Perforated Monolayers: Design and Synthesis of Porous and Cohesive Monolayers from Mercurated Calixarenes1

Article abstract of DOI:10.1021/ja00203a020

Mercuration of a series of O-alkylated calixarenes (produced via reaction of tetrahydroxycalix<4>arene, pentahydroxycalix<5>arene hexahydroxycalix<6>arene, and heptahydroxycalix<7>arene with n-bromobutane and with n-bromohexadecane) affords an homologous series of calixarene-based surfactants that form stable monolayers at the air-water interface.Surface pressure-area isotherms, measured for each calixarene, yield limiting areas that are in excellent agreement with values predicted from space-filling models, if it is assumed that the base of each calixarene is parallel and the alkyl chains are perpendicular to the water surface.Introduction of malonic acid to the aqueous subphase results in a substantial increase in the coheresiveness of films derived from calix<4>arene-, calix<5>arene-, and calix<6>arene-based surfactants, as judged by changes in surface viscosity.X-ray photoelectron spectroscopic analysis of a Langmuir-Blodgett film, produced from a malonic acid stabilized calix<6>arene monolayer, shows a carboxylate/mercury ratio of 0.9.This value is in excellent agreement with a model that assumes that all of the bound malonate acts as a bridge between adjacent calixarene subunits in an hexagonally packed array.Water evaporation studies, carried out at the air-water interface, reveal that each of the calix<4>arene-, calix<5>arene-, and calix<6>arene-based monolayers, in the presence and in the absence of malonic acid, maintains a porous structure that offers little resistance to the permeation of water, relative to a densely packed aliphatic monolayer of surfactant.