Order-disorder transitions mean molecular weight

In the original analysis, it was understood that this theory should not be applied near the critical point. Mean-field theories ignore concentration fluctuations at distances other than q = q. Near the critical point, concentration fluctuations on very large length scales become increasingly important. A modiflcation to this theory that includes concentration fluctuations has been developed (Fredrickson and Helfand, 1987). A critical point is not predicted by the fluctuation theory, rather a first-order phase transition is predicted for all compositions. A molecular weight dependence is found for /A, which delineates the ordered from the disordered phase shown below for the symmetric diblock copolymer ... 

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