Fluorinated segments

These structures are well defined by conducting the polymerization in the presence of appropriate mono- and difunctional reagents. They are of considerable interest for the preparation of segmented block copolymers.24,25 For instance, the fluorinated macrodiols 21 have already been used to prepare an interesting new series of partially fluorinated segmented polyurethanes,26 and we are investigating other novel polymers that can be prepared from these intermediates. 

Typically, relatively long fluorinated segments (C F2 +i with n = 4—12 in most cases) were used in the LC molecules, and therefore we focus attention on these perfluoroalkanes. Perfluoro-n-hexane, as a representative example for this type of... 

Fig. 39 Examples of triphenylene based disc-like molecules incorporating fluorinated segments in their peripheral chains (77° C) [267, 268]...

Another feature of the large honeycombs is the nano-phase segregation within the cylinders. The fluorinated segments congregate in the center while the alkyl spacers line the interior of the cylinder walls. This core-shell-in-cylinder... 

A combination of fluorinated segments and siloxane groups was used by Mehl et al. for the terminal-terminal and lateral-lateral interconnection of rod-like mesogens (e.g., compound 206). In contrast to the usually observed smectic phases... 

Fig. 67 Selected examples of rod-like dimesogens with fluorinated segments ( //" C) [353-362]...

Polymers with fluorinated segments represent a field on its own which is not considered here [382-384], Polymer chains were also used to interconnect fluorous mesogenic units, either comprising a single aromatic unit [385-389] or a rod-like units which can be attached either terminally [193, 390-394] or laterally [240, 395-397] to the polymer backbone. In most cases the termini of the mesogenic units... 

Takakura et al. [82] investigated on the structure and the mechanical properties of fluorinated segmented poly(urethaneurea)s, showed that their structures were highly ordered and such polymers behaved as elastomers. 

The polysulfonyl fluoride is soluble in alcohol and moldable by thermoplastic methods. It can be cast into films before or after hydrolysis to produce membranes trade-named NAFION (= Na-fluorinated ion exchanger). In contrast to sulfonated polystyrene-based membranes, that become water-soluble at a sulfonation degree of 25% (i.e. at one sulfonic group per 32 carbons) and have to be cross-linked to prevent their dissolution, Nafion membranes, due to the hydrophobic interaction of the fluorinated segments, are water-insoluble even at a content of one —S03H per 20 carbons in the chain. 

Amato, C. Galas, R A novel leiparvarin analogue possessing a fluorinated segment. Synthesis 2003, 17, 2709-2712. 

PS-fc-PI diblock copolymers [65], poly(fumarate)s or poly(acrylate)s [131], lamellar structures are found in nearly all cases if the number of m is not too small. The backbone and its flexibility seem to have only marginal influence. In simple terms, the strong phase separation into areas with fluorinated segments and areas with the nonfluorinated rest seems to be the first principle in structure formation. Whereas in sf alkanes besides lamellar structures also hexagonally packed cylinder structures are possible [128], the attachment of the. segments as side chain onto the polymer backbone prevents structure modifications with other symmetries. 

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