Structure and dynamics of polyelectrolyte-surfactant complexes as revealed by solid state NMR

✍ Scribed by Markus Antonietti; Detlev Radloff; Ulrich Wiesner; Hans Wolfgang Spiess

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 959 KB
• Volume: 197
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.1996.021970910

✦ Synopsis

Abstract

^13^C‐CP/MAS‐NMR (__c__ross‐__p__olarization __m__agic __a__ngle __s__pinning), 2D‐WISE (__wi__deline __se__paration experiment) and ^1^H‐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‐C~18~ and PSS‐C~14~. The strong mobility differences between the ionic and alkyl phase in the lamellar complex PSS‐C~18~ 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. ^1^H‐spin diffusion experiments allow to estimate the distance between mobile and immobile regions of the sample. For the complex PSS‐C~14~, the length scale determined by NMR is essentially that of the primary lamellar structure. For PSS‐C~18~, a characteristic length of the density fluctuations within the proposed undulated lamellar structure is estimated.