US EPA

3860191 

Journal Article 

STRUCTURE OF THE ISOTROPIC, NEMATIC, AND LAMELLAR PHASE OF A SOLUTION OF TETRAMETHYLAMMONIUM PERFLUORONONANOATE IN D2O 

Froba, G; Kalus, J 

1995 

1 

Journal of Physical Chemistry
ISSN: 0022-3654 

99 

39 

14450-14467 

WOS:A1995RX87500038 

A 30% by weight solution of tetramethylammonium perfluorononanoate in D2O (TMAHFN; C8F17COON-(CH3)(4)) is in a lamellar state below 33 degrees C. In this state the repeat distance and the thickness of the perfluoronated part of the micellar lamellae are around 7.11 and 2.14 nm, respectively, In the presence of a strong magnetic field of 2.0 T a slow reduction of the sample temperature from 40 degrees C (isotropic phase) via 34 degrees C (nematic phase) down to 25 degrees C gives a strong alignment of the nematic and lamellar liquid crystalline phases. By small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) experiments, an order parameter, the mean scattering length density across the lamellae, the structure factor related to the one-dimensionality of the lamellar phase, and information about the perforation of the lamellae could be extracted. A model taking into account all these effects quantitatively describes the experimental scattering intensity distribution in reciprocal space (($) over right arrow Q space) accessible in our experimental setup. Furthermore, for the nematic phase we can extract detailed data on the anisotropic correlation between neighboring discotic micelles. The scattering intensity distribution of the isotropic phase can be described quite satisfactorily again assuming disklike micelles, where the perfluoronated part of the micelle has a thickness of 2.4 nm and a radius of about 3.0 nm.