ISSN:
1022-1352
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
13C-CP/MAS-NMR (cross-polarization magic angle spinning), 2D-WISE (wideline separation experiment) and 1H-spin diffusion experiments allow to gain new insight into the structure and dynamics of solid polyelectrolyte-surfactant complexes, a material with pronounced mesophase formation. Experiments were performed on two different complexes of polystyrene sulfonate and octadecyltrimethylammonium or tetradecyltrimethylammonium counterions, PSS-C18 and PSS-C14. The strong mobility differences between the ionic and alkyl phase in the lamellar complex PSS-C18 are reflected in the NMR behavior: in the surfactant tails, a mobility gradient towards the terminal methyl group is observed. This fact as well as a high content of gauche conformations suggest a non-interdigitating morphology of the tails at room temperature. The behavior changes during cooling below an endothermic transition centered at 255 K where a high trans content and a homogenization of the side chain dynamics is observed. We attribute this transition which is invisible in the X-ray experiments to the formation of a highly transoid, interdigitated phase of the surfactant tails which is however not crystallized in a classical sense. 1H-spin diffusion experiments allow to estimate the distance between mobile and immobile regions of the sample. For the complex PSS-C14, the length scale determined by NMR is essentially that of the primary lamellar structure. For PSS-C18, a characteristic length of the density fluctuations within the proposed undulated lamellar structure is estimated.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1996.021970910
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