Ferdane Yilmaz

Comparison of the intrinsic viscosity and inverse gas chromatography techniques in determination of the exchange enthalpy and entropy parameters

Abstract The χ 1 -interaction parameters of poly(dimethyl siloxane) with methyl ethyl ketone at very low polymer concentration were determined by means of intrinsic viscosity (IV) measurements at several temperatures. The χ t ∞ -total interaction parameters of the same system at infinitely high polymer concentration were also determined using inverse gas chromatography (i.g.c.) technique around the same temperature range. Then, exchange enthalpy, X 12 , and entropy, Q 12 , parameters in the Florys equation of state theory were determined from the obtained interaction parameters. Both X 12 and Q 12 parameters obtained by IV are lower than those found by i.g.c..

Determination of exchange enthalpy and entropy parameters of poly(dimethyl siloxane) with some n‐alkanes by inverse gas chromatography

The total interaction parameter at infinitely high polymer concentration, χ t ∞, and the effective exchange energy parameter, X 12 , of poly(dimethyl siloxane) with n-pentane, n-hexane, n-heptane and n-nonane were determined around room temperature using the inverse gas chromatography technique. The values of χ t ∞ are in agreement with corresponding literature values. The exchange enthalpy X 12 and entropy, Q 12 , parameters were determined at the same temperature. The X 12 parameters increase with the carbon number of the n-alkanes, while their temperature dependence is almost negligible. The Q 12 parameters are approximately independent of temperature and carbon number of the n-alkanes.

Determination of the exchange enthalpy and entropy parameters of the equation-of-state theory for poly(dimethyl siloxane) in various solvents

Abstract The interaction parameter χt∝ and the effective exchange energy parameter X 12 at infinite dilution of cyclohexane, benzene and chlorobenzene with poly(dimethyl siloxane) were determined around room temperature, according to relations given in the Flory formulation of the equation-of-state theory using the inverse gas chromatography technique. Then, the exchange enthalpy X12 and entropy Q12 parameters were determined by using a relation for the enthalpy interaction parameter χh of the equation-of-state theory, which is arranged for the inverse gas chromatography conditions. The values of the above-mentioned parameters are comparable with the values obtained earlier with other methods. The X12 and Q12 parameters of cyclohexane increase slightly with temperature, while those of benzene and chlorobenzene are almost independent of temperature.

Determination of exchange enthalpy and entropy parameters of the equation-of-state theory for poly(dimethyl siloxane) and some aromatic solvents by inverse gas chromatography

The specific retention volumes, V g o of toluene, ethyl benzene, n-propyl benzene and isopropyl benzene on poly(dimethyl siloxane)(PDMS) were measured at temperatures between 333 and 403K by inverse gas chromatography. The parameters of hard-core interaction, X t ∞, effective exchange energy, X 12 , exchange enthalpy, X 12 , and exchange entropy, Q 12 in the equation-of-state theory were determined. The parameters X t ∞ of the isopropyl benzene-PDMS pair decreased from 0.65 to 0.60 while those of others decreased from around 0.77 to 0.69 with increasing temperature. The values of the parameters X 12 also decreased as molecular weight of the substituted aliphatic group on the benzene ring of the solvent increased, ie 15J cm -3 in toluene and 5J cm -3 in isopropyl benzene. Both X 12 and Q 12 show negligible dependence on temperature.

Thermodynamic interactions and characterization of poly(p-chlorostyrene) with some aliphatic and aromatic probes by inverse gas chromatography

Abstract Some thermodynamic quantities were obtained for the interactions of poly( p -chlorostyrene) with n-pentane, n-hexane, n-heptane, benzene, toluene, isopropylbenzene and n-propylbenzene by the inverse gas chromatography method in the temperature range 150–170°C. The specific retention volumes ( V 0 g ), weight fraction activity coefficients of solute probes at infinite dilution ( Ω ∞ 1 ), Flory-Huggins thermodynamic interaction parameters ( χ ∞ 12 ), interaction parameters based on hard-core volumes ( χ∗ 12 ), effective exchange interaction parameters ( X 12 ) of the equation of state theory, between polymer and solutes are given. The molar enthalpy of sorption ( Δ H s ), the partial molar heat of mixing at infinite dilution ( Δ H ∞ 1 ) and the solubility parameter of polymer ( γ 2 ) were also calculated.

A study on the parameters of exchange enthalpy, X12, and entropy, Q12, in the equation-of-state theory for some polymer-solvent pairs

Abstract The parameters of exchange enthalpy, X 12 , and entropy, Q 12 have been determined for cyclopentane, tetrahydrofurane and 1,4-dioxane with poly(dimethyl siloxane) around room temperature using inverse gas chromatography technique. The parameters X 12 were compared to the parameters calculated by means of the Berthelot relationship from characteristic pressures of the pure components in the mixtures. The parameters Q 12 were compared to differences of thermal pressure coefficients of the pure components in the mixtures.

Determination of equation of state parameters of poly(dimethylsiloxane)-benzene system by intrinsic viscosity

Abstract The equation of state exchange energy ( X 12 ) and entropy ( Q 12 ) parameters and the ratio of contact sites ( S 2 / S 1 ) of the poly(dimethylsiloxane)-benzene system were determined using equation of state theory and intrinsic viscosity measurements. The values of X 12 and Q 12 parameters for S 2 / S 1 =0.67 are found to be 16.64 J cm −3 and −0.0394 J cm −3 K −1 , respectively.

Application of thermal blob theory to intrinsic viscosity measurements of poly(4‐chlorostyrene) above the theta point

Macromolecular chains obey purely Gaussian statistics close to the theta temperature. An asymptotic regime is also reached far above the theta point. Thermal blob theory permits an approximate calculation of thermal expansion factor. In this theory, an adjustable parameter is used as a prefactor (A * N 1 ) in order to calculate the reduced blob parameter (N/N c ). In this work, we proposed a different approach to evaluate (A * N 1 ) by plotting TM w 1/2 /α η 5 against τM w 1/2 . Chain expansion data of poly(4-chlorostyrene) in various solvents is used to evaluate viscosity expansion factors at various temperatures. It seems that predictions of thermal blob theory provide a better fit to experimental points rather than those evaluations based on Flory-type approaches.