Search results for "MOLA"

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…

Effect of core-forming molecules on molecular weight distribution and degree of branching in the synthesis of hyperbranched polymers

1998

The polydispersity index, the molecular weight distribution (MWD), and the degree of branching ( ) are calculated for hyperbranched polymers obtained in self-condensing vinyl polymerization of AB* monomers in the presence of a core-forming molecule (i.e. a multifunctional initiator, Bf*). Two cases are considered:  (a) batch polymerization, i.e., with all components mixed together; (b) semibatch polymerization, i.e., slow addition of the monomer to the core-forming molecule. The results obtained for the latter case are also valid for polycondensation of AB2 monomers. The presence of core-forming molecules leads to a considerable narrowing of the MWD's, the polydispersity index decreasing wi…

Ring opening polymerization of $\varepsilon$-caprolactone in the presence of wet $\beta$-cyclodextrin: Effect of the operative pressure and of water …

2016

International audience; The ring opening polymerization (ROP) of $\varepsilon$-caprolactone (CL) in the presence of $\beta$-cyclodextrin ($\beta$-CD) wasperformed in batch reactors both at room pressure and with the reaction system pressurized with CO$_2$, N$_2$ orAr. Significant enhancements of the polymerization rate was observed when the ROP was carried out withwet $\beta$-CD under pressure. For example, after 24 hours at 120° C with a $\beta$-CD/CL molar ratio of about1/100, the monomer conversion increased from 4 to 98–99% when the pressure was changed from 0.1to 12.5–13.0 MPa independent of the nature of the compressing gas. MALDI-TOF analyses indicated thata major fraction of polymer…

Volume and heat capacity studies to evidence interactions between cyclodextrins and nicotinic acid in water

2008

Density and heat capacity of the water+cyclodextrin (CD), water+nicotinic acid (NA) and water+CD+NA mixtures were determined at 298.15 K. CDs with different cavity size and alkylation were selected. From the experimental data the apparent molar properties were calculated. Assuming the formation of inclusion complexes of 1:1 stoichiometry, these properties were modeled and provided the stability constants of CD/NA inclusion complexes and the corresponding property change. The binding of NA with the smallest sized alpha-cyclodextrin (alpha-CD) generates more stable complexes accompanied by the lower volume and the heat capacity changes. These results are in agreement with earlier proposed bin…

Sequence-specific and DNA structure-dependent interactions of Escherichia coli MutS and human p53 with DNA

2013

Many proteins involved in DNA repair systems interact with DNA that has structure altered from the typical B-form helix. Using magnetic beads to immobilize DNAs containing various types of structures, we evaluated the in vitro binding activities of two well-characterized DNA repair proteins, Escherichia coli MutS and human p53. E. coli MutS bound to double-stranded DNAs, with higher affinity for a G/T mismatch compared to a G/A mismatch and highest affinity for larger non-B-DNA structures. E. coli MutS bound best to DNA between pH 6 and 9. Experiments discriminated between modes of p53-DNA binding, and increasing ionic strength reduced p53 binding to nonspecific double-stranded DNA, but had…

1990

The determination of average molecular weights and the characterization of molecular weight distributions by the ratio of the weight- to number-average molecular weights Mw/Mn from sedimentation equilibrium in the ultracentrifuge are described. The essential measurement of the density profile of the mixed solvent is conducted according to Munk (Macromolecules15, 500 (1982)). Special evaluation of the polymer band in the equilibrium allowed to deduce from the observed concentration profile Mw and Mn of a series of poly(methyl methacrylate) samples and thus to characterize the molecular weight distribution of the samples.