Materials Literature
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The lamellar morphologies of linear polyethylene crystallized from the melt in vacuo have been surveyed. It is shown that spherulites form by the outward growth of dominant lamellae along b, with low angle branching, with the intervening spaces subsequently filled by subsidiary lamellae. There are three principal habi…
Abstract Presence of water was found to be essential to maintain the Keggin structure of 12-molybdophosphoric acid (PMo12). Hydronium ion was detected by IR at high water contents. PMo12 was almost pure Brönsted acid as seen from IR spectra of adsorbed pyridine. Dependencies of the spectra on time, temperature, and pr…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of carbon atom pyramidalization on the bonding in ethyleneWalter V. Volland, Ernest R. Davidson, and Weston Thatcher BordenCite this: J. Am. Chem. Soc. 1979, 101, 3, 533–537Publication Date (Print):January 1, 1979Publication History Published online1 May 2002Published…
Description This publication provides guidelines for choosing a particular test technique. 14 papers provide a basis for future experiments to establish parameters for determination of accurate values of toughness and crack velocity.
Small-angle neutron scattering (SANS) of semicrystalline polyethylene is computed using a Monte Carlo technique similar to that used by Yoon and Flory. Models of polymer chains with substantial amounts of chain folding (with a probability of adjacent re-entry of 0.6–0.8) are shown to give the following: (1) proper den…
ABSTRACT Water is desorbed from apples in two stages. The initial stage is characterized by a very fast release of water. The second stage corresponds to low moisture contents and a low rate of desorption. The process can be mathematically modeled in different ways depending on whether or not the true tissue structure…
Abstract The biosynthesis of fatty acids in the diatom Phaeodactylum tricornutum was studied. The diatom was incubated with sodium [1 14 C] acetate and the acids [1‐ 14 C] palmitic, [1‐ 14 C] stearic, [1‐ 14 C] linoleic and [1‐ 14 C] α‐linolenic. The distribution of radioactivity in the products was determined by gas…
The chemical diffusion coefficient was measured for undoped, single‐crystalline NiO at 900° to 1200°C and within an oxygen partial pressure of 10 −5 to 0.21 atm. Electrical conductivity was used to monitor the reequilibration kinetics after the oxygen pressure was suddenly changed over the initially equilibrated NiO c…
[Au9L8]3+(L = PPh3) reacts with L to give the new dication [Au8L8]2+; an X-ray analysis of [Au8(PPh3)8](aliz)2(aliz = alizarinsulphonate) shows that the central gold atom, while still displaying the usual short interactions with all the peripheral metal atoms, is no longer confined in an entirely metallic cage, but is…
1-(5-Amino-5-carboxypentyl)pyridinium chloride (3) and 1-(5-amino-5-carboxypentyl)-3-[1-(5-amino-5-carboxypentyl)-2-piperidyl]pyridinium chloride, anabilysine (4), have been isolated from acid hydrolysates of glutaraldehyde-treated ovalbumin and their structures confirmed by synthesis. It is concluded that the strong…
Abstract Polytetrafluoroethylene (PTFE) was extruded from a capillary rheometer at temperatures between the first‐order transition at 30°C and the melting point. Both PTFE at 50–300°C and various smectic states of certain low‐molecular benzylidene anilines obey the following relationship between the shear stress τ and…
The synthesis of symmetrically as well as unsymmetrically substituted tetraphenyl-21,23-dithiaporphyrins (S2TPP) is described. The reaction of 2,5-dilithiothiophen with substituted benzaldehydes is used for the preparation of substituted 2,5-bis(phenyihydroxymethyl)thiophens. Symmetrically substituted S2TPP molecules…
Both manganese(II) and (III) porphyrins exhibit low-intensity, short-lived luminescence in ethanol solution at 77 K. Manganese(II) porphyrins are stable towards photodecomposition when irradiated in fluid solution but undergo efficient photoreduction in the presence of a good hydrogen donor such as ascorbic acid. Mang…
Before appropriate preventative measures can be chosen to avoid any corrosion problem the latter needs to be anticipated and predictability possibly poses greater difficulties in relation to stress corrosion than many other modes of corrosion related failure. Consequently some recent work on predicting environmental r…
Surface states of nylon 6, polyethylene, and polypropylene are investigated using external photoelectric emission. These polymers seem not to have exact threshold energies. The top edges of the filled surface-states of polymers are located near 4 eV from the vacuum level. From the measurement of electron-irradiated sa…
It is suggested that the ion condensation hypothesis, previously used for polyelectrolyte solutions, also describes the ion binding in lyotropic liquid crystals formed in mixtures of amphiphiles and water. Counterion n.m.r. quadrupole splittings of these systems are shown to be appropriate for testing the ion condensa…
We discuss first the small-angle scattering of neutrons by a homopolymer melt, when each chain is tagged at certain sites by deuteration. We then extend these considerations to block copolymers AB, assuming an AB interaction which is weakly repulsive. Starting from the homogeneous melt, we lower the temperature and de…
Early theoretical predictions that amorphous and liquid polymers should be devoid of significant order down to dimensions commensurate with the diameter of the chain are supported by an extensive body of evidence from X-ray scattering at small and at wide angles, neutron scattering at small and at intermediate angles,…
Abstract A simple method has been suggested for the fractionation of polysuccinimide (PSI); the intrinsic viscosities of fractions were measured and the parameters of the Mark‐Houwink equation were determined. The possibilities of reactions of PSI with primary amines such as histamine, tyramine, tryptamine, mono‐BOC‐e…
A number of esters and other compounds containing a trans-1,4-substituted cyclohexane ring system-have been prepared, and the liquid crystal thermal stabilities of these new mesogens are discussed in relation to those of their analogues containing the 1,4-phenylene ring. The observed effects are discussed in terms of…