Thiol-ene chemistry as an effective tool for hydrophobization of cotton fabrics

In this paper, several methods of hydrophobization of cotton fabrics using the thio-ene click reaction were compared. Durable, superhydrophobic textiles were obtained in an easy way. Various variants of functionalized silsesquioxanes were used for the hydrophobization of fabrics. The synthesis of bifunctional silsesquioxanes (RSiMe₂O)₄(ViSiMe₂O)₄Si₈O₁₂ and (RSiMe₂O)₄(R’SiMe₂O)₄Si₈O₁₂ were performed via hydrothiolation of silsesquioxane derivative (ViSiMe₂O)₈Si₈O₁₂. Alkoxysilyl, alkyl and fluoroalkyl moieties were introduced as functional groups. Samples were prepared using four methods, differing in the modification method and the number of stages. During the research, fabrics were modified via (a) the dip-coating process, (b) carrying out thiol-ene click reactions directly on the surface of the fabric and (c) using both of these methods. The hydrophobicity of the fabric was evaluated by measuring the Water contact angle (WCA). The obtained samples were also examined using infrared analysis (FT-IR), Scanning electron microscope (SEM), and Elemental analysis (SEM–EDS). All analyses were performed before and after the washing process in order to verify the stability of the performed modifications.

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Plasma enhanced aerosol–gel method: a new way of preparing ceramic coatings

The sol–gel process is widely used for the production of powders, coatings and bulk materials. However, being a wet-chemical technique, it has certain limitations related to properties of aqueous colloidal solution, especially when applied as a coating. The most frequently used methods, such as dip- and spin-coating, are difficult to apply onto more complex substrates. In these cases, the aerosol–gel deposition method can be regarded as the solution of this problem. In the present article, a novel plasma enhanced aerosol–gel method of coatings production is presented. A novelty of this method is based on an integration of the aerosol–gel deposition of thin films and their low temperature plasma treatment. Owing to the above, all stages of the coatings production process—substrate preparation, film deposition, and its plasma treatment, can be carried out in a single reactor. The design and operational scheme of such device is presented in this work. Using this device, thin coatings were first deposited on substrates and then plasma treated. The effect of deposition and plasma discharge conditions on morphology and chemical structure of the films has been studied. It was found that plasma treatment had a substantial influence on all the examined properties of the aerosol–gel deposited coatings.     

The synthesis and characterisation of some nickel(0) complexes with π-bounded vinylsilicon ligands; the molecular structure of [Ni{P(C6H5)3}2{η-CH2CHSi(CH3)3}]

Reactions of the nickel(0) complexes [Ni(cod)₂] (in the presence of PP or [Ni(PPh₃)₂C₂H₄] with vinyl-siloxanes, -silanes or -silazanes yield, by displacement of alkene ligand, the new nickel π-complexes [Ni(PPh₃)₂(η-CH₂CHSi(OSiMe₃)₃)] (2), [{Ni(PPh₃)}₂{μ-(η-{(CH₂CH)₂SiMe}₂O})] (4), [Ni(PPh₃){η⁴-CH₂CHSi(Me)(μ-O)}₃] (5), [{Ni(η-CH₂CHSiMe₂)₂O}(η-CH₂CHSiMe₃)] (7) and the known complexes [Ni(PPh₃)₂(η-CH₂CHSiMe₃)] (1), [{Ni(PPh₃)}₂{μ-(η-(CH₂CH)₄Si})] (3), [{Ni(PPh₃)(η-CH₂CHSiMe₂)₂NH}] (6) obtained by a simple one pot synthesis, more efficiently than in hitherto published reports. The X-ray crystal structure of (1) shows a trigonal planar environment around the nickel atom.     

Synthesis of organofunctional silanes with sterically hindered substituents at silicon atoms

Organofunctional silanes with more sterically hindered substituents at the silicon atom than the typical methoxy (ethoxy) group have lately been frequently used as silane coupling agents, in polymer coupling systems, sol‐gel processes and also as interpenetrating polymer network substrates. New and very efficient synthetic ways leading to organofunctional silanes of the above type with methacryl, amine, chloro and isocyanato functional groups are proposed here. Catalytic transesterification and/or alcoholysis of chloropropyltrialkoxysilanes followed by­nucleophilic substitution has been employed. Copyright © 2001 John Wiley & Sons, Ltd.     

Stereoelectronic effects of substituents at silicon on the hydrosilylation of 1-hexene catalysed by [RhCl(cod)(1-hexene)]

Summary Trisubstituted silanes, HSiR_3-n X _n (R = Me or Et, X = Cl, OEt, or Ph; n = 0–3) oxidatively add to the complex [RhCl(cod)(1-hexene)] (cod = cycloocta-1,5-diene) to yield [RhCl(cod)(1-hexene)(H)(SiR₃)] [(1)]. Subsequent steps of hydrosilylation follow, i.e. cis-insertion of the alkene (- rearrangement) and then reductive elimination of the product, according to the general Chalk and Harrod scheme. A quantitative correlation between the second order rate constant, k ₁, of the oxidative addition (followed spectrophotometrically) at 20°C in benzene solution and the structure of the trisubstituted silane represented by Stereoelectronic parameters , and E' for the SiR_3-n X _n groups was established. The maximal hydrosilylation rate followed by g.l.c., is strongly retarded by highly electronegative substituents X on silicon and results from the elimination rate of the hydrosilylation product from (1) and the maximal concentration of (1) in solution.Dedicated to Professor K. Rühlmann on the occasion of his 65th birthday. Part XXVII in the series Catalysis of Hydrosilylation; for Part XXVI see Polish J. Appl. Chem., 38, 169 (1994).     

On-column derivatization with o-phthaldialdehyde for fast determination of homocysteine in human urine

A new assay for urinary homocysteine is described. The assay relies on an on-column derivatization with o-phthaldialdehyde, using a reversed-phase HPLC column and detection/quantification by fluorescence. The analysis time for reduced and total homocysteine, including sample work-up, was 5 and 13 min, respectively. Quantification limit was 25 nM.     

Mechanism of the condensation of homocysteine thiolactone with aldehydes

Chemical reactivity of homocysteine thiolactone (HTL) has been implicated in cardiovascular disease. Owing to its aminoacyl-thioester character, HTL undergoes facile electrophilic and nucleophilic reactions at its amino and activated-carboxyl group, respectively. To gain insight into the mechanism of the reactions involving its amino group, the kinetics of the condensation of homocysteine thiolactone with formaldehyde, acetaldehyde, and pyridoxal phosphate, were analyzed in the pH range from 5 to 10. The reactions were first order with respect to HTL, aldehyde, and hydroxide ion concentrations. Of the two ionic species of HTL (pKa=6.67+/-0.05), the acid form HTL+ was approximately 100-fold more reactive than the base form HTL(0). The reactions of HTL with aldehydes involve intermediate adducts. The conversion of the intermediate carbinolamine to a product, 1,3-tetrahydrothiazine-4-carboxylic acid or its 2-substituted analogue, occurs in a two-step reaction. The first step involves hydrolysis of the thioester bond in the intermediate, facilitated by anchimeric assistance by the oxygen of the carbinolamine group of the intermediate. The second step involves an attack of the liberated thiolate on the aldehyde-derived carbon of the intermediate, affording 1,3-tetrahydrothiazine-4-carboxylic acid or its 2-substituted analogue. An unusual feature of these reactions is that the formation of the carbinolamine group increases the reactivity of the thioester bond of HTL approximately 10(4)-fold. The facile formation of tetrahydrothiazines may contribute to HTL elimination from the human body.     

A quantitative approach to dynamic and isothermal curing of an epoxy resin modified with oligomeric siloxanes

Journal of Thermal Analysis and Calorimetry - The reactivity of a system comprising commercial epoxy resin Epidian® 6 (E6) and triethylenetetramine (Z-1) hardener was studied. The system was...     

Cation exchange HPLC analysis of desmosines in elastin hydrolysates

Desmosine crosslinks are responsible for the elastic properties of connective tissues in lungs and cardiovascular system and are often compromised in disease states. We developed a new, fast, and simple cation exchange HPLC assay for the analysis of desmosine and isodesmosine in animal elastin. The method was validated by determining linearity, accuracy, precision, and desmosines stability and was applied to measure levels of desmosines in porcine and murine organs. The detection and quantification limits were 2 and 4 pmol, respectively. The run-time was 8 min. Our cation exchange column does not separate desmosine and isodesmosine, but their level can be quantified from absorbance at different wavelengths. Using this assay, we found that desmosines levels were significantly lower in elastin isolated from various organs of immunodeficient severe combined immunodeficiency mice compared with wild-type animals. We also found that desmosines levels were lower in lung elastin isolated from hyperhomocysteinemic Pcft ^−/− mice deficient in intestinal folate transport compared with wild-type Pcft ^+/+ animals.     

Preparation and characterisation of monolayers and Langmuir–Blodgett films of liquid crystal mixed with cubic silsesquioxanes

Polyhedral oligomeric silesquioxanes (POSS) with eight polyether substituents were mixed with the liquid crystal (LC) 4-octyloxy-4′-cyanobiphenyl and spread at the air/water interface. The surface pressure-area and surface potential-area isotherms were recorded for different weight ratios of both components. The obtained results showed that POSS molecules had beneficial influence on LC monolayer improving its stability and rigidity. Moreover, it was found that some LC–POSS mixtures collapse reversibly and form multilayer films on the top of LC monolayer. On the other hand, interfacial dilatational and shear rheology indicated decrease of elasticity of the films after mixing. Brewster angle microscopy revealed multilayer structure of the condensed film and formation of net-like structures in the expanded film. These films were successfully transferred on solid substrates using the Langmuir–Blodgett technique. The scanning electron microscopy images confirmed the film deposition and formation of networks by POSS–LC mixtures. These findings may be useful in the fabrication of electronic devices based on LCs.