Sir Samuel Edwards: A sketch on the background of scientific revolution

The scientific contribution of late Professor Sir Sam Edwards and its relationship to the scientific revolution in polymer physics as well as some characteristic features of Sir Edwards as a great scientific character are shortly described and discussed.     

Gyroid symmetry and phase diagram of weak crystallization

The phase diagram in the (τ-δ) plane, where τ is the reduced temperature and δ is a parameter characterizing the anisotropy of the fourth vertex of the effective Hamiltonian, is constructed on the basis of the standard mean-field approximation of the theory of weak crystallization. It is shown that the region of the gyroid phase dominates the phase diagram for intermediate values of the parameters τ and δ. An expression is obtained for the free energy of the gyroid phase. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 6, 436–440 (25 March 1996)     

Microphase separation in multiblock copolymer melts: Nonconventional morphologies and two-length-scale switching

The phase behavior of AfmN(BN2AN2)B(1-fmN) multiblock copolymer melts is studied within the weak segregation theory. The interplay between ordering on different length scales is shown to cause dramatic changes both in the ordered phase symmetry and periodicity upon small variation of the architectural parameters of the macromolecules. Phase diagrams are presented in the (f,chiN) plane (chi is the Flory-Huggins parameter) for various values of the architecture parameters n and m. Near the critical surface, i.e., for (f-0.5)2<1, such nonconventional cubic phases as the face-centered cubic (FCC), simple cubic (SC), (double) gyroid, and the so-called BCC(2) (single gyroid) are found to be stable. The lamellar morphology is shown to be replaced by BCC2, FCC, or SC (depending on the structural parameters) as the most stable low-temperature phase.     

The global phase behavior of the two-component systems with intracomponent association: Flory approach

Within the Flory approach we study the phase diagrams of two-component fluids, the molecules of each component A(f(A)), B(f(B)) bearing f(A) (f(B)) functional groups capable of forming thermoreversible A-A and B-B bonds. We develop a general procedure to classify these diagrams depending on the values of four governing parameters -- entropies and normalized energies of A-A and B-B bonds, and give full topological classification of phase diagrams with f(A,B)> or =3. We show that these phase diagrams can have immiscibility loops and up to four critical points.     

Void Microstructuring in Lamellar Phase of Amphiphilic Macromolecules

The free volume (voids) distribution in the lamellae of the conventional symmetric and amphiphilic diblock copolymers is studied via Monte–Carlo simulation based on the standard bond fluctuation model. Both in the conventional and amphiphilic block copolymers the voids are found to concentrate on the interfaces between the incompatible units, the magnitude of the effect being unexpectedly significant. A crystalline‐like ordering of voids with increase of the incompatibility between the different repeated units in amphiphilic copolymers is first reported and implications of this peculiarity for the morphology and mechanical properties of the amphiphilic copolymers are discussed.

     

Phase equilibrium and charge fractionation in polyelectrolyte solutions

A new type of phase separation in the polyelectrolyte solutions consisting of several types of charged macromolecules differing in their degree of ionization is presented. Via a general thermodynamic consideration we show that even a small difference in the degree of ionization of otherwise equivalent high‐molecular components results in their spatial separation occurring upon decreasing the temperature much earlier than precipitation of any of the pure components from the solution. Some implications of charge fractionation are discussed, including the separation of DNA (or RNA) strands interacting with different proteins and the appearance of heterogeneities in polyelectrolyte solutions of partially charged hydrophobic chains with polydispersed charge distributions such as sodium polystyrene sulfonate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3003–3009, 2007     

Contribution to the statistical theory of solutions of polymers in a critical solvent

The thermodynamics of high polymers in equilibrium with a low-molecular solvent with a large correlation radius (super-and near-critical solvent) is studied. Special attention is devoted to the analysis of typical phase diagrams describing the conditions of solubility of a polymer in such a solvent. The nature of these diagrams is determined by the existence of long-range multiparticle attraction between the monomers, which increases as the critical point of the solvent is approached. At the critical point the contribution of this attraction to the free energy of the system is nonanalytic with respect to the polymer concentration. It is shown that the nontrivial dependences of the polymer-polymer and polymer-solvent coupling constants, which appear in the phenomenological analysis, on the pressure and temperature of the solvent play an important role in the quantitative analysis of the phase diagrams of the solubility of the polymer. These dependences are found in explicit form under the assumption that in the absence of intermonomer bonds the system can be described as a compressible two-component lattice alloy. The partition function of the system under study is represented as a functional integral over two coupled, strongly fluctuating fields, one of which, describing the fluctuations of the polymer density, is the 0 component. By virtue of the specific nature of the problem, the effective temperature corresponding to the 0-component of the field cannot be specified independently, but can be determined by minimizing the total free energy of the system. Zh. éksp. Teor. Fiz. 114, 910–929 (September 1998)