Infrared and raman studies on the phase structure of barium ethyl(octyl)phosphate-water system

Barium ethyl(alkyl)phosphates, as new simple surfactants ((C₂H₅O)(RO)-PO ₂ ^– )₂Ba²⁺ with various chain length ofR, were synthesized. The infrared spectra in the CH stretching region were measured for these surfactants in the solid state and in aqueous solution, and assignments were made. In particular, the ordering and environment of octyl chains in the different phases of the barium ethyl(octyl)phosphate-water system were studied by the Fourier-transform-infrared and Raman spectra. The CH stretching bands in the infrared spectra reflected the ordering and environment of octyl chains in each phase. The Raman band connected to the PO ₂ ^– symmetric stretching mode was sensitively shifted. This was caused by the change of aggregation structures with different Ba²⁺...PO ₂ ^– interaction. The infrared band arising from the PO ₂ ^– antisymmetric stretching mode was insensitive to the phase structures. The C–C stretching region in the infrared spectra was used to discuss the ordering of each phase.     

Characterization of p-hydroxybenzoic acid methylester physi- and chemiadsorbates on silica by IR and UV-spectroscopy

Physiadsorbates and chemiadsorbates of p-hydroxybenzoic acid methylester (pHBAME) on colloidal and porous silicas were studied by IR and UV spectroscopy. In the IR spectra of self-supporting discs of the adsorbates, typical features were detected which allow differentiation between the physi- and the chemiadsorbed state: a strong absorption band at 1417 cm^–1 characterizes the chemiabsorbate. Dehydration by annealing and rehydration of the adsorbates proceeded also in a different way, indicated by absorption bands both in the carbonyl group and in the ring vibration frequency range. In the UV spectra the absorption maximum of the chemiadsorbate occured at 250 nm and that of the physiadsorbate at 255.5 nm (from cyclohexane suspensions of the adsorbates).Dedicated to Prof. Dr. Paul Heinz List on the occasion of his 65^th birthday.     

Investigations of the influence on the phase morphology of PP-EPDM-blends on their mechanical properties

This work covers the dependence of the mechanical properties of polymer blends on their composition and their phase morphology. Blends of EPDM-elastomers and polypropylene were prepared covering the whole concentration range. The phase morphology was varied strongly by employing different mixing techniques and its morphology was characterized by means of electron microscopy and light microscopy, as well as by x-ray scattering and calorimetry.Mechanical properties such as the complex shear modulus, the tensile modulus as well as the stress strain behavior were investigated as a function of the composition of the blends and their phase morphology. The experimental finding is that the complex modulus, the tensile modulus, the yield stress, and the ultimate stress are rather insensitive with respect to the phase morphology and vary continuosly with the composition. The elongation at break, on the other hand, as well as the impact strength were found to depend on the phase morphology and to vary discontinously with the composition. One conclusion to be drawn is that one is not always forced to control the phase morphology tightly during processing in order to obtain materials with sufficiently good mechanical properties. Rather, simple theoretical approaches, neglecting details of the phase morphology are frequently able to satisfactorily predict mechanical properties of multiphase blends.     

Mechanism of the grafting of organosilanes on mineral surfaces. IV. Phenylderivatives of sepiolite and poly (organosiloxanes)

Grafting reactions of phenyl groups on silica substrates using as reagents various phenylsilanes with variable distances between the silicon atoms and the aromatic ring by 0, 1, and 2 methylene groups [Si–(CH₂) _n –C₆H₅] were studied. Two different silicates have been selected as source of silica: sepiolite and tetraethyl-orthosilicate (TEOS). Sulfonic- and nitro-derivatives prepared from these phenyl compounds by electrophilic substitution reactions, have been obtained. The mechanism of these processes has been studied in relation to the number of methylene separating groups belonging to the starting reagents. The characterization of such systems has been achieved by XRD,²⁹Si and¹³C NMR/MAS, IR, and laser microprobe mass spectrometry.Parts I, II and III published in this Journal (1978) 256:135–139, (1979) 257:178–181 and (1985) 263:1025–1030     

Electrically conducting,thermally stable,and mechanically strong CuS-poly(parabanic acid) composite films and their shielding effect of electromagnetic wave

Poly(parabanic acid)-CuS composite film (wt-% of CuS=20–50) prepared by using organosol of CuS (=1500 Å) showed electrical conductivity of 0.1–70 S cm^–1, high thermal stability up to 250°C, high mechanical strength (breaking stress=7.0–12 × 10⁷ Pa), and good shielding effect of electromagnetic wave.     

Deformation behavior of oriented UHMW-PE fibers

The mechanical behavior of gel-spun, ultra-drawn, UHMW-PE fibers was investigated as a function of temperature, stress, and time under static and dynamic loading conditions. From a phenomenological point of view, two separate contributions to the deformation behavior could be distinguished, i.e., a reversible (viscoelastic) contribution and an irreversible plastic flow component. It was investigated whether or not this distinction can be rationalized on a molecular basis. The fibers were studied using static (creep) and dynamic mechanical analysis (DMA), dilatometry, and wide-angle x-ray scattering (WAXS). The results of the combined experimental observations are discussed in an attempt to relate the deformation behavior of highly oriented PE fibers to events occurring on a molecular scale.     

Charge-transfer interaction of some pyridinium salts with hen egg-white lysozyme

The charge-transfer interaction of pyridinium salts with lysozyme and L-tryptophan has been investigated by visible absorption, circular dichroism and fluorescence spectroscopy. Four quaternized and substituted pyridinium salts were used as electron acceptors. L-tryptophan was used as a model compound of electron donor for the purpose of the comparison with lysozyme. The binding constants obtained from absorption and circular dichroism spectra were 2.0–13 M^–1 and the sequence of the magnitude was found as EPCl(1-ethylpyridinium chloride) < MPCl(1-methylpyridinium chloride) < MNCl(1-methylnicotinamide chloride) < MNMCl(1-methyl-3-carbomethoxypyridinium chloride), which could be explained by the electron affinity of the pyridinium salt. The fluorescence spectra of lysozyme and L-tryptophan in the absence and presence of pyridinium salts were interpreted by Stern-Volmer plot. The static constants thus determined were in agreement with the binding constants obtained by other methods.     

Melittin and ionic surfactant interactions in monomolecular films

The interaction between the anionic and cationic surfactants with Melittin spread monolayers at the air-water interface was investigated. The addition of anionic Cl^–, under the films of Melittin gives rise to a change in both surface pressure and surface potential. These interactions are different when surfactants are present, due to specific interactions between Melittin and the ionic-surfactants.     

Spectrophotometric behavior of polyvinylpyrrolidone in aqueous and nonaqueous media (I)

Electronic spectral behavior of polyvinylpyrrolidone solutions in various media has been determined by UV-VIS spectrophotometry. A theoretical approach has been developed to explain the experimentally observed concentration dependent spectral behavior of polyvinyl pyrrolidone in aqueous and nonaqueous solvents. Increase in the concentration of the polymer or the addition of guanidine salts caused bathochromic shift. A similar concentration effect has been observed in nonaqueous media in the absence of guanidine salts.     

On Tanaka-Fillmore's kinetics swelling of gels

Tanaka and Fillmore treated the swelling of a gel as a process where a crosslinked polymer network having been initially under uniform stress is expanded by osmotic pressure, sucking up the surrounding fluid medium. We point out that their physical reasoning is unnatural and leads to an unacceptable conclusion; we propose a more sound approach to the same problem. Our treatment assumes that the gel network is extended not by the osmotic pressure of the gel, but rather by the swelling pressure which is generated by the excess fluid penetrating in against the real nature of a polymer network that tends to shrink. The diffusion equation of the fluid, hence, plays a dominant role and gives the distribution of fluid concentration in contrast to Tanaka-Fillmore's scheme. The expression for the distribution of local strain in a spherical gel is deduced from the relation of mechanical balance between two forces, the one is due to the elasticity of the network and the other due to the gradient in the chemical potential of the fluid. The results obtained have forms analytically similar to Tanaka-Fillmore's, but are differ in the physical meanings.     

Solubilization of oleyl alcohol by pure and mixtures of surfactants

The solubilization behavior of oleyl alcohol by pure and mixtures of surfactants systems have been studied in terms of the maximum additive concentration (MAC), the solubilizing power, and the particle sizes of micelles with or without oleyl alcohol. The surfactants used are amphoteric (N,N-dimethyl-N-lauroyl lysine, DMLL; N,N,N-trimethyl-N-lauroyl lysine, TMLL; N,N-dimethyl-N-(carboxymethyl)-lauryl ammonium, DMCL), anionic (sodium dodecyl sulfate, SDS) and nonionic (alkyl polyoxyethylene ethers).The maximum additive concentration of oleyl alcohol by pure surfactants is larger by nonionic surfactants than by others.For a nonionic surfactant system mixed with DMLL, the mixing effect of surfactant on the increase in the MAC is not recognized. While, for DMLL mixed with SDS, the MAC becomes larger than that by pure surfactants. This may be attributed to the fact that the large micellar size will result in increasing the maximum additive concentration.     

Spinodal decomposition of the polymer blend deutereous polystyrene (d-PS) and polyvinylmethylether (PVME) studied with high resolution neutron small angle scattering

Decomposition of a polymer blend in the miscibility gap has been studied by small angle scattering of neutrons, using a double crystal diffractometer. It covers a range of 10^–5 to 10^–3 Å^–1, which connects the region of elastic light scattering and, at the upper end, the region of conventional neutron small angle scattering instruments. The decomposed structure in the miscibility gap can be described by a characteristic lengthR which increases with time,t ^1/3 between 7 and 25 min. At longer times, the growth follows a more linear power law. This behaviour is consistent with predictions of the domain growth for liquid mixtures and is estimated by using the self diffusion constant, viscosity, and the surface energy of the polymer.on leave ESFM-IPN Mexico     

Strength of fibers from wholly aromatic polyesters

A theory of the strength (or the tenacity) of highly oriented Liquid Crystal Polymer (LCP) fibers was developed, and its results were compared with existing tensile strength data of fibers of a copolymer of 1,4-oxybenzoate and 6,2-oxynaphthoate. A basic premise of the theory is that the mechanical load transfer between polymer chains is through intermolecular interaction which acts in a manner similar to that of shear stress, and that the fiber strength is primarily governed by the intermolecular adhesion strength. The theory also incorporates the effects of MW, MW distribution, and the chain orientation distribution. Analysis of the experimental tenacity data demonstrates that the present theory can quantitatively describe the variation of the tenacity of LCP fibers with MW both in the as-spun and in the heat-treated states. The theory further predicts that the predominant factor governing the tenacity of LCP fibers is primarily due to MW increase due to solid-state polymerization. It is also demonstrated that the intermolecular adhesion between LCP chains is relatively weak and does not improve with heat treatment. The absence of factors that limit the MW increase (i.e, imbalanced end-groups and side reactions of end groups) is a prerequisite for fast heat treatment of a LCP fiber to a high tenacity.Symbols A _f the cross-sectional area of a single polymer chain - E _f the theoretical modulus of a polymer chain - G _m the shear modulus of fiber - h(l) the chain length distribution function - l the chain length - l the number average chain length - l _c the length of chain units that are bonded to adjacent polymer chains - n ² 4G _m/CE_f - N _c the number of polymer chains per unit area perpendicular to the fiber axis - P _b the probability that a chain does not have a chain end in the fracture zone - P _e the probability that a chain has, at least, a chain end in the fracture zone - q _e,q _b the probability of finding an ending and a bridging polymer chain, respectively, in the fracture zone - l the length of fracture zone - the elongation of a polymer chain - the chain orientation angle - _f the normal stress that acts on a polymer chain - _fu the fiber tenacity - _e the shear stress that acts on a polymer chain surface Dedicated to Prof. Dr. rer. nat. Wolfgang Hilger, Chairman of Hoechst A.G. in honor of his 60th birthday     

Experimental results for the L3 phase in a zwitterionic surfactant system and their implications regarding structures

Conditions for existence of the L₃ phase have been determined for a system containing water, n-hexanol, and the zwitterionic surfactant n-tetradecyldimethylamineoxide. Electric birefringence, light-scattering, rheology, and electrical-conductivity experiments were performed on this phase. Results are consistent with the existence of platelike micelles, whose diameter changes with surfactant concentration in such a way that it remains comparable to mean plate spacing. This behavior can be understood in terms of a previous L₃ phase theory containing randomly oriented plates.on leave from Rice University, Texas, USA     

Spectral studies on the structure and monovalent cation binding to poly(1,3-propylene phosphate) — a synthetic analogue of natural teichoic acids

A poly(1,3-propylene phosphate), (PPP), which can be considered as a synthetic analogue of naturally occurring teichoic acids, has been studied with infrared spectroscopy. Infrared spectra of PPP in acidic and alkali metal forms have been analyzed in detail and the conclusions concerning intermolecular interactions between phosphate diester groups and the monovalent cation binding to PPP of a different degree of polymerization (n) have been drawn out. It has been shown that in anhydrous PPP, acidic groups are extensively hydrogen bonded. The process of association of phosphate diester groups is rather complex, especially in the samples of lowern. The role of H-bonds in some solution properties of high-molecular PPP samples has been discussed.     

The association of urethane-polyethyleneoxide (HEUR) thickeners,as studied by NMR self-diffusion measurements

The concentration and molecular weight dependence of the self-diffusion coefficient (D _self) of associative polymers of HEUR-type in aqueous solution have been investigated using FT-PGSE-NMR technique. The idea of three-dimensional network formation as a result of aggregation of the hydrophobic end-groups of the polymer in junctions is supported through the observed dramatic lowering ofD _self with increased concentration. The network-formation efficiency depends on the polymer molecular weight as well as the hydrophobicity of the end-groups.A double logarithmic dependence of the self-diffusion coefficient versus concentration (c) has been observed:D _selfc ^–a1,a2 . The first exponent,a ₁, is valid at low concentration, <1% polymer per weight solution, and ranges from 0.5 to 1, whereas the second exponent,a ₂, describing systems of higher concentration, ranges from 2 to 2.7.     

The viscoelasticity of spinnable solutions of alkyltrimethylammonium salicylates

The viscoelasticity has been measured for aqueous solutions of tetradecyl-and hexadecyltrimethylammonium salicylates (C₁₄TASal, C₁₆TASal). The aqueous solutions of C₁₄TASal without salt displayed the gel-like behavior at 10.0×10^–2 g cm^–3, but those more dilute than 3.2×10^–2 g cm^–3 presented the viscoelasticity similar to that of a Maxwell liquid. The Maxwell-like behavior was converted to the polymer-like one on the addition of (0.1–0.2) M NaBr or (0.02–0.2) M NaSal. The gel-like viscoelasticity can be connected with the spinnability of cohesive fracture failure, and the Maxwell-like and polymer-like viscoelasticities are concerned with the spinnability of ductile failure. The gel-like and Maxwell-like viscoelasticities originate in the pseudo-network formed by the pseudo-linkages between rodlike micelles, while the polymer-like viscoelasticity is caused by the entanglement of long rodlike micelles in semidilute and concentrated solutions. The aqueous solutions of C₁₆TASal behaved very similar to those of C₁₄TASal.     

Precipitation of surfactant salts III. Metal perfluoroalkanecarboxylates

Precipitation of perfluorocarboxylic acids (n-C₃H₇OOH, n-C₇H₁₅COOH, and n-C₉F₁₉COOH) in aqueous solutions of different metal nitrates (K⁺, Ag⁺, Ca²⁺, Ba²⁺, Zn²⁺, Al³⁺, La³⁺) was studied by solubility and calorimetric measurements. The free energy of precipitation per single surfactant chain was found to depend on the chain length but not on the charge of the reacting cation. It was shown that the precipitation of perfluorocarboxylates of multivalent cations was governed by positive entropy change and a low enthalpic contribution, whereas the soaps of monovalent cations exhibited the opposite behavior. The entropy of precipitation was not affected by the chain length of the surfactants in the presence of monovalent cations, but it increased for cations of higher charge.Supported by the NSF Grant CHE-8619509.This paper is dedicated to Professor Armin Weiss on the occasion of his 60th birthday. One of the authors (E. M.) particularly appreciates many years of cooperation with Professor Weiss in editing Colloid and Polymer Science, as well as in many other scientific interactions.     

Effect of plasticizer concentration on the hysteresis,tear strength and stress-relaxation characteristics of black-loaded rubber vulcanizate

The effect of plasticizer concentration on the stress softening, tear strength and stress relaxation of black loaded bromobutyl rubber vulcanizate has been investigated. The stress softening in the rubber vulcanizate, an energy dissipative process at higher strain, may be explained primarily by changes that take place in the rubber phase of the filled vulcanizate. Increased plasticizer concentration leads to decrease in the equilibrium hysteresis. A quantitative relationship between energy density and hysteresis has been derived, which is applicable at and below the elongation at break. Increase in plasticizer concentration results in decrease in the effective diameter of the tip of the tear, which in turn decreases the tear strength. Rate of relaxation decreases with increase in the plasticizer concentration in the carbon-black-filled vulcanizate.     

Relation between syneresis and rheological properties of particle gels

The relation between the tendency to exhibit syneresis of rennet (pH 6.65) and acid (pH 4.6) skim-milk gels and the rheological properties of these gels is discussed. Based on the syneresis model for milk gels of Van Dijk and Walstra [1, 4, 14, 19] it is reasoned that the average lifetime of the protein-protein bonds in the casein strands forming the gel network, the fracture force of these strands, and their flexibility are the main mechanical properties of importance. It is argued that the ratio of the loss modulus to the storage modulus (tan δ) as a function of the time scale of the measurement in dynamic experiments is a good measure of the first property. Results are given for rennet skim-milk gels at 25, 30, and 40°C and for an acid skim-milk gel at 30°C. Moreover, the stress strain relation and fracture behavior of both gels were assessed in creep measurements as a function of the duration of the applied stress. Rennet skim-milk gels have a lower fracture stress σ _f and therefore probably a lower fracture force per strand and a higher tan δ over long time periods than acid gels, while tan δ increases with temperature. As predicted, low fracture stresses and high tan δ correlated with an increased tendency to exhibit syneresis.