Showing papers by "Research Triangle Park published in 1971"

Activity of Δ8-and Δ9-Tetrahydrocannabinol and Related Compounds in the Mouse

Abstract: The 11-hydroxy metabolites of Δ8.- and Δ9-tetrahydrocannabinol are more active than the parent compounds when administered to mice by either the intravenous or intracerebral route. Both Δ8- and Δ9-tetrahydrocannabinol are rapidly and extensively metabolized by the liver and not by the brain. The hypothesis that the 11-hydroxy metabolites may be the active form of tetrahydrocannabinol is discussed

Diffusive and hydraulic permeabilities of water in water‐swollen polymer membranes

Abstract: The diffusive permeability of water P, which relates to diffusive flux of water under a concentration gradient of water (measured by diffusion of tritiated water), and the hydraulic permeability of water K, which relates to the water flux under a hydraulic pressure gradient are defined. For the case of diffusive transport one has P = KRT/ν1, where ν1 is the molar volume of water. The relationship between P and K was investigated as a function of hydration H, i.e., the volume fraction of water in swollen polymer membranes. The following characteristic features of water permeability are revealed. (a) In the lowhydration region (H < 0.2), water permeates by diffusion even under an applied hydraulic pressure gradient and KRT/ν1 = P. (b) In the higher hydration region KRT/ν1 is greater than P, and the ratio ω = KRT/ν1P increases nearly exponentially with decrease of (1-H)/H. Water in this region moves partly by bulk flow under an applied hydraulic pressure gradient but moves only by diffusion in the absence of a pressure gradient. (c) The dependence of log P on (1-H)/H is nearly linear in regions of both high and low hydration but the slopes are different. The transition occurs in about the same H range where the discrepancy between P and KRT/ν1 becomes significant. Excellent agreement was found between the experimental data for P as a function of H and the theoretical prediction based on the free-volume concept of diffusive transport in hydrated homogeneous membranes.

Reversal of the antimicrobial activity of trimethoprim by thymidine in commercially prepared media.

Abstract: The ability of a potent dihydrofolate reductase inhibitor, trimethoprim, to inhibit the growth of Escherichia coli B in vitro is dependent on the composition of the medium in which the cells are grown. The inhibition observed in minimal broth could be partially reversed by the addition of thymidine, ribonucleosides, amino acids, and vitamins. No reversal occurred in the absence of thymidine. In a number of commercially prepared media, the inhibitory activity of trimethoprim correlated inversely with the amount of thymidine found to be present by microbiological assay. The significance of these findings for the routine testing of new, synthetic antibacterial agents is discussed.

Permselectivity of solutes in homogeneous water-swollen polymer membranes

Abstract: The concept of a homogeneous polymer membrane, in which randomly coiled macromolecules pack the solid phase uniformly leaving some unoccupied space as free volume, has been applied in the study of permeability and selectivity of solutes through water (solvent)-swollen polymer membranes. Using this treatment, it became clear that fundamental principles of permeation through polymer film, i.e., a solution and diffusion mechanism of permeation, is also applicable to these swollen systems. However, the permeability characteristics of highly swollen systems resemble that of porous media due to the presence of the solvent, and the permeability of a swollen system to a solute cannot be characterized by a single permeability coefficient. The permeabilities based on diffusive flux (molecular flow) and on bulk flow of solvent, both of which occur under certain conditions, should be differentiated. Consequently permeability and permselectivity depend on the type of processes or conditions under which permea...

Plastic deformation of polyethylene II. Change of mechanical properties during drawing

Abstract: The crystallinity, elastic modulus, and tensile strength of samples of various draw ratios together with the true stress—strain curves of high-density polyethylene were determined to establish correlations with morphological changes occurring during deformation. Changes of crystallinity at draw ratios below 5, i.e., constancy during drawing of quenched film and a decrease during drawing of annealed film, are explained by the formation of microfibrils with crystallinity independent of the thermal history of the film. The microfibrils slide past each other at higher draw ratios, generating an increasing number of interfibrillar tie molecules, which is reflected in the increasing number of interfibrillar tie molecules, which is reflected in the increase of crystallinity, elastic modulus, and tensile strength. From the true stress—strain curves, the differential work density for the deformation of the volume element was calculated as a function of the draw ratio. It contains two components which reflect two different mechanisms of deformation. The first component, decreasing with increasing draw ratio, can be associated with the destruction of the original microspherulitic structure; the second one, increasing with increasing draw ratio, can be associated with the deformation of the new fiber structure, i.e., with the sliding motion of the microfibrils formed during the first deformation step.

Small-angle X-ray diffraction studies of plastically deformed polyethylene. III. Small draw ratios

Abstract: Linear polyethylene drawn at 0, 110, and 120°C to a draw ratio between 1.1 and 6 was investigated by small- and wide-angle X-ray scattering. Besides a small increase of meridional long period at low draw ratios one observes a decrease of diagonal (at an angle φ to the meridian) and equatorial long period at high draw temperatures. This decrease is the consequence of thinning of lamellae by chain tilt in the compressional field of the uniaxial draw deformation. The early decrease of the meridional scattering intensity indicates the rapidly increasing loss of packing order as a consequences of the disappearance of lamellae oriented perpendicular to the draw direction due to rotational motion towards parallel orientation. The intensity decreases in the equatiorial scattering, however, is caused by the rapid destruction of lamellae parallel to the draw. By micronecking they are transformed into microfibrils of the new fiber structure. With increasing draw ratio the diagonal maximum shifts closer to the equator and to larger diffraction angle. It reflects the maximum of lamella population at an angle 90°−φ as a consequence of dynamic equilibrium between new arrivals from the equatorial area and continuous loss by micronecking of lamellae close to the pole. The chain tilt within the lamellae increasing with draw ratio shifts the optimum orientation for chain slip and lamellae fracture from 45° (corresponding to chains perpendicular to lamella surface) to smaller angles. At high temperature of drawing (120°C) the plastic deformation of lamellae by chain tilt and slip showing up in thinning of lamellae before the final micronecking persists up to high draw ratios (λ ∼ 4). At 0°C with practically blocked chain mobility in the crystal lattice, this contribution is limited to λ ≤ 1.5 with practically no reduction of LD or LE. The lamellae get destroyed at low λ by sliding motion of chains in the “noncrystalline” boundary layers between mosaic blocks without any substantial chain tilt in the blocks. Drawing at 110°C is much closer to the low than to the high temperature case. This temperature dependence is very similar to long period growth which is quite rapid at 120°C, just observable at 110°C, and not observable at all at temperatures below 80°C. This similarity seems to originate from the fact that in both cases one has to do with the longitudinal chain mobility in the crystal lattice. Das bei 0, 100 und 120°C zu einem Dehnungsgrad zwischen 1.1 und 6 verstreckte lineare Polyathylen wurde mit Klein- und Weitwinkelrontgenstreuung untersucht. Auser einem anfanglich geringen Anstieg der meridionalen Langperiode beobachtet man eine Abnahme der diagonalen (unter einem Winkel φ zum Meridian) und aquatorialen Langperiode bei hohen Verstreckungstemperaturen. Diese Abnahme wird durch das Dunnerwerden der Lamellen als Folge der durch den Kompressionsanteil der einachsigen Dehnungsdeformation verursachten Kettenneigung erzeugt. Die friih auftretende Intensitatsverminderung der Meridianstreuung deutet auf eine schnelle Abnahme der Packungsgute als Folge des Schwindens der senkrecht zur Dehnungsrichtung orientierten Lamellen hin, das durch eine Drehbewegung zur parallelen Orientierung verursacht ist (Abwanderung aus der Aquatorzone nach dem Pol). Die Intensitatsabnahme der aquatorialen Streuung ist dagegen eine Folge der schnellen Zerstorung der parallel zur Dehnungsrichtung orientierten Lamellen. Sie werden durch Mikroeinschnurungen in die Mikrofibrillen der neuen Faser struktur umgewandelt. Mit steigendem Dehnungsverhaltnis wanderii die Diagonalmaxima naher zum Aquator und zu gronerem Streuwinkel. Sie entspreehen dem bei einem Winkel 90° − φ zur Dehnungsrichtung gelegenen Maximum der Lamellenverteilung, die sich als Folge des dynamischen Gleichgewichtes zwischen Einwanderung von Lamellen ans der hiquatorzone und stetigem Verlust der polnahen Lamellen durch Zerstorung und Umwandlung in Mikrofibrillen einstellt. Die mit steigendem Dehnungsverhaltnis wachsende Kettenneigung in den Lamellen verschiebt die fur Kettengleitung und Lamellenzerstorung optimale Orientierung von 45°(optimaler Winkel, wenn die Ketten senkrecht zur Lamellenoberflache orientiert sind) zu einem kleineren Winkel. Bei hoher Verstreckungstemperatur (120°C) bleibt die plastische Deformation der La mellen durch Kettenneigung uud Gleitung, die sich im Dunnerwerden der Lamellen vor den Mikroeinschnurungen zeigt, bis zu sehr hohen Verstreckungsgraden (λϑ∼4) bestehen. Bei 0°C, mit praktisch aufgehobener Langsbeweglichkeit der Ketten im Kristallgitter, tritt diese Deformation nur noch bis λ ∼ 1.5 auf, ohne eine merkliche Verkleinerung von LD oder LE. In diesem Falle werden die Lamellen schon bei kleinem λ durch Gleitbewegung der Ketten in den „nichtkristallinen” Grenzfiachen zwischen den Mosaikblocken zerstort, ohne das dabei eine merkliche Kettenneigung in den Blocken stattfinden wurde. Verstrekken bei 110°C ahnelt in vieler Beziehung mehr dem Tief- als dem Hochtemperaturfall. Eine derartige Temperaturabhangigkeit ist der des Langperiodenwachs tums sehr ahnlich: sehr schnell bei 120 °C, gerade noch beobachtbar bei 110°C und unmerklich unterhalh 80°C. Diese Ahnlichkeit scheint daher zu ruhren, das es sich in beiden Fallen um die gleiche longitudinale Heweglichkeit der Molekulketten in Kristallgitter handelt.

Polymerization of styrene in an electrodeless glow discharge

Abstract: The polymerization (polymer deposition) rate of styrene in an electrodeless glow discharge from styrene vapor and a mixture of styrene vapor and gas (H2, He, A, and N2) was investigated. The rate of polymerization, R, was found to be independent of the discharge power. The rate of polymerization of the pure monomer was found to be proportional to the square of monomer pressure pM. The addition of gas increased the rate of polymerization depending upon the partial pressure of the gas, px, and R can be generally expressed by R = a[pM]2{1 + b[px]}. The value of b is dependent of the type of gas and follows the order of N2, > A > He > H2. The distribution of polymer deposition was found to be nearly independent of the partial pressure of the gas and of the discharge power with N2 and H2 as plasma gas; however, with He and A, the distribution is highly dependent on the partial pressure of the gas and on the discharge power. The study strongly suggests that polymerization occurs in the vapor phase and that the growing polymer radicals deposit on the surface of the discharge vessel, yielding highly crosslinked polymer deposition.

Folate antagonists as antibacterial and antiprotozoal agents.

Abstract: Elsewhere in this volume, Dr. Burchall has presented data which suggest that the enzyme dihydrofolate reductase has undergone manifold subtle alterations in the course of evolution. Its function has been relatively constant, however, and such changes as have occurred are nearly unmeasurable by the usual parameters of enzyme kinetics. That other changes have occurred is revealed strikingly by the diverse binding of small molecule inhibitors to dihydrofolate reductases prepared from tissues of different species. It is a reasonable interpretation that these small molecule inhibitors are bound to the enzyme partly within the active site, and partly within neighboring, supportive, hydrophobic regions. If so, it follows that regions of the enzyme outside the active site may vary considerably (presumably in amino acid sequence) without significantly altering the function of the active site. Such a pattern is now emerging as a general phenomenon from studies of hemoglobins, insulins, and other oligopeptides. The small molecule inhibitors of dihydrofolate reductase were detected first as diaminopyrimidine derivatives that had the general property of inhibiting the utilization of folic acid by Lactobacillus casei.’ Two additional characteristics soon became apparent: (1) they were in some way interfering with the reduction of folates, i.e., “the conversion of folic to folinic acid,” and ( 2 ) they were inherently selective in their action; “substituents that increased the activity against plasmodia diminished it against bacteria and vice versa.” Out of this emerged the concept that we were dealing with a group of active substances that all had the same mechanism of action in a biochemical sense but were cxhibiting selectivity because the cell receptor varied from species to species “in geometry and charge.” Such selectivity of action appeared, rather obviously, to form a basis for the development of chemotherapeutic agents. The elaboration of the concept of the mechanism of action and its documentation required developments that came gradually over an extended period and are still incomplete, since pure enzymes, sequence determinations and construction of three-dimensional models remain for the future. However, exploitation of the selective effects could proceed, and antimalarial activity seemed a particularly promising goal, since the first two compounds tested had activities equal to, and 5-times that of quinine, respectively. Through synthesis and testing, this group of substances progressed through members with higher and higher antimalarial activities, and culminated with pyrimethamine, S-p-chlorophenyl-2,4-diamino6-ethylpyrimidine, with an antimalarial activity approximately 1,000 times

Transport properties of methylene chloride in drawn polyethylene as a function of the draw ratio

Abstract: The sorption and diffusion constants of CH2Cl2 at room temperature in quenched polyethylene film drawn at 60°C to different draw ratios λ between 6 and 25 drop drastically between λ = 8 and λ = 9 and then remain nearly constant, dropping only slightly up to λ = 25. Also, the exponential dependence of diffusion constant on concentration of sorbent increases abruptly in the same draw interval and then remains constant at the higher draw ratios. The data may be explained well by a composite madel: a low-permeability fiber structure embedded in a high-permeability spherulitic matrix. As the draw ratio is increased, the initially spherulitic film is gradually transformed into the fiber structure with the transformation being completed between λ = 8 and λ = 9. During subsequent drawing to λ = 25 the mutual arrangement of microfibrils, the basic elements of the fiber structure, changes by longitudinal sliding. However, their transport properties remain nearly constant. The diffusion constant drops a little as a consequence of the increased fraction of tie molecules which reduces the number of unperturbed sorption sites.

A scheme for speech processing in automatic speaker verification

Abstract: Experiments investigating adaptive pattern recognition in automatic speaker verification are reported. A binary decision confirming or rejecting a speaker's purported identity is required. The experiments involve 7000 phrase length utterances of 118 speakers. An average misclassification rate of one percent with a "no decision" rate of ten percent is obtained. Other experiments indicate that the utterances used for training purposes should preferably be collected over a relatively long period of time.

Comparative biochemistry of dihydrofolate reductase.

Abstract: In previous studies we were able to show that reductases from bacterial and mammalian sources could be clearly distinguished from each other on the basis of their relative ability to bind a series of carefully selected small molecule analogues of dihydrofolic acid that function as competitive inhibitors of that enzyme.l This type of analysis, when presented in the form of a bar graph or curve, has been named an “inhibition profile.” It soon became clear in these early studies that, although the large differences that exist between the bacterial and mammalian enzymes could be detected by conventional characterization techniques such as pH optima and K,, values, only the inhibition profile technique possessed the high degree of sensitivity required to distinguish among reductases of these two groups. TABLE 1 illustrates the main findings of these earlier studies. In all cases, amethopterin (compound No. 1 ) is the most potent reductase inhibitor. Little difference can be noted in its potency against the enzymes from each species. However, these reductases may be distinguished from one another when the effect of a spectrum of small molecule inhibitors is studied. Thus, the reductase from Staphylococcus aureus is strongly inhibited by the 6-butylpyrido-pyrimidine (compound No. 4) whereas the enzymes from Escherichia coli and Proteus vulgaris are considerably less sensitive. On the other hand, the corresponding 5-methyl derivative is more potent against the enzymes of the gram-negative organisms. Differences among mammalian enzymes are less striking but as a group these enzymes can be clearly distinguished from bacterial enzymes. Trimethoprim (compound No. 2 ) , the most potent inhibitor of bacterial reductases, is relatively inactive on the mammalian enzymes, whereas the triazine (compound No. 3 ) is a potent inhibitor of the human and rat liver enzymes. Enzyme-inhibition data correlate well with the potencies of the compounds as inhibitors of microbial growth.’ The diameter of the zone of inhibition that each compound produced on a disc-agar plate was plotted against its 50% inhibitory concentration, determined against the E. coli dihydrofolate reductase, and a straight line function was obtained. Similar results were seen in studies with S. aureus and P. vulgaris. Thus, enzyme binding, rather than transport, nonspecific binding, or degradative reactions, appears to be the major factor in determining the activity of these inhibitors against whole cells. These studies raise a number of questions regarding the extent of variation among reductases in nature. Are the profiles shown here for the three bacterial enzymes representative of reductases from all bacterial species? Are the patterns seen with the mammalian enzymes representative of all nonbacterial enzymes, or is there a gradual change in reductase structure over the taxonomic range between bacteria and mammals? In order to answer these questions,

Plastic deformation of polypropylene. V. Annealing of drawn polypropylene

Abstract: Isotactic polypropylene samples drawn at 20 and 100°C to a draw ratio 6 and 10 were annealed with free and fixed ends between 40 and 155°C for periods of time between 1 and 103 min. All the annealing effects proceeded farther with unclamped samples free to shrink than with clamped samples. The disorientation of crystal lattice and the shrinkage are extremely fast reaching saturation values characteristic for the temperature of annealing. At higher annealing temperature, one could observe merely the saturation values with the whole transition being completed in less than 1 min. The long period growth, the increase in density, and the intensity of small-angle X-ray scattering are linear functions of the logarithm of annealing time and hence persist with gradually decreasing rate long after the completion of disorientation and shrinkage. The observed effects can be well explained on the basis of the two-stage model of plastic deformation of crystalline polymers which assumes the formation of strong well-aligned microfibrils connected by interfibrillar tie molecules. Proben aus isotaktischem Polypropylen bei 20 und 100°C zu einem Dehnungsverhaltnis von 6 oder 10 verstreckt, wurden mit freien und festgehaltenen Enden zwischen 40 und 155°C fur verschieden lange Zeiten zwischen 1 und 103 Minuten getempert. Alle Tempereffekte sind ausgepragter fur Proben, die frei schrumpfen konnen, als fur Proben mit festgehaltenen Enden. Die Desorientierung des Kristallgitters und das Schrumpfen schreiten extrem rasch fort und erreichen in kurzer Zeit Sattigungswerte, die charakteristisch fur die Tempertemperatur sind. Bei hoheren Tempertemperaturen kann man nur noch die Sattigungswerte beobachten, da der ganze Vorgang in weniger als einer Minute beendet ist. Das Langperiodenwachstum, der Dichteanstieg und die Erhohung der Intensitat der Kleinwinkelstreuung sind dem Logarithmus der Temperzeit proportional. Deshalb dauern diese Effekte mit zwar stetig abfallender Steigung noch lange an, nachdem die Desorientierung und das Schrumpfen schon langst zu einem Stillstand gekommen sind. An Hand des Zweistufenmodells der plastischen Deformation von kristallinen Hochpolymeren, das die Bildung von zugfesten, gut orientierten und durch zwischenfibrillare Verbindungsmolekule verknupften Mikrofibrillen annimmt, konnen die Beobachtungen befriedigend gedeutet werden.

Diffusion Coefficient of So2 in Air

Abstract: (1971). Diffusion Coefficient of So2 in Air. Environmental Letters: Vol. 2, No. 1, pp. 13-21.

Mating Behavior and Evidence for a Sex Pheromone of Dioryctria abietella (Lepidoptera: Pyralidae (Phycitinae))

Abstract: Mating behavior of Dioryctria abietella (Denis & Schiffermuller) is described, and evidence of female production and male perception of a sex pheromone is presented. The nocturnal “calling” behavior of females at the time of sex-pheromone release was observed under light-dark cycles of 12 hours light: 12 hours darkness. Calling began 5–6 hours after dark, was maximum after 9 hours of darkness, and generally ceased just prior to the onset of the light phase. Matings occurred only during periods of female calling, and the peak periods of mating and female calling coincided. Multiple matings were observed with both male and female moths. A crude diethyl ether extract of female abdomens excised during peak periods of calling elicited initial mating responses in male moths when the extract was introduced into the air stream of an olfactometer.

Fluorimetric Determination of Nitrate

Abstract: A sensitive fluorimetric method has been developed for the determination of nitrate based on the reduction of nitrate to nitrite with hydrazine sulfate and the subsequent determination of the nitrite formed with 2, 3-diaminonaphthalene. Solvent effect on fluorescence intensity, optimum reaction conditions, and sensitivity of the method are discussed.

Salt rejection by polymer membranes in reverse osmosis. I. Nonionic polymers

Abstract: An attempt is made to analyze the relationship between salt rejection and water flux of nonionic polymer membranes in reverse osmosis on the basis of the movement of water in the membranes. The salt rejection Rs is a consequence of transport depletion of salt in relation to water flux. The transport depletion can be quantitatively expressed through knowledge of the mode of water transport and by application of free-volume theory to membrane transport phenomena. Water permeation can be characterized by a parameter ω = RTK1/P1v1, K1 denoting hydraulic permeability, P1 diffusive water permeability, v1 the molar volume of water. Thus polymer membranes can be classified in three categories: ω = 1 (diffusion membranes); ω > 1 (diffusion-flow membranes); and ω ≫ 1 (flow membranes). Salt rejection Rs can be expressed in terms of P1, the diffusive salt permeability P2, and the effective pressure (Δp − Δπ): Experimental results obtained with various hydrophilic polymers are presented as the dependence of Rs on the logarithm of water flux. Good agreement was found between the experimental data and the calculated curve. Excessive swelling of membranes results in bulk flow of water (high ω) with coupled transport of salt. Hence the salt rejection decreases quickly as water flux in creases beyond a threshold value above which water flux can be characterized as bulk flow.

Electron microscopy of drawn polypropylene

Abstract: Extremely thin polypropylene films formed by evaporation of dilute solutions floating on water, thin films deposited on Mylar or on carbon-coated Mylar, and bulk samples were deformed; after etching with aqua regia or chromic acid, the surfaces were studied by electron microscopy of surface replicas. At small draw ratio, microfibrils with lateral dimensions of about 200 A, originating in micronecks at crack boundaries of the original crystal lamellae, were obtained in isolated areas exhibiting maximum local strain separated by large regions of much less deformed material. With increasing draw ratio the necked regions grow, the old structure gradually being reduced to smaller and smaller islands until it disappears completely. The inhomogeneity of strain in adjacent bundles of microfibrils creates a great many longitudinal voids with more or less disoriented microfibrils bridging the gaps. The regular arrangement of crystalline blocks of rather uniform length and width can be occasionally seen on surface replicas of drawn samples, and much better on dark-field electron micrographs of drawn and annealed thin membranes. In the latter case the blocks are very uniform and have similar dimensions along and perpendicular to the axis of the microfibril. The evidence from the electron micrographs, together with previous small-angle x-ray scattering data, supports Peterlin's molecular model for plastic deformation of crystalline polymers.

Crystallite size in highly drawn polyethylene

Abstract: The size and distortion of crystallites in samples of linear polyethylene were determined before and after plastic deformation. A slowly cooled sample, a quenched sample, and highly drawn films (draw ratio 16) were investigated by different methods. Wide-angle x-ray patterns were analyzed to study the average size of the crystalline mosaic blocks and their distortion. In addition, the longitudinal crystal thickness (in the chain direction) was evaluated by two other approaches, determination of the long period, and the melting temperature of irradiated samples. The results show clearly that the size of the crystalline mosaic blocks changes substantially with drawing of polyethylene. Not only is the lateral crystal thickness affected, but the longitudinal crystal dimensions also change during the drawing process. By the three independent methods we find that the longitudinal crystal thickness after drawing is independent of the value for the undrawn samples, as was reported earlier by Peterlin. The change in crystallite size after drawing is accompanied by a large decrease in crystal volume to about 10% of the value for the undrawn sample. The degree of distortion in the crystals seems not to be affected by the deformation process. These experimental data can be considered evidence for high chain mobility and for the possibility of rearrangement of chain molecules during the process of plastic deformation.

NMR observations of drawn polymers. VII. Nylon 66 fibers

Abstract: Wide-line NMR spectra have been obtained on an oriented sample of drawn nylon 66 fibers at temperatures between −196°C and 200°C and at alignment angles between the fiber axis and the magnetic field of 0°, 45°, and 90°. At −196°C, 20°C, and 180°C, the complete angle dependence of the NMR spectrum has been measured. The second moments of these spectra have been compared to theoretical second moments calculated for various models of chain segmental motion in an attempt to elucidate the mechanisms involved in the low-temperature segmental motion (γ process) and the high-temperature segmental motion (αc process). In agreement with earlier suggestions, the present results indicate that the γ process consists of segmental motion in noncrystalline regions. The overall decrease in second moment caused by the γ process is consistent with a model in which all noncrystalline segments rotate around axes nearly fixed in space. Furthermore, this decrease shows a pronounced dependence on the alignment angle. It is believed that this is due to tie molecules which become highly oriented along the fiber axis during drawing; their axes of rotation will therefore be nearly parallel to the fiber axis. The segments in noncrystalline entities such as chain folds and chain ends are less well oriented along the fiber axis and make an essentially isotropic contribution to the second moment decrease. The second moment at 180°C indicates the presence of considerable motion in the crystalline regions, and this motion is denoted the αc process. The second moment Sc of the crystalline regions is strongly dependent on the alignment angle, the predominant feature being a relatively high value of the second moment when the fiber axis is directed parallel to the magnetic field. This is in qualitative, but not quantitative, agreement with the motional model recently advanced by McMahon, which assumes full rotation of the chains around their axes. Excellent quantitative agreement with experiment has been obtained by superimposition of rotational oscillation around the chain axis of amplitude roughtly 50°, and torsion of the chains with neighboring CH2 groups oscillating around the CC bond with a relative amplitude of about 40°. A model in which the chains perform rotational jumps of 60° between two equilibrium sites has also been considered (60° flip-flop motion). A distinction between this model and rotational oscillation has not been possible.

Ionic membranes for water desalination. I. Charge mosaic membranes from blends of random copolymers

Abstract: The incompatibility of polymers was used in order to prepare films with regular phase separation. The conversion of the separate phases into polyelectrolytes of different charge should lead to the preparation of charge mosaic membranes for piezodialysis. Copolymers of suitable monomers with 20–45 mole-% butadiene content were synthesized which could be cross-linked with sulfur monochloride. The comonomers were: styrene, 2-vinyl pyridine, 4-vinyl pyridine, methacrylic acid, methyl methacrylate and 2-chloroethyl methacrylate. After conversion into the ionic form cross-linked films of these copolymers showed salt rejections in the range of 26–78 % and water permeabilities of 40–43 [1· mm· m−2· day−1], respectively. These films can be used as anion and cation exchange membranes for water desalination. Mixtures of poly (2-vinyl pyridine-co-butadiene) and poly (styrene-co-butadiene) yielded films with regular phase separation. After cross-linking and conversion into the ionic form these charge mosaic membranes were porous and had poor mechanical strength. Despite these unfavourable properties a salt enrichment of 4.8 % was found in one case. Die Unvertraglichkeit von Polymeren wurde benutzt, um Filme mit regelmasiger Phasentrennung herzustellen. Die Umwandlung der einzelnen Phasen in Polyelektrolyte entgegengesetzter Ladung sollte die Darstellung von „Charge Mosaic” Membranen fur die Piezodialyse ermoglichen. Es Wurden Copolymere geeigneter Monomerer mit 20–45 Mol-% Butadien hergestellt, die mit Schwefelchlorid vernetzt werden konnten. Die Commonomeren waren: Styrol, 2-Vinylpyridin, 4-Vinylpyridin, Methacrylsaure, Methylmethacrylat und 2-Chlorathylmethacrylat. Vernetzte Filme dieser Copolymeren zeigten nach der Umwandlung in die ionische Form eine Salzabweisung von 26–78 % bei einem Wasserdurchflus von 40–43 [1 · mm · m−2 · Tag−1]. Diese Filme konnen als Anionen- und Kationenaustauscher-Membranen fur die Wasserentsalzung verwendet werden. Mischungen von Poly(2-vinylpyridin-co-butadien) und Poly (styro1-co-butadien) ergaben Filme mit regelmasiger Phasentrennung. Die „Charge Mosaic” Membranen, die nach der Umwandlung der vernetzten Filme in die ionische Form erhalten wurden, waren poros und hatten eine geringe Festigkeit. Trotz dieser ungunstigen Eigenschaften wurde in einem Fall eine Salzanreicherung von 4,8 % gefunden.