Polystyrene thermodynamics

Gunduz, S. Dincer, S., "Solubility Behaviour of Polystyrene Thermodynamic Studies Using Gas Chromatography," Polymer, 21, 1041 (1980). 

Oels, H. J., and Rehage, G., Pressure-volume-temperature measurements on atactic polystyrene thermodynamic View, Macromolecules, 10, 1036-1043 (1977). 

ATACTIC POLYSTYRENE. THERMODYNAMIC PROPERTIES OF POLYMERS-PART 7. 

Polystyrene thermodynamic and hydrodynamic properties in dilute solution and melt viscosity studied and compared with corresponding linear fractions. Macrocyclic fractions with 1.9 x 10 < M < 3.9 x 10 [225]... 

Gehlsen MD, Bates FS (1993) Heterogeneous catalytic hydrogenation of polystyrene thermodynamics of poly(vinylcyclohexane) containing diblock copolymers. Macromolecules... 

The non-bonded interaction energy, the van-der-Waals and electrostatic part of the interaction Hamiltonian are best determined by parametrizing a molecular liquid that contains the same chemical groups as the polymers against the experimentally measured thermodynamical and dynamical data, e.g., enthalpy of vaporization, diffusion coefficient, or viscosity. The parameters can then be transferred to polymers, as was done in our case, for instance in polystyrene (from benzene) [19] or poly (vinyl alcohol) (from ethanol) [20,21]. 

When this procedure is applied to the data shown for polystyrene in Fig. 116 and to those for polyisobutylene shown previously in Fig. 38 of Chapter VII, the values obtained for t/ i(1 — /T) decrease as the molecular weight increases. The data for the latter system, for example, yield values for this quantity changing from 0.087 at AT-38,000 to 0.064 at ilf = 720,000. This is contrary to the initial definition of the thermodynamic parameters, according to which they should characterize the inherent segment-solvent interaction independent of the molecular structure as a whole. 

Thermodynamic parameters deduced as described above are shown in Table XLI for polyisobutylene and for polystyrene. It will be recalled that these primary parameters are obtained only with consider-... 

Fig. 13. Slope of the power-law region for narrowly distributed polystyrene in (O) trans-decalin (thermodynamically poor solvent) and ( ) toluene (thermodynamically good solvent). (-) theoretical course for a 9-solvent... 

In colloid science, colloidal systems are commonly classified as being lyophilic or lyophobic, based on the interaction between the dispersed phase and the dispersion medium. In lyophilic dispersions, there is a considerable affinity between the two constituent phases (e.g., hydrophilic polymers in water, polystyrene in benzene). The more restrictive terms hydrophilic and oleophilic can be used when the external phase is water and a nonpolar liquid, respectively. In contrast, in lyophobic systems there is little attraction between the two phases (e.g., aqueous dispersions of sulfur). If the dispersion medium is water, the term hydrophobic can be used. Resulting from the high affinity between the dispersed phase and the dispersion medium, lyophilic systems often form spontaneously and are considered as being thermodynamically stable. On the other hand, lyophobic systems generally do not form spontaneously and are intrinsically unstable. 

Finally, we should mention the phenomenon of incompatibility of mixtures of polymer solutions. It applies to nearly all combinations of polymer solutions when the homogeneous solutions of two different polymers in the same solvent are mixed, phase separation occurs. For example, 10% solutions of polystyrene and poly(vinyl acetate), each in benzene, form two separated phases upon mixing. One phase contains mainly the first polymer, the other phase mainly the second polymer, but in both phases there is a certain amount of the other polymer present. This limited compatibility of polymer mixtures can be explained thermodynamically and depends on various factors, such as the structure of the macromolecule, the molecular weight, the mixing ratio, the overall polymer concentration, and the temperature. 

If two different polymers can be dissolved successfully in a common solvent, a molecular intermixing of the dissolved macromolecules should occur due to the fast establishment of the thermodynamic equilibrium. The difficulty with this procedure is due to the fact that very many polymers become incompatible above a certain concentration when their solutions in a common solvent are combined. This means that the originally homogeneous solutions of polymers A and B separate into two phases when being combined, whereby each of the phases contain different quantitative proportions A B [e.g., polystyrene and poly(vinyl acetate) in toluene]. But even when two polymers have been dissolved sue-... 

It is postulated that the main thermodynamic driving force for particle adsorption at the liquid-liquid interface is the osmotic repulsion between the colloidal particles and hydrophilic starch polymer molecules. This leads to an effective depletion flocculation of particles at the boundaries of the starch-rich regions. At the same time, the gelatin has a strong tendency to adsorb at the hydrophobic surface of the polystyrene particles, thereby conferring upon them some degree of thermodynamic... 

Tager and co-workers (51) have invoked bundle structures to explain correlations between the viscosities of concentrated polymer solutions and the thermodynamic interactions between polymer and solvent. They note, for example, that solutions of polystyrene in decalin (a poor solvent) have higher viscosities than in ethyl benzene (a good solvent) at the same concentration, and quote a number of other examples. Such results are attributed to the ability of good solvents to break up the bundle structure the bundles presumably persist in poor solvents and give rise to a higher viscosity. It seems possible that such behavior could also be explained, at least in part, by the effects of solvent on free volume (see Section 5). Berry and Fox have found, for example, that concentrated solution data on polyvinyl acetate in solvents erf quite different thermodynamic interaction could be reduced satisfactorily by free volume considerations alone (16). Differences due to solvent which remain after correction for free volume... 

Berry,G.C. Thermodynamic and conformational properties of polystyrene. II. Intrinsic viscosity studies in dilute solutions of linear polystyrenes. J. Chem Phys. 46,1338-1352(1967). 

Quadrat, O., PodneekaJ. Influence of the thermodynamic quality of a solvent upon the viscosity of moderately concentrated polystyrene solutions. Collection Czech. Chem. Commun. 37,2402-2409 (1972). 

To test theory one must work with solutions for which adequate thermodynamic data exist. Figure 7 contains the state diagram of the same polystyrene with mixtures of methyl isobutyl ketone and Figure 8 with toluene. The similarity... 

For these measurements, temperature has been varied between 55 and 110° C. In this temperature range, the solvent viscosity changes by a factor three 4.7 to 1.5 cps). It is very improbable that a noticeable internal friction factor would change just by the same factor. Moreover, as has already been pointed out at the end of Section 5.2.2, the curves obtained by plotting cot2 c vs reduced shear stress fjN are practically coinciding for dilute solutions of cellulose tricarbanilate fractions with M S 500,000 and for anionic polystyrenes. So one can conclude that the internal friction of the thermodynamically stiff molecules of cellulose tricarbanilate must be rather low. 

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