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Criteria and the mechanism for the four-phase separation in quaternary systems solventpolydisperse polymer are established. Multiple critical points act as roots of multiphase regions. Thus, a critical point diagram displaying multiple critical points in the global space of all quaternary systems can serve as a basis for classification of their phase behavior. For instance, four-phase equilibria are potentially possible only in systems mapping beyond the quadruple critical line. A four-phase region is invariably tied to the existence of multiple three-phase regions. For instance, in systems with dx/dT < 0, two seemingly independent three-phase regions, TI and TB, grow closer with decreasing temperature, form a linear contact, and T3 penetrates into T1, thus creating the four-phase tetrahedron with four surrounding three-phase regions. Eventually T, is absorbed by T1; at this point the complex phase diagram degenerates into a single three-phase region that evolves then normally.

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Elastomeric networks based on poly[methyl(3,3,3-trifluoropropyl)siloxane] having a minimum level of stereo-regularity crystallize and self-reinforce when stretched at room temperature. The effect is especially pronounced in networks where the cross-links are uniformly spaced. The polymers are made by modification of a recently described anionic ring opening copolymerization of prescribed mixtures of cis- and trans-1,3,5-trimethyl-1,3,5-tris (3′, 3′, 3′-trifluoropropyl) cyclotrisiloxane. This provides polymers enriched in stereoregularity with nearly monodisperse molecular weight distributions and reactive groups at the chain ends. The end-linked networks show markedly enhanced mechanical properties due to self-reinforcement from strain-induced crystallization. In addition to applied strain, self-reinforcement depends on temperature and the amount of stereoregularity introduced to the polymer. Strained specimens having high levels of stereoregularity and pre-existing crystallinity exhibit plastic flow and, upon release of the applied strain, stress-hardening. Wide angle X-ray scattering (WAXS) on strained specimens establishes that, although the relative degree of crystallinity varies, the basic crystal structure is unaltered by cross-linking, amount of strain, or amount of stereoregularity. Unit cell parameters from WAXS indicate a monoclinic crystal and suggest a 4*11 chain conformation.