Showing papers by "Nagoya Institute of Technology published in 1976"

Crystallization of Ca(PO3)2 Glass Below the Glass Transition Temperature

Abstract: Block specimens of Ca(PO3)2 glass crystallize easily at temperatures considerably lower than the glass transition temperature, Tg; thin blown films of the glass do not exhibit this behavior. The crystals, which are β-Ca(PO3)2 with a trace of the γ form, are identical to those formed above Tg; they exhibit “hemispherulitic” growth from the glass surface. The activation energy for crystal growth below Tg is 30 kcal/mol, which indicates that the growth mechanism differs from that in blown film samples above Tg (activation energy = 110 kcal/mol). A model for crystallization below Tgis proposed; the phenomenon is explained in terms of induced tension in the molecular chains at the glass- crystal interface.

Cationic Polymerization of Phenylbutadienes. I. Cationic Polymerization of trans-1-Phenyl-1,3-butadieiie

Abstract: trans-1-Phenyl-1,3-butadiene (1-PB) was polymerized easily by Friedel—Crafts catalysts. The polymers obtained were soluble white powders. The polymer structure was determined spectroscopically; the results suggested that 1-PB was polymerized predominantly in the fashion of a 3, 4-type cationic polymerization and that about a half of the 3, 4-double-bonds were cyclized intramolecularly during the polymerization. In the cases of SnCl4, BF3OEt2, and Ph3CSnCl5 the kinetic study was also performed. It was found in all cases that the initial rate of polymerization was proportional to the initial concentrations of both monomer and catalyst. From the molecular weight of the polymers obtained the monomer chain-transfer was shown to be mainly a terminating reaction. These kinetic results described the total scheme of cationic polymerization of this diene monomer, which was characterized by a rapid initiation. In the course of cationic polymerization of 1-PB, a colored species developed; it was followed by visible spectrum measurements. The absorption peak at 440 nm was assigned to a propagating species. The other absorption bands at 400, 493, and 570 nm were assigned to cations formed on the polymer by chain transfer.

Determination of coisotacticities of some alternating styrene–acrylic copolymers by NMR spectra

Abstract: Coisotacticities σ for some alternating copolymers were determined through the analyses of their CH3O, CH3 and CH2 proton NMR spectra; styrene–methyl methacrylate (σ = 0.56), styrene-methyl acrylate (σ = 0.53), styrene–methyl α-chloroacrylate (σ = 0.69), styrene–methacrylonitrile (σ = 0.19), styrene–methacrylamide (σ = 0.16), α-methylstyrene–methyl methacrylate (σ = 0.21), and α-methylstyrene–methyl acrylate (σ = 0.53) were studied. It was found that a terminal model or Bernoullian trial prevails in these complexed copolymerizations with diethylaluminum chloride. The influence of monomer structure on σ values is discussed.

Cationic polymerization of phenylbutadienes. III. Cationic polymerization of 2-phenyl-1,3-butadiene.

Abstract: 2-Phenylbutadiene was polymerized by SnCl4, BF3OEt2, and Ph3CSnCl5 in ethylene dichloride. The kinetic study showed a rapid initiation in the cases of SnCl4 and BF3OEt2, but a rather slow initiation in the case of Ph3CSnCl5. The initial rate of polymerization in the cases of SnCl4 and BF3OEt2 or the maximum rate in the case of Ph3CSnCl5 was expressed as follows Rp0(Rp max)=k[M]0[C]0=kp[M][Mn⊕] The molecular weight of the polymers obtained in these cationic polymerizations was independent of concentrations of both monomer and catalyst; hence, the monomer chain transfer was proposed as a terminating reaction. By IR, UV, and NMR spectroscopies, it was shown that the microstructure of the polymers obtained in these cationic polymerizations was a 1,4-structure and about a half of the double bonds in the polymers was consumed by a novel cyclization whose scheme was proposed. The UV spectrum of the propagating species of 2-phenylbutadiene in the cationic polymerization was also found to be the same as in the case of 1-phenylbutadiene.

Stochastic automaton models for the temporal pattern discrimination of nerve impulse sequences

Abstract: The application of stochastic automata to the input-output relations of single neurons is considered. For this, some stochastic properties of temporal pattern discrimination in single synaptic cells are used to suggest stochastic automaton models. The models have only three possible states, the active, the absolute refractory and the relative refractory states, which are sufficient for temporal pattern sensitivity. From such an application, it was found that the temporal pattern discriminating structures in the models are similar to those used for experimental data and computer simulation (real-time neuron models). Extensions related to temporal pattern learning are discussed.

Alternating copolymerization of styrene and methyl α-chloroacrylate with diethylaluminum chloride

Abstract: The alternating copolymerization of styrene and methyl α-chloroacrylate (MCA) with diethylaluminum chloride (Et2AlCl) in benzene at 0°C has been investigated. The copolymer has an equimolar composition irrespective of the feed monomer composition, the copolymer yield and the amount of Et2AlCl used. The copolymerization proceeds first very rapidly and then rather slowly after attaining a certain yield which varies proportionally to the amount of Et2AlCl used. A maximum copolymer yield is observed at about 60% MCA feed composition. The 1H-NMR analyses of dyad, triad, and pentad of the alternating deuterated α-d-St-MCA copolymer indicate that the configuration of this copolymer can be explained by a single parameter, coisotacticity σ(σ = 0.69). A favorable mechanism of the alternating propagation as well as of the stereoregularity control is discussed.

Cationic Polymerization of Phenylbutadienes. II. Initiation Reaction in Cationic Polymerization of Phenylbutadienes Catalyzed by Triphenylmethylstannic Pentachloride

Abstract: Initiation in cationic polymerization of phenyl-substituted 1,3-butadienes with triphenylmethylstannic pentachloride as catalyst was studied. The rates of consumption of Ph3CSnCl5 with 1-phenyl-substituted butadienes are represented by the following equation−d[Ph3CSnCl5]/dt=ki′[Ph3CSnCl5][M], where M means monomer.On the other hand, in the case of 2-phenyl-substituted butadienes the rate is represented as follows−d[Ph3CSnCl5]/dt=ki′[Ph3CSnCl5][M]+k[Ph3CSnCl5]([M]0−[M])and the formation of a π-complex between the monomer and a carbonium ion is suggested. The initiation rate constants decreased according to the following order:1-phenyl-1,3-butadiene>2-phenyl-1,3-butadiene>1,1-diphenyl-1,3-butadiene>1,2-diphenyl-1,3-butadiene>2,3-diphenyl-1,3-butadiene.1,4-Diphenyl-1,3-butadiene did not react with Ph3CSnCl5 at all. The high reactivity of phenylbutadienes toward Ph3CSnCl5 in comparison with that of vinyl monomers could be ascribed to the stabilization of allyl-type cations which were formed by an attack of a trityl cation onto the 4-position and the 1-position carbon for 1-phenylbutadienes and 2-phenylbutadiene, respectively.

Cationic Polymerization of Phenylbutadienes. IV. Cationic Copolymerization of trans-1-Phenyl-1,3-butadiene with Olefinic Monomers

Abstract: The copolymerization of 1-phenylbutadiene with olefinic monomers was performed by using isobutene, styrene, and α-methylstyrene as comonomers catalyzed by BF3OEt2 or SnCl4-trichloroacetic acid. From the monomer reactivity ratios in these copolymerizations in methylene chloride, the following order of the reactivities of the monomers is indicated: α-methylstyrene>1-phenylbutadiene>isobutene>styrene>isoprene>butadiene. This order of the reactivities will be explained by the stability of the cations formed from the monomers and by the nucleophilicity of the monomers. In the copolymerization of 1-phenylbutadiene with styrene catalyzed by BF3OEt2, the reactivity of 1-phenylbutadiene increased with increasing the polarity of the solvent in the order of nitroethane>methylene chloride>toluene. The temperature effect on the copolymerization was also recognized in such polar solvent as nitroethane. These results and the block character in the copolymerization of 1-phenylbutadiene with isobutene were interpreted on the basis of the two-step theory of propagation.

Dislocation mobility in crystals containing small amounts of impurities

Abstract: An expression is given for the dislocation velocity in crystals containing small amounts of impurities. It is of the form where U(σ) is the activation energy as a function of applied stress σ, x is the average displacement between impurities in a direction perpendicular to the dislocation, v is a frequency factor, and the other terms are defined below or have their usual meanings. The terms U(σ), x and v are represented in terms of the Friedel relation. The concentration and the temperature dependence of the velocity obtained from this formula are in agreement with available data. The stress dependence of the velocity is compared with data for the alkali halide crystals; NaCl, KBr and LiF. It is shown that the calculated values fit the measured data over many orders of magnitude, with reasonable values for the internal stress σi, the drag coefficient B, the binding energy of a dislocation with an impurity atom, and the concentration of impurity atoms.

Operation-induced degradation of GaP light-emitting diodes

Abstract: After GaP red light-emitting diodes (LED's) had been degraded by the forward-biased operation, changes of the light output, the minority carrier lifetime, the photocurrent, and the photocapacitance were measured. There was a linear decreasing relation between the light output and the carrier lifetime. A center which was related to the degradation of the light output was observed by means of photocurrent and photocapacitance measurements. This center's energy level is about 0.8 eV from either the valence or conduction band. This center was observed to increase in concentration with degradation. However, the contribution of this center to the minority carrier lifetime is not established since the capture cross sections of the center are unknown and is not known whether the center occurs on the n-side, or the p-side, or on both sides. This center does not appear to be an oxygen donor.

Cationic Polymerization of Phenylbutadienes. V. Cationic Copolymerization of Monophenyl-1,3-butadienes

Abstract: To obtain information about the transition state for the cationic polymerization of monophenylbutadienes, the ring-substituent and the temperature effects on the copolymerizability were investigated. Judging from the magnitude of the ρ+ values for the copolymerizations of styrene with ring-substituted 1- and 2-phenylbutadienes, it is suggested that the propagation of monophenylbutadiene proceeds through the transition state which involves an cyclic carbonium ion intermediate. The same interpretation could be applied for the attack of a cinnamyl-type cation onto monophenylbutadiene. The reactivity of monomers toward a styryl cation decreased according to the following order: 1-phenylbutadiene>styrene>2-phenylbutadiene. The lower reactivity of 2-phenylbutadiene in comparison with styrene may be ascribed to the enthalpy increase which overweighs the entropy increase in the transition state.