Amphiphilic O-functionalized calix[4]resocinarenes with tunable structural behavior

Abstract

Novel amphiphilic calix[4]resorcinarenes oxyethylated at the upper rim and alkylated at the lower rim (CR-CnH2n+1, here n is the number of carbon atoms in the alkyl substituent; n = 2,5,7,8,9,11) were synthesized, and their association behavior in water-organic solvents was explored. Surface properties and the association behavior of CRs were shown to be strongly controlled by their structure and the nature of the co-solvent. Solely CR-C5H11 demonstrates surface activity in the mixed water-DMF and water-DMSO solutions, while no surface activity occurs in the water-THF mixture. The DLS measurements revealed a very low concentration threshold of the aggregation (around 0.01 mM) for the CR series including surface inactive compounds. In water-DMF and water-DMSO solutions the CRs of low hydrophobicity were shown to associate through an open model with the formation of large aggregates of 300-400 nm, while more hydrophobic CRs can associate through a closed model and form rather small micelle-like aggregates of 10 to 20 nm. © 2014 The Royal Society of Chemistry.