Research Team

Prof. Dr. Uğur YAHŞİ

Assoc. Prof. Dr. Cumali TAV

Abdulkarem NEWATI (BILYAZ Information & Innovation Ltd.), M.Sc. student with thesis title: "Statistical Thermodynamics of Macromolecular System in terms of Simha-Somcynsky Theory in conjunction with Lattice Cluster Theory"

Murat Yavuz YENER (Ph.D. student)

Graduated Students

Ph.D.

Fatma Şahin (2013),  “Analyzing Newtonian and Non-Newtonian Vıscous Behavior of Polymers in Terms of Free Volume Using Simha-Somcynsky Hole Theory"

Saygın KÜZECİ (2011), “Yavaş Pozitron Demet Sistemi Kullanılarak Polimerlerin Yüzey Serbest Hacim İlişkisinin Derinlikle İlişkilendirilmesi”

Mustafa Aslan (2009), “Dallanmış ve Dendrimer Makromoleküler Yapıların İstatistiki Termodinamiği”

Master of Science

Gülsüm Akdeniz (2006), “Linking Free Volumes in Viscous Behavior of Polymer Liquids”

Cihat Boyraz (2004), “Linking the Bulk Properties of Surface Tension of Chain Molecular Liquids”

Fatma Şahin (2002), “Linking the Equilibrium and Transport Theories of Viscous Behavior of Some Hydrocarbon Mixtures”

Ahmet Sayıcı (2002), “Hidrokarbon Sıvıların İstatistiki Thermodinamiği: Utrasonik Ses Hızının Termodinamik Nicelikler İle İlişkilendirilmesi”

Semih Aydın (2002), “Hidrokarbon Sıvıların İstatistiki Termodinamiği: İzotermal ve İzentropik Sıkıştırılabilirliğin Serbest Hacim Metodu ile İncelenmesi”

Saygın Küzeci (1999), “Statistical Thermodynamics of Hydrocarbon Molecular liquids: Investigation of Physical and Chemical Mixtures using Characteristic Group Contributions"

Ebubekir Usanmaz (1999), “Interrelationship between PVT and Viscous Behavior of Polymer Liquids”

 

Colloborators

Tomas SEDLACEK, Centre of Polymer Systems, Tomas Bata University in Zlin, Czech Republic

Andrea SORRENTINO, Institute for Polymers, Composites and BiomaterialsNational Research CouncilPorticiItaly

Yrd. Doç. Dr. Kemal ULUTAŞ (İstanbul Üniversitesi Fizik Bölümü) 

Prof. Dr. Deniz DEĞER (İstanbul Üniversitesi Fizik Bölümü)

 

Research Topics

Statistical Thermodynamics of Polymers

Uğur Yahşi

The thermodynamics of fluids with dense chain molecules is an important subject both from the point of their physical specifications and a generalization of statistical thermodynamics of simple fluids. In our treatise the cell model of Lennard-Jones and Devonshire [1], generalized to assemblies of chain molecules due to Prigogine et al. [2,3], is employed. Simha and Somcynsky (SS) [4] made an arrangement in the model increasing the disorder by utilizing vacancies or holes in the underlying quasi-lattice. An established equation of state was intensively applied to low and high molar mass fluids [5], with significant quantitative achievement. It was extended to the compatible mixtures [6]. In this manner, characteristic scaling parameters have been obtained for a large number of polymers [7,8].

[1] J. E. Lennard-Jones and A. F. Devonshire, Proc. R. London, Series A, 163:53 (1937); 165:1 (1938).

[2] I. Prigogine, N. Trappeniers, V. Mathot, “The Molecular Theory Of Solutions”, North Holland Publishing Company, Amsterdam, (1957); I. Prigogine, N. Trappeniers and V. Mathot, Discuss. Faraday Soc., 15 (1953) 93.

[3] I. Prigogine, A. Bellemans and V. Mathot, “The Molecular Theory of Solutions”, North-Holland Pub. Co., Amsterdam, (1957).

[4] R. Simha and T. Somcynsky, “Macromolecules”, 2 (1969) 342.

[5] R.K. Jain and R. Simha, Macromolecules, 13(6)(1980) 1501-1508

[6] R. K. Jain and R. Simha, Macromolecules 13:1501 (1980).

[7] P. Zoller, in Polymer Handbook, J. Brandrup and E. H. Immergut, eds. (Willey, Interscience, New York, 1990).

[8] P. A. Rodgers, J. Appl. Polym. Sci. 48:1061 (1993).

Published Papers and Presentations

 “Molecular-weight Dependence of Free Volume in Polystyrene Studied by Positron Annihilation Measurements,” Z. Yu, U. Yahsi, J. D. McGervey, A. M. Jamieson, and R. Simha, J. Polymer Science B: Polymer Physics, 32, 2637-2644 (1994) (Citation Index = 81).

 “Molecular-weight Dependence of Free Volume in Polystyrene Studied by Positron Annihilation Measurements,”  Z. Yu, U. Yahsi, J. D. McGervey, A. M. Jamieson, and R. Simha, American Physical Society 1994 March Meeting,Pittsburg, Pennsylvania,  and (poster) 1994 Akron Macro Symposia, Akron, Ohio

“Equation of State of Poly(dimethylsiloxane) Melts,” V. K. Sachdev, U. Yahsi, and R. K. Jain, J. Polymer Science B: Polymer Physics, 36(5), 841-850 (1998) (Citation Index = 8).

Newtonian and Non-Newtonian Viscous Behavior of Polymers in Terms of Free Volume Using Simha-Somcynsky Hole Theory

Fatma Şahin-Dinç, Tomas Sedlacek, Andrea Sorrentino, C. Tav and U. Yahşi

The Newtonian and non-Newtonian viscosities of polymer melts are very important for technical processing like molding, painting and packing; for many engineering applications like food, material and construction. In this regard, the compliance of shear rate dependent multi-parameter viscosity models with experimental results has been investigated. The most notable of these models is the Cross Model, yet being inadequate for many cases it requires several modifications. This, motivated us to establish a new model and then the model is correlated with structural hole defect.

By using the fractional series expansion of shear rate in the Eyring viscosity definition, we established a model that is a function of zero shear viscosity, h0, and critical stress parameter, t. Our proposed model requires only a single q in the fractional series expansion, includes power terms up to 2q, and approximates to the Cross model when the last power term 2q is neglected. In both cases we fitted the model to the experimental rheological data at a wide range of T-P values and we computed the parameter q and T-P functional quantities h0 and t. In all h data across a wide range of T-P values, we obtained less than % 7.14 mean deviations at ambient pressure and % 4.40 at high pressures. Thus our model provides 2-3 folds less deviation than the Cross Model at high pressures and may have significant contributions to the industrial applications of non-Newtonian viscosity.

In addition to that, by using the experimental PVT data we calculated the characteristic parameters of SS Hole Theory and hole fraction, h(T,P), as a measure of free volume. Also in regard to the relationship among PVTh values we obtained various Tait like equations among PVTh, compatible with the experimental data.

Recently, the correlation of h0 and hfs at a constant stress with h(T,P) is a focus of interest. We presented the linear dependency of our derived quantities h0, hfs and  with h and T dependent thermo-visco-occupancy function (Yh). We also showed that average mean percentage deviations of these quantities are 1.82 (significantly lower than the Cross model provides which is 2.22), 1.99 and 5.32 respectively. Furthermore, we found that the derivative of the logarithms of viscosities with respect to h (viscoholibility) decreases exponentially with h increases.

Published Papers and Presentations

“On the Non-Newtonian Viscous Behavior of Polymer Melts in Terms of Temperature and Pressure-Dependent Hole Fracation”, F. S. Dinc, T. Sedlacek, C. Tav, U. Yahsi, J Applied Polymer Sci., 131 (15), 40540 (2014) (DOI: 10.1002/app.40540)

“The Effect of Hole Fraction on Viscosity in Atactic and Syndiotactic Polystyrenes”, F. Sahin-Dinc, A. Sorrentino, C. Tav, U. Yahsi, Int. J. Thermophys, 36 (9), 3239-3254 (2015). (DOI: 10.1007/s10765-015-1990-4)

“A Non-Newtonian Viscosity Model Associated with Temperature and Pressure Dependent Hole Fraction,” F. Dinç, U. Yahşi, C. Tav ve T. Sedlacek, Turkish Physical Society 30. International Physics Congress, 2-5 September 2013, Istanbul University, Vezneciler, İstanbul, Türkiye.

Completed Thesis

Fatma Şahin (2013),  “Analyzing Newtonian and Non-Newtonian Vıscous Behavior of Polymers in Terms of Free Volume Using Simha-Somcynsky Hole Theory," PhD in Physics, Marmara University, Institute of Graduate Studies in Pure and Applied Sciences, İstanbul.

 Zero-shear Viscous Behavior of Polymers in terms of  Hole Fraction as a measure of Freevolume

Fatma Şahin,  Gülsüm Akdeniz, Ebubekir Usanmaz, U. Yahşi, C. Tav

Study of Statistical Thermodynamics of the physical structure of chain molecules and of their relations to other thermodynamic quantities is of the great essence. Especially, relating the transport properties to thermodynamic quantities has a great importance. Hence, the study of viscosity as a function of hole fraction, a measure of free volume quantity, has a great popularity. With a recently purposed new model, the link has been established between the Simha Somcynsky (SS), the equilibrium theory of statistical thermodynamic theory of liquids, and Eyring Significant Structure (ESS) transport theory. The both quasi-lattice theories assume randomly distributed highly mobile vacancies in the liquid structure. The lattice-hole SS model has been found quantitatively successful in the description of the low and high weight molecular systems.

By the model it has been perfectly established a viscous vacancy relation for normal and three-branched paraffins. Now the model is extended to the three-branch hydrocarbons with different ring attachments and their mixtures. In this study to find the PVT characteristic parameters in the SS theory, superimposing experimental PVT surface on the theoretical surface is employed. By this method we observed %0.75 maximum deviation in volume. The comparison of the deviation of viscosity calculated from the model with that of the experimental data is quite hopeful and promising. The mean deviation from linearity of the model was found %0.6 or less for each species. Moreover, the transmission coefficient and activation constant for each species were calculated and compared with their structures.

Published Papers and Presentations

“Interrelationships Between P-V-T and Flow Behavior of Hydrocarbons,” Ugur Yahsi, Polymer Engineering and Science, 38, 464-470 (1998).

“Viscous Behavior of Linear and Three-Branch Alkanes: Linking the Equilibrium and Transport Theories,” Ugur Yahsi, J. Polymer Science B: Polymer Physics, 37(9), 879-887 (1999).

“Linking the Viscous and Vacancy Behavior of High Molecular Weight Hydrocarbons,” Ugur Yahsi and Fatma Sahin, Reology Acta, 43(2),189 (2004).

“Linking the Viscous and Vacancy Behavior of Mixtures of High-Molecular-Weight Hydrocarbons,” F. Sahin, C. Tav and U. Yahsi, Int. J. of Thermophysics, 27 (5), 1501 (2006).

“Viscous Behavior of PS, PP and ABS in terms of Temperature and Pressure Dependent Hole Fraction”, G. Akdeniz, U. Yahsi and C. Tav, J. Appl. Polym. Sci., 117, 110-113 (2010).     

“Interrelationships Between P-V-T and Flow Behavior of Hydrocarbons,” L. A. Utracki, R. Simha, and U. Yahsi, XII. International Congress on Rheology, 18-23 August 1996, Quebec, QC, Canada.

“Interrelationships Between Transport and Equilibrium Theories in Statistical Thermodynamics of Liquids,” U. Yahsi, Trakya Workshop on Liquid State Physics, 31 August-4 September 1999, Trakya University, Karaağaç, Edirne.

“Viscous-Vacancy Behavior of Some Polymers: Polystyrene, Polypropylene, and Polyacrylonitrile-butadiene-styrene,” G. Akdeniz and U. Yahşi, 6. International Conference of the Balkan Physical Union, 22-26 August 2006, İstanbul University, Beyazıt, İstanbul.

“Viscous Behavior of Hydrocarbons: Linking the Equilibrium and Transport Theories,” U. Yahsi, İTÜ Statistical Physics Days, 16-17 July 1998, İstanbul Technical University, Maçka, İstanbul

“Viscous-Vacancy Behavior of High Molecular Weight Hydrocarbons: Linking the Equilibrium and Transport Theories,” U. Yahsi and E. Usanmaz, 3. National Liquid State Symposium, 28-30 May 2002, İstanbul University, Baltalimanı, İstanbul.

“The Link of the Equilibrium and Transport Theories of High Molecular Weight Hydrocarbons,” F. Şahin and U. Yahsi, 6. National Liquid State Symposium, 14-16 June 2002, İstanbul University, Baltalimanı, İstanbul.

Completed Thesis

Gülsüm Akdeniz (2006), “Linking Free Volumes in Viscous Behavior of Polymer Liquids,”  Marmara University, Institute of Graduate Studies in Pure and Applied Sciences, İstanbul.

Fatma Şahin (2002), “Linking the Equilibrium and Transport Theories of Viscous Behavior of Some Hydrocarbon Mixtures,” MSc in Physics, Marmara University, Institute of Graduate Studies in Pure and Applied Sciences, İstanbul.

Ebubekir Usanmaz (1999),  “Interrelationship between PVT and Viscous Behavior of Polymer Liquids,” MSc in Physics, Marmara University, Institute of Graduate Studies in Pure and Applied Sciences, İstanbul.

Interrelationship Between Ionic Conductivity and Vacancy in Polymer Electrolytes

Uğur Yahşi, Kemal Ulutaş, Deniz Değer and Cumali Tav

A theoretical model to interpret the conductivity of ions through polymer electrolytes is established in terms of the temperature and pressure-dependent hole fraction computed from Simha-Somcynsky hole theory. The model successfully linearizes the logarithm of PPG and PEG conductivity data with NaCF3SO3 in a 20:1 ratio for a broad range of temperature and pressure. The conductivity parameter and transmission coefficient with an additive hole fraction constant are discussed and compared for both species. The derivative of the logarithm of conductivity with respect to the hole fraction decreases inversely with the hole fraction and saturates at about 0.08 and 0.12 hole fractions for PPG and PEG, respectively.

Published Papers and Presentations

“Interrelationship Between Ionic Conductivity and Vacancy in Polymer Electrolytes,” U. Yahsi, K. Ulutas, C. Tav, D. Deger,  J. Polymer Science B: Polymer Physics, 46(9), 2249-2254 (2008).

“The Correlation Between Conductivity and Free Volume In Polymer Electrolytes Probing Positron Annihilation Lifetime Spectroscopy,” G. Erdemci, B. Çoşkun, S. Yılmaztürk, M. Yılmazoglu, H. Deligöz, C. Tav, U. Yahsi and K. Ulutas, Turkish Physical Society, 26. International Physics Congress, 24-27 September 2009, Bodrum, Turkey.

“A study on the investigation of a relationship between Free Volume and Ionic Conductivity of Polymer-Salt Electrolytes,” S. Yılmaztürk, M. Yılmazoğlu, G. Erdemci, B. Çoşkun, H. Deligöz, C. Tav, K. Ulutaş, U. Yahşi, 8th International Conference on Advanced Polymers via Macromolecular Engineering (APME), Dresden, German, Oct. 4 to 7, 2009.

“Interrelationship Between Ionic Conductivity and Vacancy of Polymer Electrolytes,” K. Ulutas, U. Yahsi, C. Tav and D. Deger, 13. Statistical Physics Days,  06-08 July 2006, Bosphorous University, Bebek, İstanbul

Interrelationship of Free Volume with Dielectric Relaxation of Polymers

Uğur Yahşi, Bilgehan Çoşkun and Cumali Tav

We present a model explaining relaxation time of PPG (Polypropylene glycol) and PPGM (Polypropylene glycol dimethylether) with different molecular weights, PPG2 (Mw = 2  kg mol-1), PPG3 (Mw=3 kg mol-1), PPGM1 (Mw=1 kg mol-1), and PPGM2 (Mw=2 kg mol-1), as a function of hole fraction at various temperatures and high pressures. Proposed model based on the structural relaxation behavior of chain molecules given by “thermo-occupancy” function in terms of temperature and temperature-pressure dependent hole fraction is discussed and compared with the free volume model. The former is the most universal behavior than the latter in terms of temperature and pressure. We discuss activation energy parameter and transmission coefficient for the species in terms of chain length and end groups such as dimethylether. Scaling relaxation time parameter in the proposed model has similar trend with relaxation time parameter of Adam-Gibbs theory.

Published Papers and Presentations

“Relaxation time of polypropylene glycol and polypropylene glycol dimethylether-like polymers in terms of fluid-phase temperature and pressure dependent hole fraction,” U. Yahsi, B. Coskun, A. Yumak, K. Boubakir, C. Tav, European Polymer Journal, 68, 226-232 (2015). (DOI:10.1016/j.eurpolymj.2015.04.038)

“On The Relaxation Time of Polymers In Terms of Temperature and Pressure Dependent Hole Fraction,” B. Çoşkun,U. Yahşi and C. Tav, Turkish Physical Society, 26. International Physics Congress, 24-27 September 2009, Bodrum, Türkiye.

“On the Relaxation Time of Polymers in terms of Temperature and Pressure Dependent Hole Fraction”, B. Çoşkun,U. Yahşi and C. Tav, 16. Statistical Physics Days, 25-27 June 2009, Koç University, Sarıyer, İstanbul.

Statistical Termodynamics of Branched and Dendrimer Macromolecular Structures

Uğur Yahşi, Mustafa Aslan and Cumali Tav

Thermodynamic features of macromolecular structures are related to the shape, branching, type and number of intramolecular bonds. Simha and Somyscynky (SS), making use of the statistical thermodynamics theories developed irrelevantly from the structure for macromolecules, designed a model to include the degree of disorder in the lattice model introducing vacancies by means of Flory-Huggins Mean Field Theory (FHMF)[1-2]. However, FHMF theory is just a zeroth order approximation and a model irrelevant from the polymer architectures where the structural factor is not involved. For this purpose, Lattice Cluster Theory (LCT)[2-5], which also figures on polymer architectures, has been developed by Freed et al. In the LCT theory, the systematic evaluation of entropic contribution of self-avoiding and mutually avoiding polymer chains on a lattice has been undertaken and the exact expression is preceded by a cluster expansion for evaluating zeroth order FHMF approximation. Diagrammatic representation of the cluster expansion has been presented to overcome chain connectivity and excluded-volume constraints. 

The correction of the LCT theory to the FHMF theory has been expressed in terms of the occupied site fraction implemented in the SS theory and then introduced in the SS theory. We have thus obtained a structure related modified SS theory to be applied to different polymer architectures, such as hyperbranch and dendrimer polymers, to which the SS model is inapplicable. The hole fraction, essential to the statistical thermodynamics, has been scrutunized and,beginning from MSS and chain structure through dendrimer structure, implemented on the PE, PP, PS and Polybenzylether polymers. When tested with the SS model, the LCT model has produced higher hole fraction values. Through the LCT model, the temperature and pressure dependent convertion of hole fraction for structures capable of branching has been examined.

[1] Flory, P.J.; "Thermodynamics of High Polymer Solutions", Journal of Chemical Physics, 9(8) (1941) 660; ibid, 10 (1942) 51.

[2] Huggins, M.L.: "Solutions of Long Chain Compounds", J. Chem. Phys., 9(5) (1941) 440.

[3] Bawendi, M.G.; Freed, K.F.: " Statistical-Mechanics of the Packing of Rods on a Lattice - Cluster-Expansion for Systematic Corrections to Mean Field", Journal of Chemical Physics, 85(5) (1986) 3007-3022.

[4] Bawendi, M.G.; Freed, K.F.; Mohanty, U.: "A Lattice Model for Self-Avoiding Polymers with Controlled Length Distributions .2. Corrections to Flory-Huggins Mean Field", Journal of Chemical Physics, 84(12) (1986) 7036-7047.

[5] Freed, K.F.; Bawendi, M.G.: "Lattice Theories of Polymeric Fluids", Journal of Chemical Physics, 93(6) (1989) 2194-2203.

Published Papers and Presentations

“Entropic Contribution of Polymer Structure Introducing a Systematic Expansion of Lattice Cluster Theory into Simha-Somcynsky Theory,” M. Aslan, U. Yahşi and C. Tav, Turkish Physical Society, 30. International Physics Congress,, 2-5 September 2013, İstanbul Üniversitesi, Vezneciler, İstanbul, Türkiye.

“Systematically Substitute Coefficients depending on the Polymer Structure into Simha-Somcynsky Lattice-Hole Theory,” M. Aslan, U. Yahşi and C. Tav, Turkish Physical Society, 29. International Physics Congress, 5-8 September 2012, Bodrum, Türkiye.

“Statistical Thermodynamics of Chain Molecular Systems: Introducing A Systematic Expansion of Lattice Cluster Theory into Simha-Somcynsky Theory,” M. Aslan, U. Yahşi and C. Tav, 15. Statistical Physics Days, 19-21 June 2009, Koç University, Sarıyer, İstanbul.

“Modification of Simha-Somcynsky Theory Introducing Structure Related Entropic Contribution of Polymer Lattice Using Lattice Cluster Theory,” M. Aslan, U. Yahşi and C. Tav, 12. Liquid State Symposium, 31 October 2008-2 November 2008, İstanbul University, Baltalimanı, İstanbul.

Completed Thesis

Mustafa Aslan (2009), “Statistical Termodynamics of Branched And Dendrimer Macromolecular Structures,” PhD thesis in Physics, Marmara University, Institute of Graduate Studies in Pure and Applied Sciences, İstanbul.

Surface Tension and Surface Free Volume Depth Profile of Polymers Using Statistical Thermodynamics

Uğur Yahşi, Saygın Küzeci, Cihat Boyraz and Cumali Tav

Surface tension and its density profile of polymers and oligomers play an important role in polymer blending, wetting, coating, adhesion, foaming and a comprehensive role in the description and understanding of many processes. Since half a century, Cahn-Hilliard (CH) describes the free energy profile of polymer surfaces or interphases as a inhomogeneous mixture. CH considers the free energy density to be two folds: the first is the constant free energy density for a homogeneous region of the system and the second is the density gradient contribution to the free energy. The latter is associated with an important temperature dependent parameter as the gradient energy coefficient, . Surface tension can be established by using this free energy, and the gradient energy coefficient parameter can be determined from the surface tension data.

On the other hand, the lattice-hole Simha Somcynky (SS) theory describes the thermodynamic properties of both low and high molecular weights in terms of hole fraction. The surface thermodynamics properties of polymers are strongly correlated with the bulk properties such as inherently hole fraction. A treatise has been made by Carri and Simha as a correlation of surface tension with the hole fraction in the bulk by means of the SS theory. The quantitative success of the SS theory encouraged us to employ in conjunction with the Cahn-Hillard density gradient theory to inspect how the hole fraction changes from the bulk to surface. In this purpose, we have successfully derived the surface energy and the surface depth profile in terms of chemical potential by means of the SS with the Flory-Huggins Mean Field Theory (FHMF) and the Lattice Cluster Theory (higher order contribution to the FHMF).

Published Papers and Presentations

“The Surface Hole Fraction Gradient Profile of Polyethylene Using Simha-Somcynsky and Cahn-Hilliard Theories,” U. Yahşi S. Küzeci and C. Tav, Turkish Physical Society, 28. International Physics Congress, 6-9 September 2011, Bodrum, Türkiye.

“Modeling the Surface Tension of Chain Molecular System using Statistical Thermodynamics,” K. Doruk, T. Şenel, C. Tav and U. Yahsi, İTÜ 12. Statistical Physics Days, 30 June-02 July 2005, İstanbul Technical University, Maslak, İstanbul

Completed Thesis

Saygın KÜZECİ (2011), “On the Extraction of Free Volume Depth Profile of Polymer Surface Using Simha-Somcynsky And Cahn Hilliard Theory,” PhD Thesis in Physics, Marmara University, Institute of Graduate Studies in Pure and Applied Sciences, İstanbul.

Cihat Boyraz (2004), “Interrelationship of Surface Tension with Bulk Properties of Chain Molecular System,”  MSc Thesis in Physics, Marmara University, Institute of Graduate Studies in Pure and Applied Sciences, İstanbul.

Statistical Thermodynamics of Hydrocarbons and Polymer Liquids: Investigation of Ultrasonic Sound Velocity, and Isothermal and Isentropic Compresibility in terms of Free Volume Method

Uğur Yahşi, Ahmet Sayıcı, Semih Aydın

The estimation of the speed of sound in dense chain molecules is an important subject both from the point of their physical specifications and the interrelation of their thermodynamic quantities.  In our treatise the cell model of Lennard-Jones and Devonshire generalized to assemblies of chain molecules due to Prigogine et al. is employed. Simha and Somcynsky (SS) made an arrangement in the model increasing the disorder by introducing the holes in quasi-lattice. Established equation of state was intensively applied to low and high molar mass fluids. Our present interest is to estimate the speed of sound using the latter including other possible degrees of freedom (vibrational, translational and rotational, etc.) into Helmholtz energy for the calculation of the heat capacity of the system.

Estimating the speed of sound necessitates the calculation of isentropic compressibility, thermal expansion and heat capacity. The deviation in the outcome is in a good agreement at high pressure for the thermophysical properties and the speed of sound, but at low pressure the errors are apparently high, say %6 maximum deviation observed in the speed of sound for tridecane. The results are promising and promoting for future study.

Published Papers and Presentations

“The Speed of Sound Estimation in Statistical Thermodynamics of Pure Hydrocarbon Liquids,” A. Sayıcı and U. Yahsi, 6. National Liquid State Symposium, 14-16 June 2002, İstanbul University Baltalimanı, İstanbul.

Completed Thesis

Ahmet Sayıcı (2002), “Statistical Thermodynamics of Hydrocarbon Liquids:Thermodynamic Relationship with Ultrasonic Speed of Sound” MSc in Physics, Marmara University, Institute of Graduate Studies in Pure and Applied Sciences, İstanbul.
Semih Aydın (2002), “Statistical Thermodynamics of Hydrocarbon Liquids: Investigation of Isothermal ve Isentropic Compresibility in terms of free volume,” MSc in Physics, Marmara University, Institute of Graduate Studies in Pure and Applied Sciences, İstanbul.

Statistical Thermodynamics of Chain Molecular Liquids: Scaling Parameters and Their Group Contributions

Uğur Yahşi, Saygın Küzeci and Robert Simha

The thermodynamics of fluids with dense chain molecules is an important subject both from the point of their physical specifications and as it is a generalization of statistical thermodynamics of simple fluids. In our treatise, we are interested in the generalization of cell model of Lennard-Jones and Devonshire. For the first time, Prigogine and his friends generalized this theory of the chain molecule system in both single and multi-component molecule systems.  Simha and Somcynsky (SS) made an arrangement in model increasing the molecular disorder by employing holes in quasi lattice. Established equation of state was applied for polymer and fluids with low molecular mass densely and rather favorable results were obtained.

Our purpose is to reach to generalized principles based on molecule structure. In view of this aim, we would like to determine group interaction energy and characteristic volume parameters of each unit in the molecule structure by using the decomposition equations. We also aim to form the decomposition equations for fluids in the form of a mixture and to test such parameters by using the same method.

Scaling P*, V*, and T* are the characteristic parameters of related polymer fluids. Average interaction parameter and repulsive volume characteristics are obtained from these parameters. These parameters are decomposed into various molecule units, which can occur on the lattice. For this purpose, the necessary equations are solved and resulting parameters are obtained. For determining the validity of results within the mixture, the decomposition equations for the Mixture State were formed. The fluids we use for application are oligometric hydrocarbon fluids.

Published Papers and Presentations

“Statistical Thermodynamics of Hydrocarbon Fluids: Scaling Parameters and Their Group Contributions,” R. Simha and U. Yahsi, J. Chem. Soc. Faraday Trans., 91(16), 2443-2455 (1995) (Citation Index = 12)  

“Equation of State of Alkane and Alkylbenzene Liquids: A Test of the Group Contributions of Scaling Parameters for Physical and Chemical Mixtures,” Ugur Yahsi, Saygın Küzeci, and Mustafa Alevli, Int. J. of Thermophysics, 23(2), 501-512 (2002).

“Statistical Thermodynamics of Hydrocarbon Liquids: Physical and Chemical Mixtures,” Saygın Kuzeci and U. Yahsi, 3. National Liquid State Symposium, 28-30 May 1999, İstanbul University Baltalimanı, İstanbul.

Completed Thesis

Ugur Yahsi (1994), “Statistical Thermodynamics of Chain Molecular Systems: Characteristic Group Contributions,” PhD Thesis, Case Western Reserve University, Dept. of Physics.

 Saygın Küzeci (1999),  “Statistical Thermodynamics of Hydrocarbon Molecular liquids: Investigation of Physical and Chemical Mixtures using Characteristic Group Contributions,” MSc in Physics, Marmara University, Institute of Graduate Studies in Pure and Applied Sciences, İstanbul.