Electrochemical and chemical polymerization of acrylamide

The electrochemical and chemical polymerization of acrylamide (AA) has been studied. The electrolysis of the monomer in N,N-dimethylformamide (DMF) containing (C₄H₉)₄NClO₄ as the supporting electrolyte leads to polymer formation in both anode and cathode compartments. The cathodic polymer dissolves in the reaction mixture and the anodic polymer precipitates during the course of polymerization. A plausible mechanism for the anodic and cathodic initiation reaction has been given. The chemical polymerization of acrylamide that has been initiated by HClO₄ is analogous to its anodic polymerization. The polymer yield increases with an increase in concentration of the monomer and HClO₄. Raising the reaction temperature also enhances the polymerization rate. The overall apparent activation energy of the polymerization was determined to be ca. 19 kcal/mole. The copolymerization of acrylamide was carried out with methyl methacrylate (MMA) in a solution of HClO₄ in DMF. The reactivity ratios are r₁ (AA) = 0.25 and r₂ = 2.50. The polymerization with HClO₄ appears to be by a free radical mechanism. When the polymerization of acrylamide is carried out with HClO₄ in H₂O, a crosslinked water-insoluble gel formation takes place.     

Die kathodische Reduktion von Ozon in alkalischen Elektrolyten

The cathodic reduction of ozone according to the overall reaction O₃+H₂O+2e→O₂+2OH^? was studied on bright platinum electrodes in KOH electrolytes. The rest potentials deviate from the theoretical values by ?300 to ?350 mV. They are determined by a mixed potential mechanism involving anodic evolution of O₂ and cathodic reduction of O₃ as half reactions. Steady-state polarization measurements were carried out. Extrapolation of Tafel-lines to zero over-voltage and the determination of the charge transfer resistance give current densities at the rest potential, which are analogous to exchange current densities. A single electron transfer reaction is found to be the rate controlling step, which is occurring twice for the reduction of one molecule of ozone. A cathodic reaction order of approximately zero is evaluated with respect to OH^?-ion concentration. The reaction mechanism is proposed according to $$\begin{gathered} O_3 + e \to O_3 - / \cdot 2 \hfill \\ 2O_3 - + H_2 O \to 2 OH - + O_2 + O_3 \hfill \\ \end{gathered} $$ which is consistent with experimental data.     

Stereospecific polymerization of methacrylonitrile. III. Some new catalysts for isotactic polymethacrylonitrile

Some classes of organometallic catalysts what induce stereospecific polymerization of methacrylonitrile have been found. They include organolithium aluminum compounds of the type LiAlR₄, Li[R₃AlOAlR₂], and Li[R₃AlN(R)AlR₂], organosodium aluminum compounds of the type NaAlR₄, organolithium zinc compounds of the type LiZnR₃ and Li₂ZnR₄, organomagnesium aluminum compounds of the type RMg[AlR₄] and Mg[AlR₄]₂, and organomagnesium compounds containing an Mg? N bond, such as and their related compounds. One of the features of the polymerization with these catalysts was that the crystalline polymers were formed at moderately high temperatures. Total conversion, solubility index, and molecular weight of the polymer increased with increasing polymerization temperature, as observed in the case of polymerization with diethylmagnesium catalyst. Catalysts with an Mg? N bond were found to be highly effective for the stereospecific polymerization. The acetone-insoluble fractions of the polymers gave x-ray diagrams identical to the crystalline polymer produced with diethylmagnesium. This indicates that the acetone-insoluble crystalline polymers produced with these catalysts have an isotactic structure. The viscosity–molecular weight relationship for crystalline polymer was conveniently determined in Cl₂CHCOOH at 30°C.; [η] = 2.27 × 10^?4 M^0.754.     

Reduction of Tetrachloroaurate(III) at Boron-Doped Diamond Electrodes: Gold Deposition Versus Gold Colloid Formation

Tetrachloroaurate(III) dissolved in dilute aqueous aqua regia is electrochemically reduced at boron-doped diamond electrodes to form gold metal. The reduction process is studied by voltammetric, SEM, and XPS techniques. Both the deposition of gold and the anodic stripping process are detected. The ratio of cathodic to anodic charge or stripping efficiency, Q_anodic/Q_cathodic, is shown to depend on the concentration of AuCl and on the pretreatment of the boron-doped diamond electrode surface. Cathodic pretreatment of the boron-doped diamond electrode considerably increases the rate for both deposition and stripping. In the presence of power ultrasound emitted from a glass horn system (24 kHz, 8 Wcm⁻²) the current associated with the reduction of AuCl is considerably enhanced and two components in the mass transport controlled limiting current are identified as (i) the deposition of gold onto the boron-doped diamond and (ii) the formation of colloidal gold.     

Glow discharge polymerization of tetramethylgermanium

A glow discharge polymerization technique was applied in the preparation of germanium-containing polymers. The colorless and transparent polymer films formed from tetramethylgermanium (TMG) were investigated by elemental analysis, infrared (IR) spectroscopy, and ESCA. The reaction of TMG was accompanied by the rupture of bonds between Ge and CH₃ groups which led to mixtures of polymers that consisted of CH₃, CH₂, Ge? CH₃, Ge? O? C, and Ge? O? Ge groups and germanium metal. Most Ge species present at the outermost layers of the films were oxidized subsequently by air, whereas the Ge species at the inner layers still existed as Ge metal. This film-forming process can be explained by the concept of atomic polymerization proposed by Yasuda.

1 See H. Yasuda, J. Polym. Sci. Macromol. Rev., 16 , 199 (1981).

     

Phosphorus-containing polyurethans

Phosphorus-containing polyurethans of the formula were prepared by interfacial polymerization of 1,4-butanebischloroformate and p-xylylene-α, α-bischloroformate with bis(m-aminophenyl)alkylphosphine oxides. The polymers had number average molecular weights up to 8600. A test of the stability to alkali of one of the polymers (R?CH₃, X?1,4-C₆H₄) showed it to be as resistant as nonphosphorus analogs, and a film of this polymer exhibited self-extinguishing properties. Thermal degradation of the phosphorus polymers, which began at approximately 230°C, occurred by an initial first-order process, releasing chiefly carbon dioxide. The energies of activation for the maximum rates of weight loss were 31–37 kcal/mole.     

Kinetics of the reaction between methane and iodine from 830 to 1150 K in the presence and absence of oxygen

The formation of methyl iodide was determined by radiochemical methods and by massspectroscopic analyses in mixtures of Ar–CH₄–I₂ and Ar? CH₄? I₂? O₂, heated by a reflected shock wave to temperatures of 830–1150 K. The rate of formation of CH₃I was consistent with the chain mechanism where the indicated rate constant for reaction between I and CH₄ is given by k₂(cm³/mol · s) = 10^14.17 exp(?32.9 ± 0.8 kcal/mol/RT). No effect on the reaction rate by the presence of O₂ was detected. However, in one experiment at 1097 K with 3.86 mol % O₂ the formation of CH₂O was indicated by the mass-spectroscopic analysis, presumably from the reaction of O₂ with CH₃.     

Preparation of silicon-containing polymers. I. Polyimides from dianhydrides and organosilicon diisocyanates

New silicon-containing polyimides have been prepared by the reaction of pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) with organosilicon diisocyanates having the following general structure: where R₁ = R₂ = ? CH₃ and ? C₆H₅. Thermal properties of these polyimides were studied were by TG, DTA, and DTG.     

Die Umsetzung von PF5 · CH3CN mit Hydrogensulfid

Reaction of PF₅ · CH₃CN with Hydrogensulfide The reaction of PF₅ · CH₃CN with SH^? proceeds with cleavage of the P? F bonds and/or by transformations of the coordinated CH₃CN. The following species have been assigned in NMR spectra: of which the first three have been isolated as salts. The course of the reaction is discussed and a comparison is made to the reaction of AsF₅ · CH₃CN with SH^?.     

Polymerization of propylene carbonate

Polymerization of propylene carbonate was carried out at 120–180°C mainly with the use of diethylzinc catalyst. The polymer was a pale-yellow, viscous material of relatively low molecular weight (1000–4000). From the spectroscopic analysis of the polymer and its hydrolyzed product, the polymer was determined to have the structure where x ? 0.50, y ? 0.25, and z ? 0.25. This strongly suggested that the polymerization of propylene carbonate proceeded via 2,7-dimethyl-1,4,6,9-tetraoxaspiro[4,4]nonane (DTN) as an intermediate compound. Hence, DTN was synthesized and polymerized with the use of diethylzinc catalyst. The structure of the polymer thus prepared coincided exactly with that of the polymer from propylene carbonate. From these, a plausible mechanism of the polymerization was developed.     

New Quenching Procedure for Preservation of Initial Polymer/Catalyst Particle Morphology in Ziegler–Natta Olefin Polymerization

Preservation of initial polymer/catalyst particle morphology under air, was examined using stopped‐flow Ziegler–Natta polymerization with various quenching conditions and post‐chemical treatments. The exposure of the initial particles to air caused the fast formation of cracks on the surface, finally leading to significant reformation of the particle shape, when polymerizing particles were washed with heptane at ?65 °C under N₂ or under CO₂. On the other hand, when the particles were washed with heptane containing an appropriate amount of tetrahydrofuran under CO₂, the particle morphology under air was almost completely maintained even after 1 h exposure. The present results are useful for various ex situ characterizations of unstable initial polymer/catalyst particles.

     

End-Functionalized polymers by living cationic polymerization. IV. Poly(vinyl ethers) with acidic or basic terminal groups by functional initiator method

Carboxylic acid or primary amine-terminated poly(isobutyl vinyl ethers) were synthesized by living cationic polymerizations with functionalized initiators (CH₃CHIO? CH₂CH₂ ? X; X: that are the adducts of the corresponding vinyl ethers (CH₂ ? CH ? OCH₂CH₂? X) with hydrogen iodide. In the presence of iodine, these initiators induced living cationic polymerization of isobutyl vinyl ether to give polymers with the α-end group of X originating from the initiators. The polymer molecular weights were regulated by the monomer to initiator feed ratio and the molecular weight distributions were very narrow (M _w/M _n ≤ 1.15). Subsequent deprotection of the terminal group X led to polymers with a terminal carboxylic acid or primary amine. ¹H- and ¹³C-NMR analyses showed that the end functionalities of these polymers were all close to unity.     

RAFT Synthesis in Water of Cationic Polyelectrolytes with Tunable UCST

Cationic polyelectrolytes showing an upper critical solution temperature (UCST) are synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization in water at a temperature well above the UCST. The polymerization is well controlled by the RAFT process, with excellent pseudo‐first‐order kinetics. The cloud point is highly dependent on the polyelectrolyte concentration, molecular weight, and presence of added electrolyte. Alkylation of a neutral polymer is also conducted to obtain polyelectrolytes with different hydrophobic groups, which are shown to increase the cloud point.

     

Design of monomers for nonshrinking polymerizations,and synthesis of some N,S-analogs of spiroorthocarbonates

The design of spiroorthocarbonate monomers (SOCs) and related structures is discussed with the aim of maximizing monomer polymerizability in the absence of undesirable byproducts. The successful syntheses of N,S-analogs of aryl- and alkaryl-SOCs are reported; these are monomers of structure where P and Q are ? O? and ? OC(CH₃)₂?, mp 156–158°C; and P and Q are ? OCH₂? and ? OCH₂? , mp 148–150°C. As is indicated by infrared spectra, the polymerization of both monomers is initiated by boron trifluoride etherate. © 1993 John Wiley & Sons, Inc.     

Electrogenerated Chemiluminescence of Lucigenin in Ethanol Solution at a Polycrystalline Gold Electrode

The electrogenerated chemiluminescence (ECL) behavior of lucigenin in ethanol solution at a polycrystalline gold electrode was studied under conventional cyclic voltammetric conditions. Compared with the ECL of lucigenin in aqueous solution, one cathodic ECL peak (ECL‐1 at ?0.98 V versus SCE) with a shoulder (S₁ at ?0.42 V) and three new anodic ECL peaks (ECL‐2 at ?0.53 V, ECL‐3 at 0.20 V, and ECL‐4 at 0.51 V) were observed, respectively, on the curve of ECL intensity versus potential. The effects of initial potential scan direction, the presence of O₂ or N₂, potential scan ranges, supporting electrolyte and the concentration of lucigenin on these ECL peaks were examined. The electrochemistry of lucigenin in ethanol solution was also studied. The emitter of all ECL peaks was identified as N‐methylacridone (NMA) by analyzing the ECL spectra. The mechanism for these ECL peaks is proposed to be due to the reactions of lucigenin and its redox products such as Luc and DBA with dissolved oxygen or O₂ electrogenerated by the dissolved oxygen at different potentials. The formation of new anodic ECL peaks in ethanol solution is due to longer lifetime of superoxide ions and easier electro‐oxidation of DBA in nonaqueous solution, revealing that the solvent plays an important role in the lucigenin ECL reactions.     

Influence of catalyst depletion or deactivation on polymerization kinetics. III. Solution polymerization of acrylonitrile in N,N-dimethylformamide at −30°C.

The experimental results on homogeneous polymerization of acrylonitrile initiated with the sodium triethylthioisopropoxyaluminate, NaAlEt₃S(i-Pr), catalyst in DMF at ?30°C. are compared with the prediction of equations based on a postulated mechanism. The agreement between the calculated and observed number-average molecular weight combined with the kinetic data and the relationship between the conversion and the initial catalyst concentration provides a rigorous test concerning the validity of the equations and the mechanism of the polymerization. A plausible mechanism is postulated as follows: The initiation must be relatively fast in accordance with the rate equations and the growing polymer undergoes propagation, transfer (to monomer), and deactivation simultaneously. The infrared spectrum of the low molecular weight polymer prepared at a high catalyst concentration showed strong absorption at 2337, 2205, and 1620 cm.^?1 but no absorption at 900 cm.^?1, indicating that there are two nitriles in the polymer, one of which is conjugated. The possibility of having ? CH?CH₂ groups in the polymer is ruled out by the absence of the band at 900 cm.^?1. In view of these facts, it is concluded that the polymer has a ? CH?CHCN endgroup resulting from the transfer reaction.     

Effect of anodic current on carbon dioxide reforming of methane on Pt electrode in a cell with solid oxide electrolyte

The carbon dioxide reforming of methane in a cell with a solid oxygen-conducting electrolyte:

Novel conjugated polymer containing aromatic ring and selenium in backbone: Addition polymerization of 1,4-benzenediselenol to 1,4-diethynylbenzene

A novel addition polymerization of 1,4-benzenediselenol (BDSe) to 1,4-diethynylbenzene (DEB) was carried out by UV-irradiation in toluene at 60°C under nitrogen atmosphere. The polymerization proceeded at such a fast rate as to give 60–70% yield for 6 min. A paleyellowish polymer (M?_n = 20000–30000) precipitated with the progress of the polymerization. In the presence of BPO, the polymerization also proceeded rapidly to give the polymer (M?_n = 18000) in 50% yield for 4 min. The polymer was insoluble in conventional organic solvents. In the IR spectrum of the polymer, the characteristic absorption bands of cis- and trans-vinylene groups appeared at 1340 and 940 cm^?1, respectively. The microstructures of polymers were evaluated as the cis content was 90% and the trans one was 10%, based on the model adducts of benzeneselenol and ethynylbenzene. The cis ← trans isomerization occurred with UV-irradiation: the cis vinylene group of the polymer decreased from 90 to 40% for 18 h. The electrical conductivity of the polymer was in the order of 10^?13 S/cm without dopant, but increased up to 10^?5 S/cm on I₂ doping. DSC and TG thermograms of the polymer indicated its decomposition point as 465°C under nitrogen atmosphere.     

Gas‐phase intramolecular anion rearrangements of some trimethylsilyl‐containing systems revisited. A theoretical approach

Ab initio calculations at the CCSD(T)/6‐311++G(2d,p)//B3LYP/6‐311++G(d,p) level of theory have been carried out for three prototypical rearrangement processes of organosilicon anion systems. The first two are reactions of enolate ions which involve oxygen–silicon bond formation via three‐ and four‐membered states, respectively. The overall reactions are: The ΔG (reaction) values for the two processes are +175 and +51 kJ mol^?1, with maximum barriers (to the highest transition state) of +55 and +159 kJ mol^?1, respectively. The third studied process is the following: (CH₃O)C(?CH₂)Si(CH₃)₂CH → (CH₃)₂(C₂H₅)Si^? + CH₂CO, a process involving an S_Ni reaction between ‐CH and CH₃O‐ followed by silicon–carbon bond cleavage. The reaction is favourable [ΔG(reaction) = ?39 kJ mol^?1] with the barrier for the S_Ni process being 175 kJ mol^?1. The previous experimental and the current theoretical data are complementary and in agreement. Copyright © 2009 John Wiley & Sons, Ltd.     

Metal Complexes of 4,7-Dithiadecane-1,10-dicarboxylic Acid and Allied Compounds

Silver and copper(I) complexes can be obtained from CO₂H? (CH₂)_n? S? CH₂? CH₂? S? (CH₂)_n? CO₂H when n = 1, 2, and 3 (I, II and III resp.); the compound with n = 4 (IV) fails to give these complexes. does give a silver and a copper(I) complex, while the isomeric compound again fails to give these complexes. From IV, V, and VI we prepared the corresponding disulfones.