Search results for "Molar"

Heat capacities, volumes and solubilities of pentanol in aqueous alkyltrimethylammonium bromides

1988

Apparent molar heat capacities and volumes of pentanol, 0.05m in decyl-, tetradecyl- and hexadecyltrimethylammonium bromides micellar solutions, were measured at 25°C. They were assumed to approach the standard infinite dilution values and rationalized by means of previously reported equations following which the distribution constant between the aqueous and the micellar phase, heat capacity, and volume of pentanol in both phases are simultaneously derived. The present results show that the volume of the micellar core does not seem to have a significant effect on the apparent molar volume and heat capacity of pentanol in the micellar phase and on the free energy of transfer of pentanol from…

Cyclodextrins in polymer synthesis: photocrosslinkable films via free radical copolymerization of methylated β-cyclodextrin-complexed styrene with so…

2001

The copolymerization of a methylated-β-cyclodextrin (m-β-CD) 1:1 host-guest compound of styrene (1a) with various molar ratios of sodium 4-(acrylamido)-phenyldiazosulfonate (2) is described. The copolymerization of complex 1a with 2 was carried out in water with 2,2′-azobis(N,N′-dimethyleneisobutyramidine)-dihydrochloride as the free radical initiator at 40°C. Depending on the amount of 2 incorporated in the copolymer, water- or DMF-soluble copolymers of high molar mass were obtained. Irradiation of the copolymers with UV light in solution resulted in rapid decomposition of the azo chromophore, and irradiation of the polymers as films led to crosslinking and thus to insolubility.

1978

A reaction vessel automatically controlled by magnetic valves is described which allows kinetic measurements of reactions with half lives t1/2≥2s by gravimetric determination of the conversion. Thus, it covers the gap between the flow tube and the conventional reaction vessel. The influence of mixing time and filling time on the molecular weight distribution of an anionically prepared polymer is discussed.

Zur kinetik des einstellvorganges im osmometer. IV. Bestimmung des zahlenmittels des molekulargewichts bei unfraktionierten polymeren1

1962

Der durch teilweise Permeation bedingte Fehler des gemessenen osmotischen Druckes eines unfraktionierten Polymeren kann berechnet werden, wenn die fur das Permeationsverhalten masgebenden Konstanten der Membran und die molekulare Verteilungsfunktion des Polymeren bekannt sind. Unter diesen Voraussetzungen wird unter Verwendung fruher abgeleiteter Beziehungen1 der durch Gl. (1) definierte Fehlbetrag Δt berechnet. Ist die spezielle Verteilungsfunktion nicht bekannt, so kann der Fehlbetrag fur ein bestimmtes Polymeres abgeschatzt werden, wenn auser einer osmotischen Mesreihe eine Bestimmung des Gewichtsmittels des Molekulargewichts Mw (bzw. Pw) vorliegt. Voraussetzung der Rechnung ist die Kenn…

Size‐Exclusion Chromatography in Single and Mixed Eluents: Effects of Sorption of Solvent and Polymer Solutes on Novel TSK‐Gel Super AW Columns

2005

Abstract The novel TSK Gel Super AW column packing is based on a polymeric gel with residual hydrophobic and hydrophilic groups on the gel surface. These groups can act as active sites making the chromatographic support compatible both with polar and apolar eluents. This interesting property allows the elution of systems of very different polarities but also induces binary polymer–gel, polymer–solvent, and solvent–gel enthalpic interactions that lead to a mixture of separation mechanisms: repulsion, partition, or adsorption besides the main size‐exclusion chromatography (SEC) mechanism. For this reason, the elution behaviour of many and diverse polymer/solvent systems has been studied in th…

Thermodynamic Properties of Sodium n-Alkanecarboxylates in Water and in Water + Cyclodextrins Mixtures

1998

Densities and heat capacities of water−substrate, water−cyclodextrin, and water−substrate−cyclodextrin systems were determined at 298 K. The substrates studied are sodium n-alkanecarboxylates (CnCOONa) (from sodium acetate to sodium decanoate) and the cyclodextrins are hydroxypropyl-α-cyclodextrin (HP-α-CD), hydroxypropyl-β-cyclodextrin, (HP-β-CD), hydroxypropyl-γ-cyclodextrin (HP-γ-CD) and β-cyclodextrin (β-CD). The apparent molar volumes and heat capacities of CnCOONa in water were calculated as functions of concentration. The standard partial molar properties agree with those obtained by using the additivity rule. HP-β-CD essentially does not affect the thermodynamic properties of C1COON…

N,N,N-Alkyloctyldimethylammonium Chlorides in Water: A Thermodynamic Investigation

1993

Abstract Specific conductivities, densities, heat capacities and enthalpies of dilution at 298 K and osmotic coefficients at 310 K were measured for N,N,N -octylbutyldimethylammonium, N,N,N -octylpentyldimethylammonium, and N,N -dioctyldimethylammonium chlorides in water as functions of concentration. From the specific conductivity data, the CMC and the degree of the counterion dissociation have been calculated. It is shown that additional CH 2 groups in the variable alkyl chain affect both CMC and β less than they do in the single chain surfactants. The partial molar volumes, heat capacities, relative enthalpies, nonideal free energies, and entropies at 298 K were derived as functions of t…

Phase behavior of the system hyperbranched polyglycerol+methanol+carbon dioxide

2010

Abstract Phase equilibrium data have been measured for the ternary system hyperbranched polyglycerol + methanol + carbon dioxide at temperatures of 313–450 K and pressures up to 13.5 MPa. Phase changes were determined according to a synthetic method using the Cailletet setup. At elevated temperatures the system shows a liquid–liquid–vapor region with lower solution temperatures. Besides the vapor–liquid and liquid–liquid equilibria, the vapor–liquid to vapor–liquid–liquid and vapor–liquid–liquid to liquid–liquid phase boundaries are reported at different polymer molar masses and can serve as test sets for thermodynamic models. A distinct influence of the polymer molar mass on the vapor–liqu…

Phase separation of blends of polydisperse polymers: Comparison between experiment and theory for the system poly(dimethylsiloxane)/poly(ethylmethyls…

1996

Cloud point curves were measured turbidimetrically for blends (upper critical solution temperatures ; UCSTs) of poly(ethylmethylsiloxane) (PEMS) and four different samples of poly(dimethylsiloxane) (PDMS) ; the weight average molar masses in kg/mol are 31.2 for PEMS and 10.4, 15.5, 18.1 and 24.0 for PDMS ; all components have polydispersity indices D (= M w /M n ) within the range from 1.82 to 2.67. Corresponding calculations on the basis of the Flory-Huggins theory (three adjustable parameters) account for the polydispersity; molecular weight distributions are represented by the generalized Schulz-Flory equation. Calculated cloud point curves agree very well with those measured, if individ…

Shear Effects on the Phase Diagrams of Solutions of Highly Incompatible Polymers in a Common Solvent. 2. Experiment and Theory

1997

Cloud point temperatures (Tcp) were measured at different constant shear rates for three representatives of the ternary system cyclohexanone/polystyrene/poly(n-butyl methacrylate) (CHO/PS/PBMA) by means of a newly constructed rheo-optical apparatus that can be operated in the temperature range from 0 to 100 °C up to maximum shear rates of 1440 s-1 and maximum stresses of 384 Pa. In all cases one observes an extension of the homogeneous region as the shear rate γ is raised. With the system CHO/PS 196w/PBMA 2050 (the figures denote the molar masses of the polymers in kilograms/mole) the effects become maximum for high concentrations of PBMA, where the demixing temperatures increase by more th…