Rigid-rod polymers with flexible side chains

Modeling studies were performed for a rigid-rod polyester with hexadecyloxy side chains (n=16) in order to simulate x-ray scattering curves in the medium angle scattering region (s=4 sin / from 0.2 Å^–1 to 2.2 Å^=t–1). The experimental ones were taken from a material obtained by cooling to room temeperature from the smectic mesophase at 150°C. The wide-angle x-ray diffractograms were calculated for given conformations and molecular arrangements using Debye's equation. The theoretical result thus obtained for a great variety of possible packing models and structures was compared to the experimental result. The size of the effective scattering region is found to be 61×18×52=6×10⁴ ų and consists of approximately five layers, each of which is composed of two rigid rods and 20 side chains. The planes form by the rigid rods, together with the side chains, have a distance of 3.6 Å, the distance between the rods being 26 Å. As the main result, it was found that the side chains form regions with a denser ordering (clustering). The interchain distance for side chains decreases in the regions from 5.3 Å to 4.8 Å.     

Determination of the structure factor for concentrated silica dispersions using small angle x-ray scattering. II. Experiment

The structure factor of a number of silica suspensions in cyclohexane, with concentrations ranging from 0.01 to 0.714 gcm^–3, has been determined with small angle x-ray scattering, using a Kratky camera. The experimental structure factor is compared with a theoretical one for which polydispersity effects on the particle scattering factor and on the structure are explicitly taken into account.Analysis of the scattered intensity at a scattering angle=0 shows that the particles in the suspension interact like hard spheres, with a specific hard sphere volume of 0.61 cm³g^–1. A comparison of the experimentally determined structure factor with the structure factor found by a model calculation for a polydisperse system, using the experimental particle size distribution, showed a general agreement. The height of the first maximum agreed well for all concentrations, however its position varied stronger with concentration in the experimental curves. A possible explanation of this effect is given.     

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.     

Electrical properties of poly(bis(β-phenoxyethoxy)phosphazene) and its complexes

Electrical and dielectrical properties of poly(bis(-phenoxyethoxy)phosphazene) (I) and its complexes with various content ratios of AgSO₃CF₃ to monomeric unit (0.25/1 (II) and 0.5/1 (III) in molar ratio) were investigated.Dc conductivity of respective samples at 18 °C were 6.1×10^–12, 4.4×10^–9, and 7.1×10^–8 S/m.Dc conduction was considered to be due to ion hopping. Charge mobility ranged from 3×10^–12 to 6× 10^–11 m²/Vs depending on the applied field in sample II. In sample I, a tan peak was found which can be ascribed to molecular relaxation of main chains. The peak vanished upon introducing AgSO₃ CF₃. Temperature dependence of total conductivity ( _T ) measured byac method in the temperature range between –150 °C and 50 °C showed several peaks at the temperatures corresponding to the peak temperatures of tan. Total conductivities of respective samples at 100 kHz were 4.9×10^–7 (69 °C), 1.7×10^–4 (45 °C), and 1.5×10^–4(40°C)S/m.     

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.     

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.     

Formation of uniform silver particles from bis (1,2-ethanediamine)silver(I) complex

Uniform spherical silver particles were produced by decomposing the bis(1,2-ethanediamine)silver(I) complex, by aging a solution of 1.0×10^–3 mole dm^–3 in silver (I) nitrate, 1.0 mole dm^–3 in 1,2-ethanediamine, and 2.5×10^–1 mole dm^–3 in nitric acid (basic solution) at 100°C for 42 min. The average modal diameter was estimated to be 0.52 m with a relative standard deviation of 0.10. A moderately oxygenrich layer, 40 Å thick, on the surface of the particles was detected by means of photoelectron surface microanalysis (XPS). The silver particles grew through a polynuclear-layer mechanism, as judged from the concentration change in soluble silver(I) species in the supernatant solution. The particles' point of zero charge (PZC) was estimated at pH 6.5 by potentiometric titration.     

The influence of surfactants on latex flocculation with poly(diallyldimethyl ammonium chloride)

Aqueous latex was flocculated by mixtures of poly(diallyldimethyl ammonium chloride), PDADMAC, and anionic surfactants. Sodium dodecyl sulfate, (SDS), and Aerosol OT influenced flocculation whereas nonionic Tergitol NP-10 did not. The flocculation domains were correlated with properties of the polymer-surfactant complexFlocculation was never observed above the CMC of the corresponding surfactant solution without polymer or latex. At SDS concentrations greater than 10^–3.6 M the flocculation boundary corresponded to the first appearance of insoluble polymer-surfactant complex which was characterized by dynamic light scattering and microelectrophoresis. Under these conditions latex (diameter 570 nm) and dispersed polymer-surfactant complex particles (diameters between 30 and 2 000 nm) displayed simultaneous homo and heteroflocculation. The boundaries of the flocculation domains at low surfactant concentration were determined by the ratio of polymer to latex and by the net electrostatic charge of the soluble polymer-surfactant complex. On the other hand, the mechanisms controlling flocculation boundaries in the dispersed polymer-surfactant domain require further clarification.     

Characterization of water-soluble,cationic polyelectrolytes as exemplified by poly(acrylamide-co-trimethylammoniumethylethacryate chloride) and the establishment of structure-property relationships

The cationic copolymerization products of poly (acrylamide-co-trimethylammoniumethylmethacrylate chloride (PTMAC) having cationic monomer percentages of 8%, 25%, and 50% as well as the cationic homopolymer, were characterized with respect to their molecular dimensions. The light-scattering and viscometric measurements were carried out for molecular weights ranging from 200 000 to 12 800 000 g/mol in 1 M NaCl solution at 25°C. It was possible to establish a relationship between the molecular weight and the two parameters: intrinsic viscosity and radius of gyration, for all four polymers.Rheological investigations of the flow properties in 1 M NaCl solution were also carried out using the polymer with a cationic monomer of 50% (PTMAC 50). Structure-property relationships were formulated which made it possible to describe and predict the shear viscosity, both in the zero-shear region (Newtonian region) and in the shear-dependent region (non-Newtonian region) as a function of the polymer concentration, the molecular weight, and shear rate.Abbreviations a exponent of the []-M relationship - A ₂ 2^nd virial coefficient/mol·cm³·g^–2 - AAm acrylamide - b slope of the flow-curve in the shear-rate dependent region - c concentration/g·cm^–3 - dn/dc refractive index increment/cm³·g^–1 - f function - K constant of the []-M relationship/cm³·g^t-1 - m _c proportion of cationic monomers/mol % - M molecular weight/g·mol^–1 - M _w weight-average molecular weight/g·mol^–1 - M _n number-average molecular weight/g·mol^–1 - NaCL sodium chloride - PAAm polyacrylamide - PS polystyrene - PTMAC poly(acrylamide-co-trimethylammoniumethylme thacrylate chloride) - R_G ^20.5 radius of gyration/nm - TMAC trimethylammoniumethylmethacrylate chloride - shear rate/s^–1 - critical shear rate/s^–1 - viscosity/Pa·s - 0 zero-shear viscosity/Pa·s - _s solvent viscosity/Pa·s - _sp specific viscosity - [] intrinsic viscosity/cm³·g^–1 - relaxation time/s     

Secondary structural changes of chymotrypsinogen A,alpha-chymotrypsin,and the isolated polypeptides Cys1-Leu13, Ile16-Tyr146, and Ala149-Asn245 in sodium dodecyl sulfate,urea and guanidine hydrochloride

Secondary structural changes of chymotrypsinogen A,-chymotrypsin, and their isolated polypeptides Cys¹-Leu¹³, Ile¹⁶-Tyr¹⁴⁶, and Ala¹⁴⁹-Asn²⁴⁵were examined in aqueous solutions of sodium dodecyl sulfate (SDS), urea, and guanidine hydrochloride (residue numbers from chymotrypsinogen). After the fragmentation by the cleavage of disulfide bridges in-chymotrypsin, the helical structure was formed in the isolated polypeptide 16–146 where the helical segments do not exist in the protein state. The polypeptide 149–245, where the helical segments of the parent protein are originally located, contained no helices. The polypeptide 1–13 was almost disordered. The three polypeptides, chymotrypsinogen,-chymotrypsin and the polypeptide 16–146, clearly showed differences in the stabilities of helical structures in solutions of urea and guanidine hydrochloride. The addition of SDS accelerated the formation of helical structures in each polypeptide except for 1–13.     

Compression studies on aqueous polystyrene latices

An apparatus, that allows simultaneous measurements to be made of excess osmotic pressure and optical diffraction of polymer colloid dispersions, has been constructed. Results are reported for monodisperse polystyrene latices at several salt concentrations. An interesting feature of the results is a clear indication of a co-existence region occurring with particles of 182 nm diameter in sodium chloride concentrations of 10^–4 mol dm^–3     

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     

New organosols of ZnS and HgS in N,N-dimethylformamide and dimethyl sulfoxide. Use in the preparation of semiconductive polymer-metal sulfide composite films

Organosols of ZnS and HgS in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) were prepared by reaction of Zn and Hg salts with H₂S. ZnS in the DMF organosol has a particle size of about 300 Å, determined by an argon laser scattering technique. The form of HgS in the organosols varies with temperature, concentration of HgS, and type of solvent;-HgS in a DMF organosol is converted into-HgS at –30 °C or above. Poly(acrylonitrile)-ZnS or -HgS composite films prepared from organosols are semiconductive, and the electrical conductivity of the film increases by a factor of 10²–10³ on exposure to moisture or alcohol vapour. Poly(acrylonitrile)--HgS composite films, prepared from heated-HgS, show electrical conductivity of a range of 10^–1–10^–2 S cm^–1 and a large electron mobility.     

Dielectric relaxation of specially prepared polystyrene terminated with rigid polar groups

Two polystyrenes terminated withp-cyanobenzyl andp-cyanobiphenyl groups (=labels) were prepared and their complex dielectric constants were measured in the glass transition region in the frequency range 10^–2–10⁶ Hz. The glass temperaturesT _g (DSC) were considerably different, 92 and 97.5°C, resp., although their molecular weights were very similar (11 000 and 10 000 g/mol, resp.). Their relaxation behavior showed that the cyano groups relax cooperatively with the polymer segments. The cyanophenyl groups were found to relax with shorter relaxation times than the cyanobiphenyl groups. The measured relaxation strengths showed that there was no association between the dipoles. The relaxation mechanisms of the cyano groups in both labels seemed to be different although the only difference between them was an additional phenyl group in the case of the second label.     

Prediction of the non-Newtonian viscosity and shear stability of polymer solutions

The structure-property relationships derived here permit the prediction of both the zero-shear viscosity ₀, as well as the shear rate dependent viscosity . Using this molecular modeling it is now possible to predict over the whole concentration range, independently of the molecular weight, polymer concentration and imposed shear rate. However, the widely accepted concept: dilute — concentrated, is insufficient. Moreover it is necessary to take five distinct states of solution into account if the viscous behavior of polymeric liquids is to be described satisfactorily. For non-homogeneous, semi-dilute (moderately concentrated) solutions the slope in the linear region of the flow curve (= must be standardized against the overlap parameterc · []. As with the ₀-M-c-relationship, a-M -c- relationship can now be formulated for the complete range of concentration and molecular weight. Furthermore, it is possible to predict the onset of shear induced degradation of polymeric liquids subjected to a laminar velocity field on the basis of molecular modeling. These theoretically obtained results lead to the previously made ad hoc conclusion (Kulicke, Porter [32]) that, experimentally, it is not possible to detect the second Newtonian region.Roman and Italian symbols a exponent of the Mark-Houwink relationship - b exponent of the third term of the ₀-M -c relationship - c concentration /g · cm^–3 - E number of entanglements per molecule - F(r) connector tension - f function - G _i ^A shear modulus; A indicates that it /Pa has been evaluated by a transient shear flow experiment; i is the shear rate to whichG ^A refers to - G storage modulus /Pa - G _p plateau modulus /Pa - H() relaxation spectrum /Pa - h shift factor (₀/_r) - K _H Huggins constant - K _b third constant of the ₀-M -c relationship - K constant of the Mark-Houwink relationship - M molecular weight /g · mol^–1 - M _e molecular weight between two /g · mol^–1 entanglement couplings - N number of segments per molecule - n slope in the power-law region of the flow curve - p p-th mode of the relaxation time spectrum - R gas constant /8.314 J·K^–1·mol^–1 - r direction vector - T temperature /K Greek symbols ß reduced shear rate - shear rate /s^–1 - shear viscosity /Pa·s - _s solvent viscosity /Pa·s - _sp specific viscosity - ₀ zero-shear viscosity /Pa·s - apparent viscosity at shear rate - reduced viscosity - viscosity of polymeric liquid in /Pa·s the second Newtonian region - [] intrinsic viscosity/cm³·g^–1 - screening length/m - /g·cm ^–3 density - relaxation time/s - ₀ experimentally derived relaxation time/s - angular frequency of oscillation Indices conc concentrated - corr slope corrected - cr critical - deg degradation - e entanglement - exp experimental - mod moderately concentrated/semi-dilute - n number average - p polymer - R Rouse - rep reptation - s solvent - sp specific - theo theoretical - weight average - relaxation time - o experimental or steady state - * critical - ** transition moderately conc. — conc. - + transition dilute — moderately cone. Paper presented at the 2nd bilateral U.S.-West German Polymer Symposium, Yountville, the 7th–11th September 1987.     

Kinetics of adsorption and desorption of sodium alkyl sulfates to and from nylon particles

The desorption rate of surfactant ions from nylon particles was investigated at the concentrations below the critical micelle concentration by applying the stopped-flow method. A mixing cell of stopped-flow spectrophotometer was modified with platinum electrodes for electric conductivity detection. The change in electric conductivity with time in the desorption process was monitored by a memory-recorder system. The surfactants used were sodium decyl, sodium dodecyl, sodium tetradecyl, and sodium hexadecyl sulfates. The desorption rate was independent of the surfactant concentration and the rate constants were obtained by applying the first-order reaction scheme. The adsorption rate constants were estimated from the experimental desorption rate constants and equilibrium constants assuming the second-order kinetics. The desorption rate constants were determined to be 1–6 sec^–1 and the adsorption rate constants to be 2–8×10⁴ mol^–1 dm³ sec^–1; the former decreased and the latter increased with increasing number of carbon atoms in alkyl chain of the surfactants.     

New conducting polymers, 3. Doping,stability, electrical,and optical characteristics of poly-(P-phenylphosphoethynediyl)

Studies on direct-current electrical conductivity and optical properties of a new solution of processable conducting polymer are reported. Electrical conductivity of thin films of the polymer on glass plate at room temperature was 6×10⁻⁶ S/cm. Study of conductivity with variation of temperature does not provide any definite thermal activation energy, which is in accordance with the amorphous nature of polymer. Optical absorption data adopting the Bardeen equation showed that maximum ‘optical gap’ (E _g ) is 3.30 eV. Doping with Br₂-vapor was found to be only partially effective in decreasingE _g by 0.43 eV. The polymer was found to be quite stable under normal atmospheric conditions. Environmental stability of both undoped and doped polymer has been discussed. Part 2: [5]     

Structure relaxation after temperature jumps in homogeneous polystyrene/poly(styrene-co-bromostyrene) blends

Concentration fluctuations in polymer blends and their change after a temperature jump were studied by time-dependent small angle X-ray scattering experiments. Measurements were conducted on homogeneous mixtures of polystyrene and a partially brominated derivative. Structure factors in thermal equilibrium show the form given by the random phase approximation, thus enabling a direct determination of the-parameter and the mean radius of gyration. TheT-dependence of can be understood as the result of superposed enthalpic contributions and a free volume term. In theT-jump experiments, samples were quenched to temperatures near T_g. Relaxation occurs on the time scale of minutes and is nonexponential, becoming slower with time. Initial relaxation rates increase with increasing scattering vectorsq in accordance with theoretical predictions.     

Physicochemical properties of α, ω-type bolaform surfactant in aqueous solution. Eicosane-1,20-bis(triethylammonium bromide)

The physicochemical properties of the, - type (bolaform) surfactant, eicosane-1, 20-bis(triethylammonium bromide) (C₂₀Et₆), in aqueous solution have been investigated by means of surface tension, electrical conductivity, dye solubilization, and time-resolved fluorescence quenching (determination of average micelle aggregation number). Using electrical conductivity, the critical micelle concentration of C₂₀Et₆ was found to be 6.0×10^–3 mol dm^–3 and the ionization degree of C²⁰Et₆ micelle was found to be 0.42. From surface tension measurments, the molecular area of C₂₀Et₆ at the air-water interface was about twice that of normal type surfactants such as dodecyltrimethylammonium bromide (DTAB). The solubilizing power of micellar solution of C₂₀Et₆ toward Orange OT was 1.0×10^–2 mole of dye per mole of surfactant, i. e., slightly smaller than that of DTAB. The micelle aggregation number,N, was found to be 17±2 by time-resolved fluorescence quenching. C₂₀Et₆ showed a very small temperature dependence ofN, much less than for normal surfactants.     

K+-montmorillonite: its electric double layer extension and point of zero charge by diffusion potential

The dependence of the counterion transference number on the distance from the charged surface, that is, on the water (solution) thickness, is used for an approximation of the extension of the electric double layer (edl) in K⁺-montmorillonite.The extension of edl in K⁺-montmorillonite in 10^–2–10^–3 M KCl solutions is approximately 3.7k ^–1, wherek ^–1 is the Debye length.The dependence of the counterion transference number on the pH of water (solution) is used for estimating the point of zero charge (pzc) of K⁺-montmorillonite; the estimated pzc=1.