Model reaction for thermally latent curing through addition of hemiacetal ester and epoxide by schiff‐base–zinc halide complexes

Schiff‐base–zinc halide complexes (ZnX₂/ 1 ) thermal‐latently catalyze the reaction of glycidyl phenyl ether (2) and 1‐propoxyethyl 2‐ethylhexanoate (3) that proceeds at moderately elevated temperatures. The catalysis by the ZnX₂/ 1 complexes proceeds via the thermal dissociation of 3 to produce the corresponding carboxylic acid that nucleophilically attacks 2 predominantly over the thermally dissociated vinyl ether. ZnX₂/ 1 complexes catalyze both the dissociation of 3 to produce the carboxylic acid intermediate and its addition to 2 . Although conventional latent catalysts for this reaction exhibit Lewis acidities under ambient conditions that are responsible to the gradual degradation of hemiacetal esters and the polymerization of epoxides, a mixture of 2 , 3 , and ZnX₂/ 1 can be stored for 3 months at ambient conditions. The stored mixture is as active as the freshly prepared mixture, keeping the excellent activity and latency of ZnX₂/ 1 . As well as the model reaction, the thermally latent polyaddition of bisphenol A diglycidyl ether (9) and di‐1‐propoxyethyl adipate (10) is also promoted with ZnCl₂/ 1 at a moderate elevated temperature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3370–3379, 2007     

238U Mössbauer study on the magnetic properties of uranium-based heavy fermion superconductors

We have performed ²³⁸U Mössbauer spectroscopy of uranium-based heavy fermion superconductors, UPd₂Al₃ and URu₂Si₂, in order to investigate their physical properties, mainly their magnetic properties. The slow relaxation of magnetic hyperfine interaction in a paramagnetic state and the static hyperfine field has been observed in an antiferromagnetic ordered state for each compound. The line-widths have maximum at their characteristic temperatures where their magnetic susceptibilities have maximum values.     

Relaxation kinetics of the long-range order parameter in a non-uniform system studied by the phase field method using the free energy obtained by the cluster variation method

The order-order relaxation process of the long-range order parameter in the non-uniform L1 0 ordered phase is investigated by the hybridized calculation using the phase field method (PFM) and the cluster variation method (CVM). The resultant kinetics are composed of three processes sufficiently differing in the relaxation rates. The first and second processes correspond to antisite ordering-disordering relaxation within the ordered domain and relaxation due to a wetting-antiwetting of the antiphase boundary respectively. The third process is due to a coarsening of the ordered domain and its relaxation rate is fairly slow compared with the relaxation rates of the first and second processes; this is consistent with experimental observation. It is noted that the present result of relaxation kinetics involving the three processes is obtained only by the hybridized calculation using the PFM and CVM.     

Microparticle separation with an acoustic-gravity field controlled by phase-shift operation.

The elution of particles from a coupled acoustic-gravity channel has been controlled by a phase-shift operation. Two ultrasound transducers pasted onto the top and bottom walls of a separation channel were driven at the same frequency, but with different phases. Changing the phases of the ultrasounds has allowed the formation of a node near the channel wall, and particles are retained in the channel. Two types of particles are separated under an appropriate condition.     

Thermal decomposition of 1-butyne in shock waves

1-Butyne diluted with Ar was heated behind reflected shock waves over the temperature range of 1100–1600 K and the total density range of 1.36 × 10^?5?1.75 × 10^?5 mol/cm³. Reaction products were analyzed by gas-chromatography. The progress of the reaction was followed by IR laser kinetic absorption spectroscopy. The products were CH₄, C₂H₂, C₂H₄, C₂H₆, allene, propyne, C₄H₂, vinylacetyiene, 1,2- butadiene, 1,3-butadiene, and benzene. The present data were successfully modeled with a 80 reaction mechanism. 1-Butyne was found to isomerize to 1,2-butadiene. The initial decomposition was dominated by 1-butyne → C₃H₃ + CH₃ under these conditions. Rate constant expressions were derived for the decomposition to be k₇ = 3.0 × 10¹⁵ exp(?75800 cal/RT) s^?1 and for the isomerization to be k₄ = 2.5 × 10¹³ exp(?65000 cal/RT) s^?1. The activation energy 75.8 kcal/mol was cited from literature value and the activation energy 65 kcal/mol was assumed. These rate constant expressions are applicable under the present experimental conditions, 1100–1600 K and 1.23–2.30 atm. © 1995 John Wiley & Sons, Inc.     

Viscoelastic properties of heterogeneous network polymers from poly(D-glutamic acid) and poly(oxyethylene glycol)

A series of five heterogeneous network polymers was prepared from poly(D -glutamic acid) (PDG) and poly(oxyethylene glycol) (PEG), and their dynamic mechanical properties were studied. The content of PDG was fixed at 60% by weight, and the molecular weight of PEG was changed to obtain networks with various crosslink densities. An increase in the PEG molecular weight from 330 to 880 caused considerable broadening of tan δ and E″ curves, and peak temperatures for tan δ and E″ decreased slightly. Curves of tan δ and E″ for PDG–PEG 4000 (indicating a PEG component of molecular weight 4,000) were much broader and the existence of two peaks was recognized. These findings and x-ray photographs suggest that PDG–PEG 330, 570, and 880 give films of fairly uniform phase, but that PDG–PEG 1830 and 4000 give films with two-phase structure. The factors influencing the dynamic mechanical properties in decreasing order of effectiveness are found to be the proportions by weight of PDG and PEG, the compatibility of PDG with PEG, the crosslink density, and the concentration of free carboxyl groups. The infrared spectra of these polymers indicate that at least part of the PDG component retains the α-helix conformation.