On the layer structures in acid- and amine-substituted calixarene Langmuir–Blodgett films

• X-ray reflectometry measurements made on LB films of calixarenes.
• Total film thickness and the bilayer spacing were obtained from reflectivity profiles.
• The “pinched loop” molecular conformation found for calix[8]arenes.
• The classical bowl and chain configuration found for calix[4]arenes.

X-ray reflectometry measurements have been made on Langmuir–Blodgett (LB) films of an amine-substituted tertiary octyl calix[8]arene and of alternating layers of acid and amine-substituted tertiary octyl calix[8]arene as well on LB films of alternating layers acid/amine-substituted tertiary butyl calix[4]arenes. The total film thickness and the bilayer spacing were obtained for each sample from its reflectivity profile R(Q) vs. Q. Simulations of the reflectivity profiles were made with a programme based on Parratt's recursive relations, using models of their multilayer structures. The “pinched loop” molecular conformation which, rather surprisingly, describes the layer structure in an acid substituted tert-octyl calix[8]arene, also describes the structures in the amine-substituted and the alternate layer acid/amine-substituted calix[8]arenes, with the exception that the amine head-groups are larger and their interpenetration is prevented. In contrast, the smaller calix bowl in the acid/amine-substituted calix[4]arene molecules defines their conformation more rigidly. The layer structure of the alternate layer acid/amine-substituted calix[4]arene sample is therefore well described by the repetition of the classical bowl and chain configuration.

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