Microwave spectrum of 1,2,4-trifluorobenzene

The microwave spectrum of 1,2,4-trifluorobenzene has been observed in the range 12.5–18.0 GHz and 21.5–25.3 GHz at dry-ice temperature and assigned up to angular momentum state J = 39. The ground state rotational constants and the five quartic centrifugal distortion constants thus obtained are (in MHz): à = 3084.0037 ± 0.0108, B? = 1278.3614 ± 0.0062, C? = 903.6989 ± 0.0108, d_j = ( ?4.599 ± 0.621) · 10^?4, d_jk = (5.9757 ± 1.1586) · 10^?3, d_k = (11.4923 ± 2.0886) · 10^?3, d_wj = (4.0 ± 1.0) · 10^?7, d_wk=(?5.8± 1.1) · 10^?6.The small value of Δ = 0.029 (amu Ų) shows that the molecule is planar and an r₀ - structure using a regular hexagonal benzene ring with the bond lengths C-C = 1.397 Å, C-H = 1.084 Å and C-F = 1.312 Å, reproduces the rotational constants.     

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.     

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.     

Structural hierarchy in melt-processed poly(3-hexyl thiophene)-montmorillonite clay nanocomposites: novel physical, mechanical, optical, and conductivity properties

Poly(3-hexyl thiophene) (P3HT) organically modified montmorillonite (om-MMT) polymer nanocomposites (PNCs) are prepared in the melt-cooled state. Hierarchical structures up to third order, namely, side chain mesomorph formation followed by the interchain lamellar structure of P3HT and finally its intercalation within the clay tactoids are observed. The structures are supported by transmission electron microscopy (TEM) and wide-angle X-ray scattering (WAXS) experiments. The TGA curves show two-stage degradation corresponding to those of the side chain and main chain of P3HT, and both temperatures decrease with an increase in clay concentration in the PNCs. The melting points of PNCs have increased by 2-3 degrees C higher than that of P3HT. The glass-transition temperature (Tg) and beta-transition temperature (Tbeta), measured by DMA, increase with an increase in clay concentration. The storage modulus (G) of PNCs has also increased more dramatically than that of P3HT. The UV-vis spectra of the PNCs show a blue shift in the pi-pi* absorption peak of the conjugated chain, but the photoluminescence spectra showed a red shift with an increase in the clay concentration. The quantum yield of the photoluminescence process also increases in the melt-cooled PNCs, and this is in sharp contrast to that of solvent cast PNCs where photoluminescence quenching was observed. Fibrillar network structure of the solvent cast PNCs promotes energy transfer of the charge carriers, but its absence in the melt-cooled films inhibits such energy transfer, increasing the quantum yield. The room-temperature dc conductivity of the PNCs decreased by an order compared to that of P3HT in both the doped and undoped states. The I-V characteristic curve shows semiconducting behavior, and it slowly transforms into insulator with increasing clay concentration.