Conformational mobility in alkyl-chains of an anchored bilayer

Abstract

The conformation of alkyl chains in an anchored bilayer formed by the intercalation of cetyl-trimethyl ammonium ions in layered CdPS₃ has been investigated by ¹³C NMR and infrared spectroscopy at different temperatures. The two techniques return widely differing estimates of gauche conformational disorder with the NMR indicating a much greater extent of disorder. Reconciliation of this difference requires that the observed features in the NMR be dynamically averaged. We show from infrared spectroscopy that the nature of disorder in the anchored bilayer is essentially in the form of kinks (gauche-trans-gauche sequences), and if these are mobile along the length of the alkyl chain on time scales faster than 3.5 ms, they would result in the dynamic averaging of features in the NMR.