Solubility and miscibility in ternary systems: polymer liquid crystal + flexible polymer + solvent (original) (raw)
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Liquid crystallinity in flexible and rigid rod polymers
The Journal of Chemical Physics, 2000
We apply an anisotropic version of the polymer reference interaction site model ͑PRISM͒ integral equation description of flexible polymers to analyze athermal liquid crystallinity. The polymers are characterized by a statistical segment length, o , and by a physical hard-core thickness, d, that prevents the overlap of monomers on different chains. At small segment densities, , the microscopic length scale d is irrelevant ͑as it must be in the universal semidilute regime͒, but becomes important in concentrated solutions and melts. Under the influence of the excluded volume interactions alone, the chains undergo a lyotropic, first-order isotropic-nematic transition at a concentration dependent upon the dimensionless ''aspect ratio,'' o /d. The transition becomes weaker as d→0, becoming second order, as has been previously shown. We extend the theory to describe the transition of rigid, thin rods, and discuss the evolution of the anisotropic liquid structure in the ordered phase.
The journal of physical chemistry. B, 2016
The phase boundaries of polymer solutions in mixed solvents can be extremely complex due to the many competing van der Waals and associative interactions that can arise in these ubiquitous and technologically important complex fluids. The present paper focuses specific attention on ternary solutions of polymers (B) dissolved in a mixture of two solvents (A, C) that competitively associate with the polymer. We are particularly concerned with explaining the origin of the peculiar phenomenon of cononsolvency in mixed solvents, where a mixture of two individually good solvents behaves effectively as a poor solvent. Our computations are based on a recently developed generalization of Flory-Huggins theory that incorporates the competitive solvation of a polymer by two associating solvents. On the basis of this framework, we evaluate the limit of polymer phase stability (spinodal curves) and the second osmotic virial coefficient [Formula: see text] as a function of temperature and the comp...
Polymer, 1960
An experimental study is reported of phase equilibria in ternary systems comprising two polymers and one liquid. The measured distribution of the two polymers between two coexisting phases is used, in conjunction with the Flory-Huggins theory, to derive polymer-polymer interaction 'constants'. These can be used to predict the miscibility and heat of mixing of the same polymers in binary mixtures. Experimental studies on fluid polymers show that miscibility is less and heat of mixing larger than predicted. It is concluded that these studies on ternary systems do not afford a reliable guide to the behaviour of binary polymers mixtures. Possible reasons ]or the discrepancy are discussed.
On the miscibility of liquid crystalline polymers
Polymer, 2000
We report on the feasibility of the thermodynamic miscibility of liquid crystalline polymers (LCPs) and their use as a new material approach for the reinforcement of engineering thermoplastics (TPs). In this work, we present the preliminary results of the study on binary model systems consisting of both a wholly aromatic and an aromatic-aliphatic miscible LCP blend. The ultimate goal of this approach is to develop multi-component miscible LCP blends having TP-compatible components which could be useful as processing-aids and reinforcement of TP composites.
Die Makromolekulare Chemie Rapid Communications
In the last few years considerable attention has been paid to the experimental study of the liquid-crystalline ordering of polymers containing stiff and flexible fragments in the main chain1s-4). However, until very recently there was no theoretical work on this problem. Only in 1981 a paper by Matheson and Flory appeareds) (see also ref.6)), in which the well-known lattice method7s8) was used to consider the liquidcrystalline transition in a solution of macromolecules containing in the main chain stiff rods, freely-rotating joints between the rods, and flexible spacers. One of the main simplifications used in ref. 5, was the assumption that the flexibility of flexible spacers is independent of the degree of orientational ordering in the solution. This assumption seems to be inconsistent with reality: it is clear that the self-consistent orientational field connected with the liquid-crystalline ordering influences not only stiff fragments of the chain, but also flexible ones. As a result, in the liquid-crystalline phase flexible fragments should become somewhat oriented along the anisotropy axis.
Phase Equilibria of Flexible Polymer and Monomer Liquid Crystal Blends
Recent Progress in Materials, 2019
In this study, we explored the phase equilibria in blends of a nematic liquid crystal monomer and a nematic liquid crystal flexible polymer within the whole composition of the phase diagram. The crystal-nematic and nematic-isotropic transition temperatures, as well as the transition enthalpies and entropies, indicated the total miscibility in this mesogenic blend system. We also extracted an empirical axial ratio of 4.52 for the polymer from the nematicisotropic transitions of the blends. Further, from the biphasic nematic-isotropic transitions of the blends in low concentration regions, we estimated the entropies of pure monomer and polymer from a theoretical lattice model. The calculated and experimental results showed good agreement. This work will be continued with a more detailed study of phase equilibria and comparison with other theoretical models in nematic flexible polymer and nonmesogenic rigid-rod monomer blends will be made.
Nonequilibrium liquid-liquid phase separation in crystallizable polymer solutions
Macromolecules, 1992
The relation between liquid-liquid phase separation and crystallization was investigated by applying a systematic change in the interaction in isotactic polypropylene (i-PPI solutions with a proper selection of solvents. A series of dialkyl phthalates, with a different number of carbon atoms in the alkyl chain, was used to control the solvent quality. The liquid-liquid phase separation temperature decreased remarkably when the interaction became favorable while the melting point curve remained constant. As the result of this systematic change in polymer-solvent interaction, the liquid-liquid phase separation was observed under nonequilibrium conditions below the equilibrium liquid-solid transition. Liquid-liquid phase separation of the i-PP solutions with strong interaction was probed by using atactic polypropylene (a-PP) in the same solvent systems. The results indicate that although the liquid-liquid phase separation of i-PP solutions with the strong interactions cannot be observed in situ due to the competing crystallization, liquid demixing can occur at a low temperature during rapid quenching. An additional feature oberved under the nonequilibrium conditions was liquid-liquid phase separation induced by crystallization in concentration and temperature regions outside the binodal curve. In polydisperse samples, fractionation during liquid-liquid phase separation resulted in bimodal behavior of the liquid-liquid transition and in deviation of melting points in the biphasic region. symbol alkylgroup M, preaeure(mmHg)4 supplier bp ("C)/ C, butyl 278 3401760 Aldrich C6 hexyl 334 21015 Exxon C7 heptyl 362 22015 Euon CS OCtYl 391 23015 Euon cab 2-ethylhexyl 391 3901760 Aldrich CS nonyl 419 25115 Euon Cio d w l 447 25615 Euon 4 From the information provided by the suppliers.
Macromolecules, 2009
Experimentally obtained islands of immiscibility are reported for the systems PS/PVME/THF at 20°C and for PS/PVME/CH at 55°C (PS: polystyrene, PVME: poly(vinyl methyl ether), THF: tetrahydrofuran, CH: cyclohexane). THF is a good solvent and CH is a marginal solvent for both polymers. In the case of THF, information on the Flory-Huggins interaction parameters of the three binary subsystems suffices for a qualitative prediction of the phase behavior of the ternary system. Quantitative agreement can be achieved by means of composition-independent ternary interaction parameters. For the marginal solvent CH, the exclusive use of binary interaction parameters wrongly predicts complete miscibility of all three components. In this case, one ternary interaction parameter must be treated as a function of composition in order to match experiment and theory. On the basis of the present results, it can be concluded that the preparation of homogeneous mixtures with arbitrary composition from a pair of compatible polymers and a common solvent is only possible on rare occasions.