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By using the interaction parameters deduced from small-angle neutron and X-ray scattering, we have calculated, via mean-field theory, the coexistence curve of the semidilute solutions of polystyrene in cyclohexane. We obtain substantial agreement between the theoretical coexistence curve and the observed phase-separation points reported in the literature. General features of the temperature-concentration diagram of polymer solutions in the semidilute poor solvent regime are also discussed.

Small-angle X-ray scattering from semidilute solutions of polystyrene in cyclohexane has been studied in a poor solvent regime. The values of binary and ternary cluster integrals of polymer segments were determined from the concentration dependences of the correlation length and the osmotic compressibility, as obtained from the absolute intensity at zero scattering angle, at various temperatures in the poor solvent regime. By using these interaction parameters the coexistence curve was calculated via a mean field theory. Excellent agreement was achieved between the calculated coexistence curve and the experimental phase separation points which we have measured.

The structure and the structure change of the melt crystallized oligourethanes, CH 3 CO (CH 2 ) 5 NHCO n OCH 3 , having strictly homogeneous molecular weight, were studied. The crystal system of every melt crystallized oligourethane was similar to that of the single crystal of n = 2. In the case of n = 2, crystalline rearrangement by annealing does not occur, although the number of hydrogen bonds increases. On the other hand, rearrangement occurs for n = 3 and higher oligomers. It was considered that the rearrangement for n = 3 was the transformation from the spherulite to the plate-like crystal, whilst for those of n = 6 and 8 the growth of the new spherulitic type of crystal by secondary crystallization occurs. For n = 10 and the polymer crystal the thickening was accompanied by an increase of ordered regions.