Phase Transitions Within Poly oxyethylene Cholesteryl Ethers-Based Systems

Phase Transitions Within Poly(oxyethylene) Cholesteryl Ethers-Based Systems 

Lopez-Quintela et al. concluded that in case of large chain lengths the behavior was dominated by the EO chain, while for n 10 the rigidity of the cholesterol group dominated, imposing its properties on the surfactants [32]. 

WAXS measurements demonstrated that the two lateral distances for the long-chain surfactants were similar to those of other polyoxyethylene surfactants (3.87 and 4.72A). Thus, the authors concluded that the molecules were packed in the solid state similar to other polyoxyethylenes and that the thermodynamic behavior of the surfactants was mainly governed by the polyoxyethylene chain. Since the lateral distances among the polyoxyethylene chains are smaller than in the cholesterol, the polyoxyethylene chains could be more closely packed in the soUd state only by an antiparallel arrangement, in order that the more voluminous cholesterol moieties do not interfere with each other. However, when the chain was reduced, below n = 10, the cholesterol group rigidity was pronounced, the lateral distances became similar to the lateral distances in the cholesterol, and transformation into a liquid-crystalline phase occurred [32]. 

ChEOn (n = 10 and 15) systems as a function lamellar, and reverse micellar phases, 

For more profound understanding of the phase behavior in these systems, Sato et al. evaluated the hydration levels of the oxyethylene chain in each system [33]. 

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