Compositionally modulated phase in crystalline n-alkane mixtures.
We report an x-ray scattering study of the compositionally modulated microphase separated state (muPSS) of binary n-alkane (C23H48:C28H58) mixtures. By employing a quenching technique, we obtained many orders of sharp lamellar and superlattice reflections. The muPSS is a regular superstructure consisting of pure C23 layers, and layers rich in C28 but containing up to approximately 14% C23 plus voids. A monolayer of the minority component regularly alternates with one or more layers of the majority. The mechanism for thermodynamic stability of the muPSS may be related to the entropy associated with longitudinal displacements of the molecules.
Sirota
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Corporate Strategic Research, ExxonMobil Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801, USA. Eric.B.Sirota@ExxonMobil.com