Microphase separation definition

Such definitive forecasts do not result from the theories of Leibler or Hong and Noolandi. However, the latter theory describes in detail the phase diagram for copolymer — homopolymer mixtures and is therefore pertinent to the X-ray work of Roe Similarly, Leibler s theory provides a detailed description of a microphase separation mechanism and thus is of value in the interpretation of experiments investigating this phenomenon. Small angle neutron scattering data reported to date has been maitily concerned with pure styrene-diene block copolymers which are fully microphase separated and thus examined D, dj, and interfadal layer thickness as a function of molecular weight and composition and therefore comparison has usually been made with the MIA theory of Helfand. 

Both processes that accompany IPN formation - chemical reaction of cross-linking and physical process of microphase separation - proceed simultaneously in the definite time-interval between the onset of phase separation and gel-point of each network. Such superposition results in a complicated microphase structure of IPN. It means that these processes proceed in non-equi-... 

Polymeric surfactants are, by definition, surface active. On the other hand, not all surface active polymers are amphiphilic. In effect, every polymer is surface active in the sense that it shows a strong tendency to adsorb. This, as we discussed, is a consequence of the polymerization the translational entropy per monomer decreases as l/N while the interaction energy between a monomer and the surface is roughly independent of N. Polymeric surfactants are distinguished by their ability to self-assemble because of microphase separation. 

From all that was said above, it follows that the polymer alloy is a comph-cated midtiphase system with properties which are determined by the properties of constituent phases. It is very important to note that if, on the macrolevel, the thickness of the interphase regions is low, as compared with the size of the polymer species, for small sizes of the microregions of phase separation such approximation is not vahd. In comparison with the size of the microphase regions, the thickness of the interphase may be of the same order of magnitude. Therefore, they should be taken into accoiuit as an independent quasi-phase in calculation of properties of polymer alloys. We say quasi-phase because these region are not at equilibrium and are formed as a result of the non-equilibrium, incomplete phase separation. The interphase region may be considered as a dissipative structure, formed in the coiu-se of the phase separation. Although it is impossible to locate its position in the space (the result of arbitrary choice of the manner of its definition), its representation as an independent phase is convenient for model calculations (compare the situation with calculations of the properties of filled polymer systems, which takes into account the existence of the surface layer). 

Obviously, the mechanism of spinodal decomposition, which determines the microphase structure of cured IPN, is not the only mechanism, i.e., separation may also take place by the nucleation mechanism under definite conditions. 

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