Semiflexible polymers phase diagram

Phase diagrams of ternary systems containing two semiflexible polymer components 1 and 2 can be calculated from thermodynamic functions given by Eqs. 26-28. The thick solid curves and thin solid segments in Fig. 9 are calculated binodals and tie lines, respectively [17]3. In the calculation, the diameter... 

This article deals with some topics of the statistical physics of liquid-crystalline phase in the solutions of stiff chain macromolecules. These topics include the problem of the phase diagram for the liquid-crystalline transition in die solutions of completely stiff macromolecules (rigid rods) conditions of formation of the liquid-crystalline phase in the solutions ofsemiflexible macromolecules possibility of the intramolecular liquid-crystalline ordering in semiflexible macromolecules structure of intramolecular liquid crystals and dependence of die properties of the liquid-crystalline phase on the microstructure of the polymer chain. 

Now let us discuss the applicability of the results obtained for other models of semiflexible macromolecules. It is clear that the qualitative form of the phase diagram does not depend on the model adopted. The low-temperature behavior of the phase diagram is independent of the flexibility distribution along the chain contour as well, since at low temperatures the two coexisting phases are very dilute, nearly ideal solution and the dense phase composed of practically completely stretched chains. The high temperature behavior is also universal (see Sect. 3.2). So, some unessential dependence of the parameters of the phase diagram on the chosen polymer chain model (with the same p) can be expected only in the intermediate temperature range, i.e. in the vicinity of the triple point. 

Schubert, F. Friedrich, K. Hess, M. Kosfeld, R., "Investigations on Phase Diagrams of a Coil-Polymer (PC) and a Semiflexible Thermotropic Mainchain Polymer (PET-co-PHB) in Solution," Mol. Cryst. Liq. Cryst., 155, 477 (1988). 

Fig. 12. Phase diagram for semiflexible polymer and fully flexible polymer. Circles are results for flexible polymers, and diamonds are results for semiflexible polymers. Both systems have a chain length n = 100. The bending energy penalty for the semiflexible polymer is = 5.

Fig. 14. Liquid-liquid phase diagram for a mixture of semiflexible and flexible polymers at constant pressure. The chain lengths of both species are n = 200.

Figure 14 shows the phase diagram of a flexible-semiflexible polymer blend at a constant pressure. Theoretical calculations and experimental results show that such mixtures can exhibit an isotropic-isotropic and isotropic-nematic phase separation. Our calculations are able to capture the isotropic-isotropic phase separation and serve to show that the origin of such a transition can be purely entropic. 

In order to get rid of undesired lattice effects like the almost cuboid form of the most compact adsorbed conformations in the subphases of AC2 in the phase diagram of a polymer on a simple-cubic lattice (see Fig, 13.2), we now investigate the stmcture of conformational phases of a semiflexible off-lattice polymer near an attractive substrate [304,307,308]. 

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