosity and a higher adsorption amount of the dispersed system than NSF. These phenomena were interpreted in terms of the hydrophobic interaction between the butyl groups and the bridging effect. © 1993 John Wiley & Sons, Inc.     

Catalysis of the reaction between isocyanates and protonic substrates. I. Metal salt–amine complexes as catalysts in the polyurea foaming process

Tertiary amines and metal [Cu(II), Zn(II)] salts exhibit a synergistic effect in the catalysis of the isocyanate water reaction. The amino complexes of zinc and copper salts display a very large versatility in defining the most suitable formulations for the polyurea foam production. The foaming process is indeed controlled by the nature and the composition of these new catalytic combinations; kinetics of foaming and textural characteristics of final foams are easily modified in that way.     

Syntheses and reactions of photopolymers,I. New photosensitive azo monomers,photolysis, interfacial polycondensation,viscosity measurements,photodegradation

The synthesis of new, unsymmetrically functionalized azo compounds and their incorporation into polymers is described. Their photochemical decomposition and thermal stability was studied by UV spectroscopy and differential scanning calorimetry (DSC), respectively. Chemical degradation was followed by viscosity measurements.     

Syntheses of Polypeptides and Their Biomedical Application for Anti-Tumor Drug Delivery

Polypeptides have attracted considerable attention in recent decades due to their inherent biodegradability and biocompatibility. This mini-review focuses on various ways to synthesize polypeptides, as well as on their biomedical applications as anti-tumor drug carriers over the past five years. Various approaches to preparing polypeptides are summarized, including solid phase peptide synthesis, recombinant DNA techniques, and the polymerization of activated amino acid monomers. More details on the polymerization of specifically activated amino acid monomers, such as amino acid N-carboxyanhydrides (NCAs), amino acid N-thiocarboxyanhydrides (NTAs), and N-phenoxycarbonyl amino acids (NPCs), are introduced. Some stimuli-responsive polypeptide-based drug delivery systems that can undergo different transitions, including stability, surface, and size transition, to realize a better anti-tumor effect, are elaborated upon. Finally, the challenges and opportunities in this field are briefly discussed.     

有机科研用试剂的研发与应用

综述了科研用化学试剂研发平台已获得的研发产品糖衍生物、手性试剂、芳杂环、金属有机化合物、材料单体和其他有机合成中间体等高端试剂的研究简况与应用情况,概述了研发试剂的质量控制体系建设.阐明了该平台建立的意义,说明高端试剂研发平台的建立对我国多个领域科研工作起到有效的支撑作用.     

Flame-retarding materials—I. Syntheses and flame-retarding property of alkylphosphate-type polyols and corresponding polyurethanes

In this research, oligomeric polyalkyl phosphate-type polyols (P% = 14–17) were synthesized from ethylene glycol or 1,4-butanediol (PBE or PBB) by means of butyl phosphorodichloridate, which was prepared from phosphorus oxychloride and butanol. These polyols were then reacted with isocyanate to form the corresponding polyurethanes (PETD and PBTD). These polyols were characterized by FTIR, ¹H-NMR, and ³¹P-NMR, and the thermal stabililties were measured by thermogravimetry analysis. The degradation phenomena were traced by FTIR and interpreted in terms of the degradation and formation of bonds. The corresponding polyurethanes were also characterized by FTIR and ¹H-NMR, and their thermal stability was also studied by thermogravimetry analysis. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1635–1643, 1998     

阻垢剂的合成及应用研究进展

阐述了阻垢剂的种类、性能及研究应用现状,其中聚环氧琥珀酸和聚天冬氨酸两大类新型绿色阻垢剂成为近几年国内外的研究热点.并指出今后的工作重点和发展方向.     

Electrochemical test methods for evaluating organic coatings on metals: an update. Part I. Introduction and generalities regarding electrochemical testing of organic coatings

The status of evaluating organic coated metals utilizing electrochemical means was reviewed for the period of 1988–1994. The general improvements in the overall technology are presented in three sections. Part I covers the test cell configurations, changes in testing approaches and a brief survey of measurement equipment. Part II presents the test methods involving a single test parameter such as the panel potential relative to a reference electrode, electrochemical voltage and/or current noise, as well as the dc resistance of the coating on the metal substrate. Multiple test parameter measurements such as potentiodynamic curves and electrochemical impedance spectroscopy are covered in Part III. Although the majority of data were taken from the literature, some supplementary data are included from NSWCCD studies.     

Hydroperoxidation of organic compounds at the LIQUID/GAS interface I. Apparatus and method

A new method and apparatus are described for hydroperoxidation of organic compounds at the liquid/gas interface which is formed in a spirally curved tube. The energy required for stirring is removed, although extra energy is required for the compressors to enable the gas to provide the necessary agitation. The reaction rate should be higher than that in methods used at present.     

New organic polymers,I. Synthesis and characterization of poly Schiff bases from benzidine-3,3′-dicarboxylic acid

Thermally stable and semiconducting polymers are synthesized by condensing benzidine-3,3′-dicarboxylic acid (BDC), with dicarbonyl compounds like glyoxal, cyclohexane-1,4-dione, 4,4′-diacetyl diphenyl ether and benzil under different experimental conditions. These poly Schiff bases are insoluble in common organic solvents. They are characterized by IR- and viscosity studies, thermal analysis, and the study of electrical properties at various temperatures. Variation of the electrical conductivity, σ, with temperature was found to confirm with the empirical relation: