Chelate polymers: II. Some novel transition metals complexes with azomethine‐containing siloxanes and their polyesters

New Schiff bases of 2,4‐dihydroxybenzaldehyde with siloxane‐α,ω‐diamines having different numbers of siloxane units in the chain have been synthesized and characterized by spectroscopy, elemental and thermal analyses. These azomethines were found to form complexes readily with copper(II), nickel(II), cobalt(II), cadmium(II) and zinc(II). From IR and UV–Vis studies, the phenolic oxygen and imine nitrogen of the ligand were found to be the coordination sites. Thermogravimetric analysis (TGA) data indicate the chelates to be more stable than the corresponding ligands. The melting points increase with shortening of the siloxane segment from azomethine, as well as the result of complexation. The chelates obtained were covalently inserted in polymeric linear structures by polycondensation through the OH‐difunctionalized ligand with 1,3‐bis(carboxypropyl)tetramethyldisiloxane. Direct polycondensation, assisted either by acetic anhydride or N,N′‐dicyclohexylcarbodiimide as dehydrating agent and the complex 4‐(dimethylamino)pyridinium 4‐toluenesulfonate as catalyst, was used for the synthesis of these compound types. The structures of the polymers obtained were confirmed by IR, UV and ¹H NMR. Characterization was undertaken by TGA, solubility tests and viscosity measurements. Copyright © 2003 John Wiley & Sons, Ltd.     

Polysiloxanol condensation and disproportionation in the presence of a superacid

Kinetics studies of the condensation of model hydroxyl-terminated oligosiloxanes, pentamethyldisiloxane-1-ol (MDH) and heptamethyltrisiloxane-1-ol (MD₂H), catalysed by protic complex of tetrakis(pentafluorophenyl)borate in the toluene solution were performed. The dominating reaction was condensation, which was accompanied by disproportionation of oligosiloxanols. Water released in the condensation forms separate dispersed phase, but the phase separation and the presence of water does not affect the rate of the polycondensation. Both processes, condensation and disproportionation, show analogous kinetic laws being first order in silanol and half order in catalyst. They exhibit also similar values of activation parameters. The kinetics are explained by the formation of a reactive protic complex of silanol with borate being in fast preequilibrium with an unreactive complex including two borate molecules and the silanol molecules. The equilibrium lies to the side of the unreactive borate complex.     

Synthesis and characterization of wholly aromatic poly(azomethine)s containing donor–acceptor triphenylamine moieties

N‐(4‐nitrophenyl)‐4′,4″‐bisformyl‐diphenylamine was synthesized from N‐(4‐nitrophenyl)‐diphenylamine by the Vilsmeier‐Haack reaction. Soluble aromatic poly(azomethine)s (PAMs) were prepared by the solution polycondensation of N‐(4‐nitrophenyl)‐4′,4″‐bisformyl‐diphenylamine and aromatic diamine in N‐methyl‐2‐pyrrolidone (NMP) at room temperature under reduced pressure. All the PAMs are highly soluble in various organic solvents, such as N,N‐dimethylacetamide (DMAc), chloroform (CHCl₃), and tetrahydrofuran (THF). Differential scanning calorimetry (DSC) indicated that these PAMs had glass‐transition temperatures (T_gs) in the range of 170–230 °C, and a 10% weight‐loss temperatures in excess of 490 °C with char yield at 800 °C in nitrogen higher than 60%. These PAMs in NMP solution showed UV‐Vis charge‐transfer (CT) absorption at 405–421 nm and photoluminescence peaks around 462–466 nm with fluorescence quantum efficiency (Φ_F) 0.10–0.99%. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of these PAMs can be determined from cyclic voltammograms as 4.86–5.43 and 3.31–3.34 eV, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4921–4932, 2007     

The evolution of the cluster size distribution in a coagulation system

The coagulation equation with kernelK _ij =A+B(i+j)+C _ij and arbitrary initial conditions is studied analytically and a simple expression for the solution is found. For monodisperse initial conditions, we recover the known size distribution expressed in terms of a degeneracy factorN _k, which is determined by a recursion relation. For polydisperse initial conditions, a similar solution form is found, which includes a degeneracy factorN _kl, also determined by a recursion relation. The physical meaning ofN _kl and the recursion relation is given. A method to get explicit expressions forN _k andN _kl is illustrated. Finally, the pre-gel solution is given explicitly and a general method to get the post-gel solution is proposed.     

Synthesis of aromatic poly(thioether ketone)

Aromatic poly(thioether ketone)s were prepared by the direct polycondensation of aromatic dicarboxylic acids with aryl compounds containing ether or sulfide structures using phosphorus pentoxide/methanesulfonic acid (PPMA) as a condensing agent and solvent. Polycondensation proceeded smoothly and produced aromatic poly(thioether ketone)s with inherent viscosities up to 0.73 dL/g. The synthesis of substituted aryl ketones by the reaction of substituted benzoic acids with aryl compounds in PMMA was studied in detail to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(thioether ketone)s showed a 10% weight loss in air and nitrogen at around 450 and 460°C, respectively. © 1992 John Wiley & Sons, Inc.     

Synthese und Struktur von γ-Halogenpropyl-octa(silasesquioxanen)

Synthesis and Structures of γ-Halopropyl-octa(silasesquioxanes) As a more rapid and versatile synthetic approach, we have studied the FeCl₃-catalyzed hydrolytic polycondensation of suited trichlorosilanes in a biphasic system which yields e.g. the new octa(silasesquioxane) (BrCH₂CH₂CH₂)₈Si₈O₁₂.     

Synthesis of poly(p‐phenylene sulfide) from bis(4‐bromophenyl) disulfide

Improved reaction conditions for the preparation of poly(p‐phenylene sulfide) (PPS) directly from bis(4‐bromophenyl) disulfide (BBD) have been established. Heating BBD with magnesium metal afforded only a low molecular weight polymer. PPS with a melting temperature around 280 °C was obtained from BBD in the presence of sodium carbonate or zinc metal. The best results were obtained with the addition of a catalytic amount of KI to the zinc–BBD mixture. Polymers prepared by the above methods are semicrystalline and dissolve in 1‐chloronaphthalene and have properties comparable to commercial PPS. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 900–904, 2006