Vinyl polymerization with Fe(III)-thiourea as initiator system. Part I. General features and kinetics of Fe(ClO4)3-thiourea reaction

Initiation of polymerization of methyl methacrylate, styrene, and acrylonitrile with the redox system Fe(III)—thiourea has been examined. For the heterophase polymerization any of the ferric salts, such as FeCl₃, Fe₂(SO₄)₃, and Fe(ClO₄)₃ can be used as oxidant, but there is no polymerization in the homogeneous phase when FeCl₃ is used as oxidant. It was also observed that Fe(ClO₄)₃ retards the radical polymerization of styrene, though this salt has hardly any effect on the radical polymerization of methyl methacrylate. Further, the reaction between Fe(ClO₄)₃ and thiourea was found to be kinetically of second order. The rate is largely influenced by the nature of the solvent. It is concluded that apart from the dielectric constant of the solvents, specific effects like complex formation of Fe(III) with solvents should have a marked influence on the rate of this reaction.     

Synthesis and mechanistic studies on the aquation of selenitoaquobis(diamine)cobalt(III) complexes

Summary The kinetics of the aquation of four selenitoaquobisdiamine)cobalt(III) complexes to their respective diaquabis-(diamine)complexes (diamine=ethylenediamine en, propylenediamine pn, dimethylethylenediamine me₂en and trimethylenediamine tmd) have been carried out conductimetrically in the 25–45 °C range. All reactions exhibit simple first order kinetics, and the rates increase with increasing temperature. In aqueous solution, the complex species exist in equilibrium with their respective hydroxo species, but only the hydroxo species are involved in the aquation process. This result is also reflected in the linear Arrhenius plot. The rates are higher in a 10% alcoholic solution than in water, but then decrease with increase in the alcohol content. A Grunwald-Winstein plot of rates in methanol yields slopes of 0.18 ± 0.04, 0.27±0.03, 0.43±0.03 and 0.34±0.02 for the four amines respectively. A dissociation mechanism is proposed for the aquation of all these complexes.     

Studies on the polymerization of ethyl acrylate. III. Effect of temperature on the solvent-transfer reaction

The effect of temperature on transfer constants for different solvents in the polymerization of ethyl acrylate was observed. Activation energy differences (E_trS ? E_p) and frequency factors were computed. It is observed that high frequency factors are associated with high activation energies. Values of E_trS were calculated by an approximate method and were compared with the available data on methyl methacrylate, isobutyl methacrylate, and styrene.     

Mobility-induced instability and pattern formation in a reaction-diffusion system

Ions undergoing a reaction-diffusion process are susceptible to electric field. We show that a constant external field may induce a kind of instability on the state stabilized by diffusion in a reaction-diffusion system giving rise to formation of pattern even when the diffusion coefficients of the reactants are equal. The origin of the pattern is due to the difference in mobilities of the two species and is thus markedly different from that of deformed Turing pattern in presence of the field. While this differential flow instability had been shown earlier to result in traveling waves, we realize in the context of stationary pattern formation in a typical reaction-diffusion-advective system. Our analysis is based on a numerical simulation of a generic model on a two-dimensional domain.     

Physical and dielectric properties of poly(vinylidene fluoride)/polybenzimidazole functionalized graphene nanocomposites

Polymer‐based nanocomposites with good dielectric behavior have engrossed research devotion because of their distinctive benefits in electronic applications. An in situ synthetic process for the polybenzimidazole functionalized graphene oxide (GBI) and its nanocomposite with poly(vinylidene fluoride) (PVDF) is described. GBI shows good dispersion in the bulk PVDF matrix implying a strong interaction of polybenzimidazole with PVDF as evident from morphological and FTIR studies. A gradual increment of GBI in PVDF increases its piezoelectric β‐polymorph formation with a maximum of 73% for 10 wt % GBI in PVDF (GBF10) which also exhibits highest thermal stability. An exhaustive study of frequency dependent electrical properties of GBF10 indicates significantly higher dielectric constant (61), low dielectric loss (0.42), and low AC conductivity value of 1.17 × 10^?10 S/cm at 100 Hz which are the key properties of a suitable capacitor. GBF10 also shows hydrophobic behavior (water uptake 2.89%) and low swelling ratio (1.143), providing an opportunity to use the composite film in fuel cell application. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 189–201     

Catalyst-Controlled Dual Reactivity of Sulfonimidamides: Synthesis of Propargylamines and N-Propargyl Sulfonimidamides

Sulfonimidamides (SIAs) are acting both as surrogate amines and nucleophiles depending on the reaction conditions to access propargylamines and N-propargyl SIAs, respectively. The amine part of SIAs has been cleaved in an InCl₃-catalyzed three-component A³ coupling reaction with aldehyde and acetylene to yield propargylamine. Moreover, N-propargyl SIAs were obtained via the direct-imination of propargyl alcohols in the presence of BF₃⋅OEt₂.     

Coupled solution of the species conservation equations using unstructured finite‐volume method

A coupled solver was developed to solve the species conservation equations on an unstructured mesh with implicit spatial as well as species‐to‐species coupling. First, the computational domain was decomposed into sub‐domains comprised of geometrically contiguous cells—a process similar to additive Schwarz decomposition. This was done using the binary spatial partitioning algorithm. Following this step, for each sub‐domain, the discretized equations were developed using the finite‐volume method, and solved using an iterative solver based on Krylov sub‐space iterations, that is, the pre‐conditioned generalized minimum residual solver. Overall (outer) iterations were then performed to treat explicitness at sub‐domain interfaces and nonlinearities in the governing equations. The solver is demonstrated for both two‐dimensional and three‐dimensional geometries for laminar methane–air flame calculations with 6 species and 2 reaction steps, and for catalytic methane–air combustion with 19 species and 24 reaction steps. It was found that the best performance is manifested for sub‐domain size of 2000 cells or more, the exact number depending on the problem at hand. The overall gain in computational efficiency was found to be a factor of 2–5 over the block (coupled) Gauss–Seidel procedure. All calculations were performed on a single processor machine. The largest calculations were performed for about 355 000 cells (4.6 million unknowns) and required 900 MB of peak runtime memory and 19 h of CPU on a single processor. Copyright © 2009 John Wiley & Sons, Ltd.