Unusual Intercalation of Cationic Smectite Clays with Detergent‐Ranged Carboxylic Ions

Summary: The organic intercalation of cationic smectite clays is achieved by using alkali salts of alkyl carboxylic acids, instead of using conventional quaternary ammonium salts as ionic exchanging agents. Various organic acid salts, such as CH₃(CH₂)₁₆COO⁻Na⁺, can be incorporated into divalent montmorillonite (M²⁺‐MMT) with a 30–40 wt.‐% organic embedding and an X‐ray diffraction basal spacing of 43 Å from the pristine 10 Å. The intercalation is generalized for carboxylate salts of different alkyl lengths and for alkali metal ions, including sodium and potassium ions, but is specific for the divalent MMT clay. This new type of organic species for clay modification allows the preparation of organoclays in the absence of quaternary ammonium salts. It is proposed that the organic embedding is driven by the formation of a thermodynamically stable RCOO⁻/M²⁺/SiO⁻ complex.

Graphical illustration of the carboxylic acid salt complex with the divalent cations on silicate K10.     

Ethylene‐Norbornene Copolymerization by New Titanium Complexes Bearing Tridentate Ligands. Sidearm Effects on Catalytic Activity

The Ti complexes containing tridentate [O⁻NS^R] (R = Me, ⁱPr) ligands with alkylthio sidearms were prepared. The methylthio ether complex (R = Me shown in the Scheme) exhibits an excellent activity for copolymerization of ethylene with norbornene upon activation with MMAO, which is 10 times more active than the corresponding phenylthio one (R = Ph).

     

Spontaneous Ring‐Opening Polymerization of Macrocyclic Aromatic Thioether Ketones under Transient High‐Temperature Conditions

Summary: Spontaneous ring‐opening polymerization of macrocyclic aromatic thioether ketones [ 1,4‐SC₆H₄COC₆H₄ ]_n (n = 3 and 4), in which the thioether linkages are para to the ketone, occurs during rapid, transient heating to 480 °C, to afford a soluble, semi‐crystalline poly(thioether ketone) of high molar mass (η_inh > 1.0 dL · g⁻¹). Corresponding macrocyclic ether ketones, and a macrocyclic thioether ether ketone in which the thioether linkage is para to the ether rather than to the ketone, show no evidence of polymerization under analogous conditions.

The uncatalysed ring‐opening polymerization of macrocycle 1 , within the pores of an alumina microfiltration membrane, leads to formation of polymer 3 with the microstructure shown in the above scanning electron micrograph.     

Determination of the composition and the stability constants of complexes of silver(I) with some sulphur containing pyridines a potentiometric investigation

A series of sulphide-containing pyridines of general formula ? (CH₂)_x? S? R where R = CH₃, C₂H₅, CH₂CH₂OH and x = 1, 2 has been prepared and studied potentiometrically in the presence of Ag⁺ in 0.5 M (K)NO₃ medium at 25°C. The complex formation is discussed in terms of the Taft σ*-parameters for the substituents. In acid region, where the complexes AgLH²⁺ and AgL₂H₂³⁺ were formed, coordination occurs through the thioether group. In neutral and alkaline medium their was evidence for the species AgL₂H²⁺, AgL⁺, AgL₂⁺, Ag₂L₂²⁺ and Ag₂L²⁺ in which Ag⁺? S and Ag⁺? bonds are involved. The five membered chelate rings for the AgL⁺ and AgL²⁺ species are found to be more stable than the six-membered ones.     

Polymerization of butadiene initiated by the 1:1 chelate of n-butyllithium and N,N,N′,N′-tetramethylethylenediamine

Evidence is given for the species involved in the initiation and propagation steps in the polymerization of butadiene with n-butyl lithium: tetramethylethylene diamine (TMEDA) as being the monomeric butyl lithium and the solvated ion pair, (A), respectively. Species A is also produced on the metalation of polybutadiene with butyl lithium: TMEDA.     

An evaluation of the kinetic parameters for the reaction of trifluoromethyl radicals with CH3Cl in the gas phase in the temperature range from 416 to 636 K

The hydrogen and chlorine atom abstraction reactions from CH₃Cl by CF₃ radicals produced by the photolysis of hexafluoroacetone (HFA) and CF₃I were studied relative to the recombination of CF3 radicals (I) The Arrhenius parameters obtained in the temperature range 416 to 578 K are: where Θ = 2,303.RT cal mol^?1 and k₂ is the recombination rate constant for the CF₃ radicals. The factors that influence the transfer processes of chlorine and hydrogen are analyzed in a series of reactions of halomethanes with CF₃ and CH₃ radicals. © 1993 John Wiley & Sons, Inc.     

Chlorine Dioxide as an Electron-Transfer Oxidant of Olefins. Preliminary Communication

The kinetics and product studies of oxidation of eight olefins 1 - 8 by ClO₂ in H₂O in the pH range 3-7 are described. The reaction is faster as the pH decreases. At pH < 4, ClO₂ reacts equimolarly with olefins to yield isomeric mixtures of chlorohydrines and 1,2-dioxygenated products, following the equation: The order of reactivity is: (E)-stilbene > indene > β-methylstyrene > acenaphthylene > α-methylstyrene > styrene > cyclohexene > allylbenzene. A multi-stage radical-cation mechanism is proposed, in which an initial reversible protonation: is followed by an electron-transfer stage (rate-determining): The cation-radical thus produced, adds rapidly an additional ClO₂ to form dioxygenated products. The chlorohydrines most likely arise from HClO additions to the olefinic double bonds, which, in turn, generate from dismutation of 2 HClO₂ into HClO + H⁺ + ClO.     

Crystalline Complex of Syndiotactic Polystyrene with Poly(ethylene Glycol) Dimethyl Ethers

It has been clarified that syndiotactic polystyrene (sPS) forms co‐crystalline structures with polyethylene glycol dimethyl ethers (PEGDMEs) with molecular weights ranging from 178 to 1 000 g · mol⁻¹ through a guest exchange procedure assisted by a plasticizing agent. The PEGDME molecules are incorporated into the spaces between sPS polymer sheets consisting of (T₂G₂)₂ helices. The results of X‐ray diffraction and gravimetric measurements suggest that one or less molecules are included per unit cell for PEGDME with average molecular weight of 1 000 g · mol⁻¹, which indicates the possibility that longer polymeric molecules can be introduced into sPS lattices with multiple site occupation.

     

Step‐Growth Radical Addition‐Coupling Polymerization (RACP) for Synthesis of Alternating Copolymers

We report a new type of step‐growth radical addition‐coupling polymerization (RACP) involving consecutive addition of carbon‐centered radical derived from α,α′‐dibromo dibasic ester to NO double bond of C‐nitroso compound followed by cross‐coupling of carbon‐centered radical and in situ formed nitroxyl radical, which produces alternating copolymers with high molecular weight and unimodal molecular weight distribution from saturated and unsaturated monomers.

     

Structural Characterization of Biocidal Oligoguanidines

Oligomeric guanidines can be obtained by polycondensation of guanidine hydrochloride and 1,2‐bis(2‐aminoethoxy)ethane. A comparative MALDI‐TOF mass spectrometry/NMR spectroscopy study with a ¹³C‐labeled sample enabled the unambiguous analysis of a guanidine‐based polymer. Among the four major product series unprecedented macrocyclic compounds were detected. The minimum inhibition concentrations for four different microorganisms were determined, showing excellent biocidal activities.

     

Über das Auftreten von Polysulfan-diphosphonaten bei der Umsetzung von Monothiophosphat mit Disulfan-diphosphonat

On the Formation of Polysulphane Diphosphonates by the Reaction of Monothiophosphonate with Disulphane Diphosphonate In acid solution SPO reacts with S₂P₂O forming higher polysulphane diphosphonates. The formation of S₃P₂O and S₄P₂O is proved by evaluation of the double labelling with ³⁵S? ³²P after high paper electrophoresis.     

Amphiphilic Poly(4‐acryloylmorpholine)/Poly[2‐(N‐carbazolyl)ethyl acrylate] Random and Block Copolymers Synthesized by NMP

A series of random copolymers and block copolymers containing water‐soluble 4AM and fluorescent VAK are synthesized by NMP. The homopolymerizations of 4AM and VAK and 4AM/VAK random copolymerization are performed in 50 wt% DMF using 10 mol% SG1, resulting in a linear increase in versus conversion, and final polymers with narrow molecular weight distributions ( < 1.4). Reactivity ratios r_VAK = 0.64 ± 0.52 and r_4AM = 0.86 ± 0.66 are obtained for the 4AM/VAK random copolymerization. In addition, a poly(4AM) macroinitiator is used to initiate a surfactant‐free suspension polymerization of VAK. After 2.5 h, the resulting amphiphilic block copolymer has = 12.6 kg · mol^?1, = 1.48, molar composition F_VAK = 0.38 with latex particle sizes between 270 and 475 nm.

     

Neuartige massenspektrometrische Zerfallsreaktionen bei α,ω-disubstituierten Alkanen. 15. Mitteilung über das massenspektrometrische verhalten von stickstoffverbindungen [1]

The mass spectral behaviour of α,ω-disubstituted alkanes and, especially, that of different N-substituted α,ω-diaminoalkanes has been investigated. It was found that the two amino groups which are separated by CH₂-groups can fragment only to a small extent indepently from each other. Yet those fragmentation reactions are predominant in which both functional groups participate. The main reactions of this type are:

• 1 Loss of the N-substituent (R) from the molecular ion, leading to the [M⁺—R]-ions.
• 2 Loss of NH₃, primary or secondary amines from the [M⁺—R]-ion in the case of monodi-, tri- and tetra-substituted diamino compounds respectively.
• 3 α-Cleavage to the non charged nitrogen atom by forming the ions
• 4 S_Ni-type fragmentation.

The mechanisms of these fragmentation patterns were deduced by using D-labelled derivatives, from metastabile peaks and high resolution mass spectrometry. These reactions seem to be typical for disubstituted alkanes.     

Synthesis of Amphiphilic Supramolecular Miktoarm Star Copolymers by Molecular Recognition

Synthesis of novel amphiphilic supramolecular miktoarm star copolymers has been achieved through complementary molecular recognition and interactions between carboxy groups and amino groups. Polystyrenes carrying two and one carboxy groups at the middle of the polymer chain are used as precursors to react with poly(ethylene oxide) (PEO) end‐capped with a primary amine functionality (–NH₂) or a quaternary ammonium hydroxide functionality (–N⁺(CH₂CH₃)₃OH⁻). The result suggests that the basicity of the amine plays a key role in the molecular recognition procedure. The efficiency of ionic bond formation can be enhanced from 40% up to 97% by using PEO‐N⁺(CH₂CH₃)₃OH⁻ instead of PEO‐NH₂. The obtained supramolecular polymers can be dissociated in dilute acid solution at room temperature.

     

Zur Darstellung von Cyclophosphaten,Cyclophosphatophosphonaten, Diphosphonaten und Diphosphiten in Harnstoffschmelzen

Preparation of Cyclophosphates, Cyclophosphatophosphonates, Diphosphonates, and Di-phosphites in Urea Melts Ammonium cyclotriphosphate (NH₄)P₃O₉, ammonium cyclotetraphosphate [P^IV? P^IV ? O? ]₂, ammonium cyclotriphosphatophosphonates Ammonium organyldiphosphonates And ammonium diphosphites are prepared in high yields on heating acidic phosphates, phosphonates, and phosphites in urea or urea/ammonium nitrate melts. The mechanism of the dehydration of phosphorus compounds containing POH groups in molten urea is discussed.     

Preparation of Crosslinked Chitosan/Silk Fibroin Blend Films for Drug Delivery System

Crosslinked chitosan/silk fibroin blend films were prepared by a solution casting technique using glutaraldehyde as crosslinking agent. Drug release characteristics of the blend films with various blend compositions were investigated. Theophylline, diclofenac sodium, amoxicillin trihydrate, and salicylic acid were used as model drugs. The release studies were performed at 37 °C in buffer solutions at pH 2.0, 5.5, and 7.2. It was found that the blend films with 80% chitosan content showed the maximum amount of model drug release at pH 2.0 for all the drugs studied here. This result corresponded to the swelling ability of the blend films. From a swelling study, the maximum degrees of swelling of the drug‐loaded blend films were obtained at this pH and blend composition. The amount of drugs released from the films with 80% chitosan content, from the highest to the lowest values, occurred in the following sequence: salicylic acid > theophylline > diclofenac sodium > amoxicillin.

Comparison of the amounts of drug released from chitosan and the blend film with 80% chitosan content at pH 2.0: (filled) chitosan film, and (blank) blend film with 80% chitosan content (SAL = salicylic acid, THEO = theophylline, DFS = diclofenac sodium, AMX = amoxicillin).     

Development of Nanodomain and Fractal Morphologies in Solvent Annealed Block Copolymer Thin Films

We have systematically studied the thin film morphologies of asymmetric polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) diblock copolymer subjected to solvent vapors of varying selectivity for the constituent blocks. Upon a short treatment in neutral or PS‐selective vapor, the film exhibited a highly ordered array of hexagonally packed, cylindrical microdomains. In the case of PEO selective vapor annealing, such ordered cylindrical microdomains were not obtained. Instead, fractal patterns on the microscale were observed and their growth processes investigated. Furthermore, hierarchical structures could be obtained if the fractal pattern was exposed to neutral or PS selective vapor.

     

The oxidation of diethylhydroxylamine by nitrogen dioxide

Diethylhydroxylamine, (C₂H₅)₂NOH, was oxidized by NO₂ at 25°C in a long-path-length infrared gas cell. The measured products of the reaction were HONO and CH₃CHO. The reaction scheme which explains the reaction is was oxidized by NO₂, and the reaction was found to be very rapid with k₁ > 10^?16 cm³/s. The products of the reaction were verified by both infrared absorption (CH₃CHO, C₂H₅NO) and gas chromatography (CH₃CHO, NO).     

Ab-initioMRD–CI calculations on a C?NO2 decomposition pathway of nitrobenzene

To study molecular decomposition pathways it is necessary to use ab initio multireference determinant–configuration interaction or MCSCF (multiconfiguration SCF ) calculations. The MRD –CI (multireference double excitation–configuration interaction technique of Buenker and Peyerimhoff) calculations on the decomposition pathway of nitrobenzene were carried out using all of the occupied molecular orbitals in the region of the bond being dissociated, plus all of the virtual orbitals. An effective CI Hamiltonian was used into which were folded the effects of all of the occupied molecular orbitals from which excitations were not allowed. So far we have investigated the lowest ¹A₁, ³A₁, ¹A₂, ³A₂, ¹B₁, ³B₁, ¹B₂, ³B₂ states and are investigating the higher states. Our results show a wealth of structure in the potential energy surfaces for the various electronic states of nitrobenzene as a function of distance. A number of the states are predissociative and change dominant configuration one or more times along these potential energy surfaces.     

Metal‐Free Activation in the Anionic Ring‐Opening Polymerization of Cyclopropane Derivatives

The successful activation observed when using Bu^tP₄ phosphazene base and thiophenol or bisthiols for the anionic ring opening polymerization (ROP) of di‐n‐propyl cyclopropane‐1,1‐dicarboxylate is described. Well‐defined monofunctional or difunctional polymers with a very narrow molecular weight distribution were obtained through a living process. Quantitative end‐capping of the propagating malonate carbanion was accessible by using either an electrophilic reagent such as allyl bromide or a strong acid such as HCl. Kinetics studies demonstrated a much higher reactivity compared to the conventional route using alkali metal thiophenolates.