Diffusion-controlled stress-relaxation in polymers,I

Summary The “chemical” relaxation of stress either in Amilan (6-Nylon) or polyvinyl alcohol caused by penetration of water vapor was studied at 40% R. H. and temperatures 15, 30, and 50° C. A theory was presented of the chemical relaxation in a polymer which comprises penetrant-sensitive bonds as the crosslinkages between the molecular chains. This theory assumes the diffusion coefficient of penetrant in the polymer to he independent of concentration and any other factors. It was found that the system Amilan-water behaves in exact conformity with the theory over the ranges of elongation and temperature studied. The diffusion coefficient,D, of water in Amilan could thus be evaluated from the chemical relaxation data, using the theory presented, as functions of elongation and temperature. An ordinary sorption experiment was carried out for this system at 40% R. H. and 16.8° C and demonstrated that the diffusion of water in Amilan was Fickian with a constant diffusion coefficient. Both diffusion coefficients from the chemical relaxation data and the sorption. data were found to agree quite well when the former was extrapolated to zero-strain. The chemical relaxation behavior in the system polyvinyl alcohol-water was markedly different from that expected from the theory, suggesting primarily that the diffusion coefficient of water in this polymer was not constant. A parallel evidence for this fact was obtained from sorption measurements on this system, which demonstrated the diffusion in this system to be dependent both on concentration and time. From these results it may be concluded that the chemical relaxation technique, when combined properly with an adequate theory, can be used not only to evaluate the diffusion coefficient of penetrant in a given polymer solid but also to investigate, at least qualitatively, the type of sorption behavior characteristic of the system under given experimental conditions.

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Zusammenfassung Die chemische Spannungsrelaxation in Amilan (6-Nylon) und Polyvinylalkohol, verursacht durch Eindringen von Wasserdampf, wurde bei 40% r. F. und Temperaturen von 15, 30 und 50° C untersucht. Es wird eine Theorie der chemischen Relaxation von Polymeren vorgelegt, die als empfindliche Bindungen auf das eindringende Niedermolekulare die Vernetzungen zwischen den molekularen Ketten betrachtet. Diese Theorie setzt voraus, da? der Diffusionskoeffizient im Polymeren für die eindringende Substanz unabh?ngig von Konzentration und anderen Faktoren ist. Das System Amilan-Wasser benimmt sich vollkommen entsprechend dieser Theorie in den studierten Verstreckungs- und Temperaturbereiche. Der Diffusionskoeffizient von Wasser in Amilan konnte daher aus der chemischen Relaxation als Funktion von Dehnung und Temperatur ausgewertet werden. Ein normales Quellungsexperiment wurde für das System bei 40% r. F. und 16,8° C ausgeführt und zeigte, da? die Diffusion von Wasser in Amilan dem Fickschen Gesetz mit konstantem Diffusionskoeffizienten folgt. Beide Diffusionskoeffizienten, der aus chemischer Relaxation und der aus Quellungsdaten gewonnene, stimmten sehr gut überein, falls der erstere auf die Dehnung 0 extrapoliert wurde. Die chemische Relaxation des Systems Polyvinylalkohol-Wasser war merklich anders als nach der Theorie erwartet und lie? in erster Linie vermuten, da? der Diffusionskoeffizient von Wasser in diesem Polymeren nicht konstant ist. Eine entsprechende Andeutung wurde aus Quellungsmessungen an diesem System erhalten. Die Diffusion h?ngt von Konzentration und Zeit ab. Aus diesen Resultaten kann gefolgert werden, da? die Technik der Untersuchungen der chemischen Relaxation unter Verwendung einer geeigneten Theorie nicht nur dazu angewendet werden kann, Diffusionskoeffizienten von kleinen Molekülen in einem gegebenen festen Polymeren zu messen, sondern zumindest auch qualitativ den Typ des Quellungsverhaltens festzustellen, der das System unter den gegebenen experimentellen Bedingungen charakterisiert.

     

Total synthesis of cis-solamin

[structure: see text] A convergent total synthesis of cis-solamin and its diastereomer was accomplished using VO(acac)2-catalyzed diastereoselective epoxidation followed by cyclization of bis-homoallylic alcohol as the key step. By comparison of the optical rotation of two possible diastereomers, it is suggested that the absolute configuration of natural cis-solamin is 1a.     

Regiospecific allylation of acetals with allylsilanes catalyzed by iodotrimethylsilane. Synthesis of homoallylethers

Allylation of acetals with allylsilanes is catalyzed by iodotrimethylsilane to give the corresponding homoallyl ethers, with regiospecific transposition of the allyl group.     

Polymerization of allyl esters of unsaturated acids. V. Cyclopolymerization of methyl allyl fumarate

The kinetics of radical polymerization of methyl allyl fumarate (MAF) is discussed in terms of cyclopolymerization and compared with the polymerization results of methyl allyl maleate (MAM) as a cis isomer. In the polymerization of MAF, the rate and degree of polymerization were quite enhanced compared with MAM, and gelation occurred at low conversion. The content of the unreacted allylic double bonds of the MAF polymer was quite large; whereas those of the unreacted fumaric double bonds and the cyclic structural units showed reverse tendencies. Only a slight presence of a five-membered ring was observed in the MAF polymer. The cyclization constants K_A and K_V, the ratios of the rate constants of the unimolecular cyclization reaction to those of the bimolecular propagation reaction of the uncyclized allylic and fumaric radicals, were estimated to be 2.73 and 1.48 mole/liter, respectively. These values suggest the great difference in the cyclopolymerization behavior between two isomeric monomers. These results are discussed in detail in connection with the high reactivity of the fumaric double bond compared to the maleic double bond. In addition, the formation mode and the sequence distribution of the structural units of the polymer produced are discussed on the basis of these analytical results. Thus, for the MAF polymer obtained in the bulk polymerization, about 60% of the cyclic structure can be formed via the intramolecular attack of the uncyclized fumaric radical on the allylic double bond, as opposed to the case of MAM via the predominant intramolecular attack (ca. 90%) of the uncyclized allylic radical on the maleic double bond; these results and the low probability for the succession of cyclic structures and the rather high probability of a vinyl-to-vinyl addition are presented.     

On fluctuations in μ-space

A master equation is derived microscopically to describe the fluctuating motion of the particle density in . space. This equation accounts for the drift motion of particles and is valid for any inhomogeneous gas. The Boltzmann equation is obtained from the first moment of this equation by neglecting the second cumulant (the pair correlation function). The successive moments form coarse-grained BBGKY-like hierarchy equations, in which small spatial regions with r_ij < the force range are smeared out. These hierarchy equations are convenient for investigating the nonequilibrium long-range pair correlation function, which arises mainly from sequences of isolated binary collisions and gives rise to the much-discussed long-time tail and the logarithmic term in the density expansion of transport coefficients. It is shown to have a spatial long tail, like the Coulombic potential, in a steady laminar flow. The stochastic nature of the nonlinear Boltzmann-Langevin equation is also investigated; the random source term is found to be expressed as a linear superposition of Poisson random variables and to become Gaussian in special cases.     

Cloud point extraction equilibrium of lanthanum(III), europium(III) and lutetium(III) using di(2-ethylhexyl)phosphoric acid and Triton X-100

The cloud point extraction behaviors of lanthanoids(III) (Ln(III) = La(III), Eu(III) and Lu(III)) with and without di(2-ethylhexyl)phosphoric acid (HDEHP) using Triton X-100 were investigated. It was suggested that the extraction of Ln(III) into the surfactant-rich phase without added chelating agent was caused by the impurities contained in Triton X-100. The extraction percentage more than 91% for all Ln(III) metals was obtained using 3.0 × 10⁻⁵ mol dm⁻³ HDEHP and 2.0% (v/v) Triton X-100. From the equilibrium analysis, it was clarified that Ln(III) was extracted as Ln(DEHP)₃ into the surfactant-rich phase. The extraction constant of Ln(III) with HDEHP and 2.0% (v/v) Triton X-100 were also obtained.     

Self-crosslinkable polymers. I. Copolymerization of glycidyl methacrylate with 2-vinylpyridine and 2-vinyl-5-ethylpyridine

A soluble and self-crosslinkable linear copolymer with pendant epoxy and pyridyl groups was obtained from glycidyl methacrylate (M₁) and 2-vinylpyridine (M₂) or 2-vinyl-5-ethylpyridine (M₂) by the action of azobisisobutyronitrile. The monomer reactivity ratios were determined in tetrahydrofuran at 60°C: r₁ = 0.510, r₂ = 0.620 with 2-vinylpyridine and r₁ = 0.57, r₂ = 0.62 with 2-vinyl-5-ethylpyridine. These were consistent with the calculated values with the reported Q and e values for these monomers. The intrinsic viscosities of the copolymers with 2-vinylpyridine and with 2-vinyl-5-ethylpyridine were found to be 0.17–0.19 and 0.26–0.38, respectively, in tetrahydrofuran at 30°C; they were independent of the copolymer composition. The copolymers were amorphous, had no clear melting points, and became insoluble crosslinked polymers under heating without further addition of any curing agents.     

Isomerization polymerization of β-propiolactones carrying side-chain ester groups

Based on our recent discovery of the isomerization polymerization of β-(2-acetoxyethyl)-β-propiolactone into poly-δ-ester,^1,2 we examined the generality of this phenomenon by using two related monomers. The catalysts were (EtAlO)_n and Et(ZnO)₂ZnEt. The side-chains in the monomers selected were the (CH₃)₂CHCOO? CH₂CH₂? (2) and (CH₃)CICHCOO? CH₂CH₂? (3) groups in which steric effects are almost identical but electronic effects are in opposition. The monomers yielded isomerized poly-δ-ester units, depending on the terminal substituent groups in the side-chain. These observations can be interpreted with the bicyclic intermediate proposed in the earlier work. Monomer (2) was reactive and produced a poly-δ-ester structure most readily, probably because of the higher electron density at the side-chain ester group which coordinated with the catalyst. In contrast, monomer (3) was less reactive, and the probability of isomerization was the lowest, i.e., the electron deficient side-chain ester group apparently interfered with the formation of the intermediate, especially in the Zn-catalysis. Equibinary random copolymers were prepared from (2) and (3) according to the catalyst and polymerization conditions chosen.     

Diacetoxylation of conjugated dienes with thallium(III) acetate in acetic acid

The reaction of conjugated dienes such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2,5-dimethyl-2,4-hexadiene, 1,3-cyclopentadiene, and 1,3-cyclohexadiene, with thallium(III)acetate in acetic acid at 10–65° for 0.5–15 hr affords an isomeric mixture of the corresponding diacetoxyalkenes (1,2- and 1,4-addition products) in 10–92% yields. The 1,2-addition products are predominantly formed in all cases examined except the case of 1,3-cyclopentadiene. The reaction is assumed to proceed through acetoxythallation and dethallation steps, the latter step being accompanied and/or followed by an attack of acetoxyl group. An initial attack of thallium moiety is proposed to occur mainly at C-1 and C-2 carbons in the cases of linear terminal dienes and cyclic dienes, respectively.