ISSN:
0947-3440
Keywords:
Thermotropic and lyotropic phase behavior
;
Amphotropes
;
Surfactants
;
Liquid crystals
;
Chromophores
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
New ammonium amphiphiles having a N,N-dimethyl-N-hydroxyethylammonium headgroup and various azobenzene mesogenic units connected by a decyl or dodecyl spacer have been synthesized. The azobenzene unit is functionalized at the 4-position with a cyano, methoxy or fluoro substituent. For the cyano-substituted amphotropes and the fluoro compound with a dodecyl spacer a smectic phase is formed as was observed by differential scanning calorimetry and polarization microscopy. Complexation with sodium dodecyl sulfate, SDS, in a 1:1 molar ratio induces the formation of a smectic phase for the compounds with a decyl spacer. The compounds with a dodecyl spacer showed rather complex behavior attributed to different crystal morphologies. The ammonium amphotropes form aggregates in water when heated above their Krafft temperature. However, these aggregates are not stable and crystallize upon cooling. The ion pair amphiphiles with SDS as second component form vesicles in water as observed by optical and electron microscopy. The observed blue shift in the UV absorption maximum of the amphotropes upon addition of SDS indicates π-π stacking between mesogenic units resulting from aggregation.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.199719970813
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