Fluorocarbon-hydrocarbon diblock compounds

Fluorinated surfactants (or fluorosurfactants, i.e., surfactants with hydrophobic tails comprising a fluorocarbon moiety) provide an alternative means of achieving extremely stable PFC emulsions, as they can provide very low PFC/water interfacial tensions [cr , another factor in Eq. (2)]. d s yet, this option has not been developed, in part because of the added cost involved in the evaluation for approval of a novel active excipient. A further means of effectively increasing the stability of EYP-based PFC emulsion consists of supplementing standard phospholipids with mixed fluorocarbon-hydrocarbon diblock compounds, such as 14 or 15. Such diblocks, which have fluorophilic-lipophilic amphiphilic properties, are expected to improve the adhesion of the phospholipid film onto the PFC droplet. 

Formulations containing small percentages of highly lipophilic fluorocarbon-hydrocarbon diblocks are also being explored. It has been proposed that the diblock compounds are interfacially active at fluorocarbon/water interfaces and orient in such a way so as to extend their fluorinated portion into the FC phase, and... 

If pushed to an extreme the perfluorinated bridge concept can be used to obtain liquid crystals with no cyclic moieties in their mesogenic core structure [4-8]. Since the beginning of the 1980s it has been known that semi-fluorinated n-alkanes, so-called diblock compounds, F(CF2) (CH2) H, form smectic phases [49], because of microphase separation as a result of separate, layer-like aggregation of the hydrocarbon and fluorocarbon moieties. Nevertheless, if introduced into a nematic host mixture, even small quantities of these diblocks cause gelation of the mixture. Their solubility is also limited to a few percent by weight. 

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