Thermodynamics of Polymers

Polymer thermodynamics is a supporting science that has proved to be very successful owing to its intensive interactions with neighbouring disciplines. The future of polymer thermodynamics will thus strongly depend on developments made in these neighbouring research areas [59]. 

This chapter presents the basics of polymer thermodynamics and some important thermodynamic models, which can be useful for the design/understanding of the processes and the products discussed above and many others. 

Section 16.3 reviews the basics of polymer thermodynamics, discusses the differences compared to thermodynamics of systems having only low-molecular-weight compounds, and finally gives an overview of the Flory-Huggins model, which has been considered one of the cornerstones of polymer thermodynamics. 

Some of the future challenges in the area of polymer thermodynamics will involve the following ... 

Closer collaboration with indnstry, e.g., for testing existing theories for polymers with novel strnctnres, for commercial polymers for which so far the structure is not revealed to academic researchers, and for many other applications of practical interest. Many indnstrial systems are much more complex than the systems studied in academia. Closer collaboration in the future between academia and the polymer and paint/adhesives indns-tries may farther help the advancements in the area of polymer thermodynamics in the coming years. 

This remarkably simple expression is the famous Floiy-Hug ns equation for the Gibbs free energy of mixing, which has been the cornerstone of polymer thermodynamics for more than five decades. 

Since this chapter is not intended to be a review of polymer thermodynamics, but to provide information on diverse thermodynamic aspects pertinent to polymer blends, only EoS derived by Simha and Somcynsky [1969], will be discussed in some detail. 

The derivation of the phase relationships for quasi-binary solutions is given in textbooks of polymer thermodynamics [1,2]. Here, the results necessary for the subsequent discussion are summarized. 

Van Dijk, M.A. and Wakker, A. (1997) Concepts of Polymer Thermodynamics, Technomic Publishing Co., Lancaster, PA. 

Polymer thermodynamics is a supporting science that proved to be very successful due to it s intensive interactions with neighbouring disciplines (such as process optimization, polymer chemistry and chemical modification, polymer characterization, morphology and interface sciences, but also with areas as polymer processing and material science). The future of polymer thermodynamics thus will strongly depend on developments made in these neighbouring research area s. I thus will present a kind of outlook for polymer thermodynamics and the possibilities of compressed or supercritical media, based on some pioneering research results in polymer chemistry and the reported molecular architectures obtained. 

Consider now polymer-based materials from the point of view of a materials user. A user can be an industrialist who buys truckloads of polymer-based components for his plant, a housewife, a little girl playing with a plastic doll—in fact anybody. The user typically has no interest (and little knowledge) of chemical synthesis of polymers, thermodynamics, polymer processing—in fact of any... 

A key feature of any polymer is how it responds to heating. For example, a polymer that on heating becomes much more flexible, perhaps even fluid, can be shaped or molded into a particular form at high temperatures and then rigidified upon cooling so as to maintain the new shape. Processability issues such as these are crucial in polymer science. As with most topics in this field, we cannot hope to cover all aspects of polymer thermodynamics. Here we simply introduce a few key terms that are commonly used and provide valuable initial insights into a polymer s characteristics. 

Long chain branched polyethylene, commonly termed low density polyethylene typifies this class of polymers. Thermodynamic measurements, such as heat capacity (148,149) and specific volume,(150,151) indicate that long chain branched... 

The same as classic thermodynamics, polymer thermodynamics is function of pressure, temperature and composite. But in many cases, pressure effects on polymer thermodynamics was neglected, because polymer thermodynamics were often studied under atmosphere. The classic theory of polymer thermodynamics is Flory-Huggins hard lattice theory. In this theory, the hard lattice is incompressible. A rigorously incompressible system should be unaffected by pressure. However, since experimental results show that the critical temperature for polymer demixing system is strongly affected by pressure, it is clear that polymer containing systems show significant departures from this ideal limit. We wish... 

It is perhaps advisable to reiterate here that all of the thermodynamic analysis of SANS data is based on a mean-field theory, essentially that of Flory and Huggins, and this is known to be inadequate. It may be that, if a proper account were taken of the different expansibilities of the polymer mixture components, as in equation-of-state or lattice-fluid theories of polymer thermodynamics, then the dependencies on microstructure and a g-dependent % might disappear. 

It would be difficult to enumerate all Ron s scientific achievements in the field of polymer thermodynamic. One can name the generalizations of the Flory-Huggins Gibbs energy leading to the prediction and experimental verification of coexistence of three phases in pseudobinary system with sufficiently broad distribution or, the analysis of the functional form of the interaction term leading to the appearance of off-zero critical concentration , at variance with zero critical concentration associated with theta-temperature. Thanks largely to Ron, polymer scientists realize that the cloud point curve is not the binodal and its maximum or minimum are not identical with the critical temperatures. 

CL. Strazielle Docteur s-Sciences, University of Strasbourg, France (1966). Laboratory Institut C. Sadron (CRM), CNRS, Strasbourg (since 1961). Field of interest Physicochemical properties of polymer solutions (dilute and semidilute solutions = Characterization of polymers, thermodynamic of solutions and conformation of polymers - Ternary systems Polymer - polymer - solvent and polymer - solvent - solvent. 

Prof. Bernhard A. Wolf obtained his PhD in the field of Physical Chemistry (Dr. phil.) at the Univeisity of Vienna (Austria) with Prof. Dr. J. W. Breitenbach in 1965. From then until 1969 he was Hochschulassistenf at this Institution. After that he spent a year at the Johannes Gutenbeig-Universitat Mainz (Germany), where he became a scientific assistant (Wissenschaftlicher Assistent ) and performed research work in the field of polymer thermodynamics imder the guidance... 

---