Interdigitation of an Intercalated Surfactant Bilayer

Abstract

The cationic surfactant cetyltrimethylammonium (CTA) has been ion-exchange intercalated from an aqueous solution of the surfactant by a two-step process into the galleries of layered cadmium thiophosphate to give Cd 0.83 PS 3 (CTA) 0.34 . Two phases of the intercalated product are observed. One is a phase characterized by a lattice expansion of 26.5 Å, in which the methylene chains of the CTA ion adopt a tilted bilayer arrangement. This phase, when left in the reaction media, transforms to a phase characterized by a lattice expansion of 12.5 Å with no change in chemical stoichiometry. Using X-ray diffraction and orientation-dependent infrared spectroscopy, it has been possible to establish that the observed collapse of the interlayer spacing is a consequence of the interdigitation of the methylene "tails" of the intercalated CTA ion. Infrared, Raman, and 13 C NMR spectroscopies have been used to establish the conformation of the methylene chains in the intercalated normal bilayer and interdigitated bilayer phases of Cd 0.83 PS 3 (CTA) 0.34 and the dispersion of the delocalized methylene wagging (ν 3 ) and rocking-twisting (ν 8 ) modes as a probe of the planarity of the chains. The results indicate that a majority of the methylene chains in the intercalated interdigitated bilayer adopt an all-trans planar conformation, whereas, in the normal bilayer phase of Cd 0.83 PS 3 (CTA) 0.34 , although a majority of the methylene units are in a trans configuration, the presence of a few gauche defects is sufficient to destroy the planarity of the methylene chain. Planarity of the methylene chains is the key factor for the absence or occurrence of interdigitation of the intercalated surfactant bilayer.

Dynamics of Alkyl Chains in Monolayer-Protected Au and Ag Clusters and Silver Thiolates: A Comprehensive Quasielastic Neutron Scattering Investigation

“…Upon melting, the IR spectra in all the cases manifest peaks at 1297 cm -1 due to W(g-t-g) kink defects. 56,57 Upon melting, the C-S(g) is more pronounced in AgOT and the conformation is preserved upon cooling back to room temperature. All of these collectively indicate that this system is distinctly different.…”

Structure and photoluminescence of di-amidosil nanohybrids incorporating europium triflate

“…The features at 2925 and 2857 cm −1 are ascribed to the s CH 2 fundamental and to the Fermi resonance between the s CH 2 fundamental with the many overtones of the CH 2 bending vibrations, respectively, and are characteristic of disordered alkyl chains [14][15][16]. The intense 2890 cm −1 event is associated with the a CH 2 stretching mode of alkyl chains in the amorphous state [14][15][16]. We may infer from these results that the alkyl chains of the di-amidosil materials are fully disordered, as suggested by the XRD and DSC data discussed above, and adopt, as expected, essentially gauche conformations.…”

Nanoscopic Photoluminescence Memory as a Fingerprint of Complexity in Self‐Assembled Alkyl/Siloxane Hybrids

“…[13,20] The monoamidosil room-temperature Fourier transform (FT)-Raman spectrum (not shown) exhibited two bands, at 2881 cm -1 (vS) and 2845 cm -1 (S), ascribed to the m a CH 2 and m s CH 2 modes of all-trans conformers of alkyl chains, respectively. [20][21][22] The intensity ratio (r) of these bands is sensitive to the conformational disorder of the alkyl chains and their packing arrangement. [23] The r value (1.60) was of the order of magnitude of those reported for crystalline n-alkanes and solid palmitic acid.…”

“…Moreover, the FT-Raman C-C skeletal stretching region exhibited the characteristic pair of bands of all-trans conformations at 1127 and 1062 cm -1 , but not the band typical of the interruption of alltrans conformations expected at 1080 cm -1 . [22] Analysis of the FTIR amide I and amide II regions (see Supporting Information, Fig. S2) provides information on the relative arrangements of the CO groups.…”