Phase separation phenomena in solutions of poly(2,6-dimethyl-1,4-phenyleneoxide) in mixtures of trichloroethylene, 1-octanol,and methanol: Relationship to membrane formation

The phase boundaries in the quaternary system consisting of the polymer poly(2,6-dimethyl-1,4-phenyleneoxide) (PPO

1 PPO is a registered trademark of the General Electric Company.

), the solvent trichloroethylene (TCE), and the nonsolvents 1-octanol (OcOH) and methanol (MeOH) are determined. The kinetics of crystallization are investigated by pulse-induced critical scattering. The formation and properties of PPO membranes are discussed in relation to the phase separation phenomena.     

The analysis of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO® resin) in mixtures of PPO resin,polystyrene, and copolymers of PPO resin and polystyrene

A method of determining the quantity of ungrafted poly(2,6-dimethyl-1,4-phenylene oxide) (PPO®

1 Trademark of General Electric Company.

resin) in mixtures of such polyphenylene oxide or PPO resin, polystyrene (PS), and graft copolymers of PPO resin and PS is described. The technique is a combination of physical and chemical separations and gel permeation chromatographic (GPC) analysis. The extent of grafting on PPO resin and the quantity of ungrafted PPO resin were calculated from molecular weight data and compositional analysis.     

Dependence of cooperative relaxation of amorphous polymers on diluent concentration

The Adam–Gibbs molecular theory, which describes the temperature dependence of relaxation phenomena in the main transition region in terms of the configurational entropy of a system, has been extended to include the effect of concentration of a low-molecular-weight compound on the viscoelastic behavior of concentrated polymer solutions. The concentration dependence of relaxation times in the polymer–diluent mixture leads to an expression of the concentration dependence both of the shift factor in the Williams–Landel–Ferry (WLF) equation and of the glass transition temperature T_g of the mixture. The constants of the WLF equation and the concentration dependence of T_g are given in terms of a difference between the specific heats of the liquid and glass ΔC_p of the equilibrium temperature T₂ of the second-order transition, and of the parameter Δμs/k, which includes the chemical potential Δμ and the configurational entropy s of the smallest cooperatively rearranging region. The resulting relationships also predict the temperature dependence of the constants of the concentration WLF equation. Good agreement was found between theory and the viscoelastic and T_g data on the systems poly(vinyl acetate) + diethyl phthalate, poly(methyl methacrylate) + diethyl phthalate and polystyrene + dibutyl phthalate. This finding indicates that the configurational entropy, at least in the first approximation, is responsible for the concentration dependence of relaxation phenomena in concentrated polymer solutions.     

Synthesis and properties of some new polyimidosulfides with highly mobile backbones

Various alkanedithiols [HSRSH; R = (CH₂)_3–6 or? CH₂CH₂OCH₂CH₂? ] add to the carbon-carbon double bonds of N,N′-bismaleimido-1,8-octane ( 1 ) at room temperature in m-cresol that contains triethylamine as a catalyst to produce the corresponding polyimidosulfides ( 3 ) in yields of 75–86% and with inherent viscosities (ηinh) of 0.30–1.05 dL/g. In general ( 3 ) are amorphous, elastomeric materials that undergo glass transitions (T_g) within the range of 6.5–13°C but product ( 3a ) [R = (CH₂)₆] is a tough, leatherlike polymer that exhibits T_g = 35°C and a melting transition at 77°C. X-ray analysis indicates that ( 3a ) is ca. 37% crystalline. In addition to further details of the synthesis and properties of polyimidosulfides ( 3 ), comparisons are made between crystalline ( 3a ) and a structurally analogous but morphologically dissimilar, elastomeric polyaspartimide synthesized earlier

1 J. E. White, M. D. Scaia, and D. A. Snider, J. Appl. Polym. Sci., in press.

from ( 1 ) and N,N′-dimethyl-1,6-hexanediamine.     

Molecular modelling of polymers, 1. Prediction of critical values of oligomethylenes

Most procedures for the estimation of critical values of oligomethylenes assume these critical values to depend only on the chain length n and/or the molecular weight M. In this work, we introduce new equations for estimating the critical values by inclusion of quantum chemical data calculated by a semiempirical SCF-MO

1 SCF-MO: Self-consistent field, molecular orbital.

method (AM1). These models give a much superior prediction for the critical values such as the normal boiling point T_b, critical temperature T_c, critical pressure P_c, critical valume V_c, surface tension y_b and enthalpy of vaporization ΔH_vp of 18 oligomethylenes. The predictions for polyethylene (with infinite chain length) for the values of T_b, T_c, P_c, V_c, ΔH_vp and y_b are 1029.3 K, 1029.3 K, 1.013 bar, 15723.3 m³/mol, 0 KJ/mol and 0 mN/m, respectively.     

Hydrolysis of 2-aminoethanethiolsulfate ions

The kinetics of the acid catalyzed hydrolysis of 2-aminoethanethiolsulfate (AETS) ions were investigated. The dependence of the hydrolysis rate constant on acidity and temperature was determined. The hydrolysis rate equation can be expressed as where H_o is the Hammett acidity function. The rate constant, k, can be expressed as The pK_a's for the compound were measured and literature value of pK_a was found to be in error. The values determined in this study are pK_a1 < ?0.5 and pK_a2 = 9.1 ± 0.1. General acid catalysis of the hydrolysis reaction was found not to proceed to a significant degree. © 1994 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Intrinsic symmetry of the AABb-type distribution

By taking an A_aB_b-type polymerisation as an example

1 Each unit has a functional groups of type A and b of type B.

, an intrinsic symmetry of the equilibrium number fraction distribution of species is revealed. The symmetry shows that the distribution is invariant under transformation between the variables which describe the total system and the variables which describe the sol. It results that, when the polymer quantities for the pre-gel regime are given, the corresponding quantities for the post-gel regime can easily be obtained. As an illustration, the k th radius of an A_aB_b-type polymerisation is discussed.     

Interfacial tension measurement with the neumann triangle method

The interfacial tensions between polystyrene (PS) and poly(butylene terephthalate)

1 System. name: poly(tetramethylene terephthalate).

(PBT), PS/poly(methyl methacrylate) (PMMA), and PBT/PMMA pairs have been obtained by employing the Neumann Triangle method (NT). The results are in good agreement with those obtained by the breaking thread method. For the first time, the NT method was applied to a reactive polymer pair with an in-situ compatibilizer to measure the interfacial tension. We found that the interfacial tension of the PS/PBT system with a small amount of poly(styrene-co-glycidyl methacrylate)

2 System. name of glycidyl: 2,3-epoxypropyl.

(PS-GMA) is significantly reduced compared to that without PS-GMA.     

The He(Iα) Photoelectron Spectra of the Perfluoroderivatives of Trisannelated Benzenes and Tetrakisannelated Cyclooctatetraenes

The He(Iα) photoelectron (PE) spectra of tris(perfluorocyclobuta)benzene 4 (F)

1 3,3,4,4,7,7,8,8,11,11,12,12-Dodecafluorotetracyclo[8.2.0.0^2,5.0^6,9]dodeca-1,5,9-triene

, tris(perfluorocyclopenta)benzene 5 (F)

2 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-Octadecafluoro-2,3,4,5,6,7,8,9-octahydro-1H-trindene.

, tetrakis(perfluorocyclobuta)cyclooctatetraene 6 (F)

3 3,3,4,4,7,7,8,8,11,1l,l2,l2,l5,15,16,16-Hexadecafluoropentacyclo[12.2.0.0^2,5.0^6,9.0^10,13]hexadeca-1,5,9,13-tetraene.

, and of tetrakis(perfluorocyclopenta)cyclooctatetraene 7 (F)

4 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-Tetracosafluoro-1,2,3,4,5,6,7,8,9,10,11,12-dodeca-hydrotetracyclopenta[a,c,e,g]cyclooctene.

are reported. A tentative assignment of the PE spectra is derived by empirical correlation with those of relevant reference compounds. The results suggest that 6 (F) retains the D_4h-conformation in the gas phase, i.e. A conformation with a planar cyclooctatetraene ring, as observed in the crystal. All four compounds exhibit a sharp increase of their first ionization energies, relative to the corresponding parent hydrocarbons, due to the perfluoro effect.     

Stereochemistry of the Platinum Catalyzed Hydroformylation of Olefins

The deuterioformylation of (Z)- or (E)-2-butene catalyzed by [DIOP]Pt(SnCl₃)-Cl

1 DIOP=2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane.

gives predominantly erythro- or threo-1,3-[²H]₂-2-methylbutanal respectively. Hence, hydroformylation by this catalytic system must take place with cis-stereochemistry.     

Glow discharge polymerization of tetramethylgermanium

A glow discharge polymerization technique was applied in the preparation of germanium-containing polymers. The colorless and transparent polymer films formed from tetramethylgermanium (TMG) were investigated by elemental analysis, infrared (IR) spectroscopy, and ESCA. The reaction of TMG was accompanied by the rupture of bonds between Ge and CH₃ groups which led to mixtures of polymers that consisted of CH₃, CH₂, Ge? CH₃, Ge? O? C, and Ge? O? Ge groups and germanium metal. Most Ge species present at the outermost layers of the films were oxidized subsequently by air, whereas the Ge species at the inner layers still existed as Ge metal. This film-forming process can be explained by the concept of atomic polymerization proposed by Yasuda.

1 See H. Yasuda, J. Polym. Sci. Macromol. Rev., 16 , 199 (1981).

     

Comment on the Estimation of the Dimerisation Constant of Caffeine

Reasons for the low reliability of the

1 Compare e.g. former results cited in [3][4] with our results in [3].

H-NMR estimation of the dimerisation constant of caffeine in D₂O are discussed. The main reasons are (1) strong influence of small variations in the monomer shifts δ₀ which are to be determined by extrapolation, and (2) disturbance by the formation of higher oligomers. The dilemma ist that attempts to minimize errors from (1) increase the influence of (2) and vice versa.     

The Distribution of Glass Transition Temperatures in Ultrathin Polymer Films Controlled by Segment Density or Interfacial Interaction

Nowadays, the microscopic mechanism controlling the distribution of local glass transition temperatures (T_gs) across thin polymer films is still unclear and thus large‐scale applications of polymer films are restricted. Dynamic Monte Carlo simulations are performed to investigate the key factors dominating the distribution of layer T_gs in two kinds of capped ultrathin films with and without attractive polymer–substrate interactions, respectively. For the film without polymer–substrate interaction, the interfacial layer T_g is lower than the middle layer T_g. Additionally, the layer T_gs and the layer segment densities below T_g are linearly correlated, indicating that polymer density determines the distribution of layer T_gs. However, for the films with polymer–substrate interactions, the interfacial layer T_g increases dramatically with the raise of interfacial interactions, while the middle layer T_g decreases slightly. The interfacial layer T_g is proportional to the strength of interfacial interaction, while the middle layer T_g is linearly correlated with the segment density of the middle layer below T_g. Namely, interfacial interaction is the main factor dominating the interfacial layer T_g, while segment density controls the middle layer T_g.

     

Characterization of solute-membrane interactions by TMA-measurements

On the basis of relationships derived by Oplatka et al. [1] correlating the derivative of tensile stress with respect to temperature for a polymer strip at constant length, (/T) _t , with the derivative of entropy with respect to strip length, (S/l)_T, relationships are derived relating the derivation of strip length with respect to temperature under constant tensile stress, (l/T), with the derivative of entropy with respect to tensile load, (S/) _T . The developed relationships are applied to evaluate TMA (thermomechanical analysis) measurements performed with asymmetric and homogeneous cellulose acetate membranes where the membrane strips were kept in deionized water. Moreover, TMA measurements were performed with homogeneous CA membranes while maintaining the membrane strips in bathing solutions of different, but in each instance, constant electrolyte concentrationc _s (e.g., LiCl, LiNO₃, Li₂SO₄, CaCl₂; 0 c _s saturation). Under constant tensile stress, , as-cast asymmetric CA membranes, which are kept in deionized water, first elongate with increasing temperature at temperatures up to about 50°C. However, they shrink with a further increase of temperature in the temperature range 50°C up to about 90°C, whereas creeping starts at temperatures beyond 90°C, leading again to an elongation of the strip with a further increase of temperature. The negative apparent coefficient of thermal expansion, existing between 50° to 90°C, is consistent with shrinking phenomena observed with asymmetric CA membranes [2]. In addition, it correlates well with both an entropy decrease with increasing tensile stress at constant strip length and an entropy increase with decreasing strip length at constant tensile stress. Contraction of the strip with increasing temperature at constant tensile load might be due to increasing coil formation of polymer molecules rendered possible by disintegration of joints such as H-bonds between polymer chains. Depending on the electrolyte of the bathing solution and its concentration, homogeneous CA membranes exhibit positive and negative apparent linear coefficients of thermal expansion under constant tensile stress.     

Chemie von α-Aminonitrilen. 12. Mitteilung. Sondierungen über thermische Umwandlungen von α-Aminonitrilen

Chemistry of α-Amino Nitriles

1 11. Mitteilung: [1].

. Exploratory Experiments on Thermal Reactions of α-Amino Nitriles The paper extends a previously published report [4] on chemical properties of α-amino nitriles and of members of the C₃H₄N₂ ensemble (Scheme 1) as observed in experiments carried out under non-aqueous conditions. The reactions investigated and the observations made are summarized in some detail in the English footnotes (*) referring to Schemes 1–17 and Fig. 1.     

Struik law for enthalpy retardation at the glass transition in poly(n-alkylmethacrylates) measured by DSC aging experiments

Results of calorimetric (DSC) experiments on a series of poly (n-alkylmethcrylates), from methyl to pentyl, after different aging timest _e at different aging temperaturesT _e are presented. The aging behavior is quite different from that in other polymers, for example PS. For all poly(n-alkylmethacrylates) investigated the aging peak temperatureT _max is shifted parallel to the aging temperatureT _e in a large temperature interval below the glass temperature. The results are discussed with respect to shear and entropy response in the splitting region.     

Structure et synthèse de la damascénone (triméthyl-2,6,6-trans-crotonoyl-1-cyclohexadiène-1,3), constituant odorant de l'essence de rose bulgare (rosa damascena Mill.

Damascenone

1 DORICENONE (trade mark applied for by Firmenich & Cie, Geneva).

an odoriferous ketone isolated in minute amounts from Bulgarian rose oil (Rosa damascena Mill.) is shown to be trans-2,6,6-trimethyl-1-crotonoyl-cyclohexa-1, 3-diene (I). A synthesis starting from beta;-cyclocitral is described for this conspicuous constituent of rose oil, which displays a powerful fragrance. The synthesis of four related, more saturated ketones, damascones

2 DORINONE (trade mark applied for by Firmenich & Cie, Geneva).

, is also described.     

Synthesis of soluble all-trans oligomers of 2,5-diheptyloxy-p-phenylenevinylene via olefin metathesis

In this paper we report on the synthesis of all-trans oligomers of 2,5-diheptyloxy-p-phenylenevinylene (2,5-diheptyloxy-PV) via olefin metathesis condensation of 2,5-diheptyloxy-1,4-divinylbenzene

1 The correct IUPAC name is 1,4-bis(heptyloxy)-2,5-divinylbenzene. The name 2,5-diheptyloxy-1,4-divinylbenzene is used in order to underline the structural similarity to 2,5-diheptyloxy-p-phenylenevinylene oligomers.

(2,5-diheptyloxy-DVB). The preparation of the monomer is also described. The Schrock type molybdenum alkylidene complex Mo(NPhMe₂)(CHCMe₂Ph)(OCMe[CF₃]₂)₂ was used as metathesis catalyst. The oligomer product obtained was characterized by means of ¹H NMR, IR and UV/Vis spectroscopy and gel permeation chromatography.     

Ethylene-Octene Copolymer-Nanosilica Nanocomposites: Effects of Epoxy Resin Functionalized Nanosilica on Morphology,Mechanical, Dynamic Mechanical and Thermal Properties

A comparative study of the structural, thermal, mechanical and thermomechanical properties of ethylene-octene copolymer 1

1 Ethylene-octene copolymer is produced using Dow's INSITETM ™ constrained geometry catalyst and process technology. ENGAGE the trade name of this copolymer.

(mPE) 2

2 This copolymer will be represented as mPE .

nanocomposites synthesized with pure nanosilica (NS) and nanosilica-functionalized with diglycidyl ether of bisphenol-A (ENS) has been reported. These nanocomposites were prepared using “melt mixing” method at a constant loading level of 2.5 wt. %. The effects of pure nanosilica (NS) and epoxy resin-functionalized-nanosilica (ENS) on the above mentioned properties of ethylene-octene copolymer were analyzed by wide-angle-x-ray diffractometer (WAXD), transmission electron microscope (TEM), thermo gravimetric analyzer (TGA), differential scanning calorimeter (DSC), dynamic mechanical analyzer (DMA) and scanning electron microscope (SEM). TEM studies have shown a better dispersion of nanoparticles in case of ethylene-octene copolymer-epoxy resin-functionalized-nanosilica nanocomposite (mPE-ENS) than that of ethylene-octene copolymer-nanosilica nanocomposite (mPE-NS). The tensile tests show that organic modification of nanosilica particles brings up an appreciable increase in yield strength, ultimate tensile strength and elongation at break of the polymer. DMA studies have shown an increase in the storage modulus and glass transition temperature for mPE-ENS with respect to mPE-NS. Further, the TGA results have shown a higher thermal stability for mPE-ENS in comparison to mPE-NS.