Phase separation Terms Links

The gelation of iPS has already been discussed in terms of a phase separation, but there is also strong evidence intimately linking crystallization and gelation. Indeed, the crystallographic structure of the micellar gel crystals is distinctly different from the traditional Natta-Corradini structure and appears to be unique to gels. This new structure has a fibre-repeat close to a fully extended (al -trans) conformation but is actually a 12i helix, in contrast to the 3i-helix of... 

The above represents the classical definition of an IPN. The term interpenetrating polymer network was coined before the extent or conseqnences of phase separation were fully realized. This article covers sequential and simultaneous types of IPNs made in bulk and also includes such materials as IPNs based on latexes and suspension-sized particles thermoplastic IPNs, which contain physical cross-links in one or both polymers, and hence may be (partly) soluble and a number of other closely related materials. 

It is shown that the- angular dependence of the scattered light intensity can give information about correlations in density and orientation and at the same time permits conclusions about the type of orientational order present in the system under investigation. Absolute measurements, however, can add to these a quantitative estimation of the mean square of the polarizability fluctuation, which can be connected with phase separation and inhomogeneous cross-linking and the absolute value of the anisotropy which may be interpreted in terms of the kind of order and the relative parallelity of the chains on a microscale. 

Another kind of mixed network comes about when two linear polymers that are incompatible at room temperature are simultaneously cross-linked at a high temperature at which they are compatible. Phase separation on cooling may be inhibited by the covalent bonds, which limit the movement of polymer chains. The term semi-IPN can refer to a linear polymer trapped in a network of another polymer. 

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