Syntheses and binding properties of polymeric calix[4]crown-4

Three new polymers containing pendant calix[4]crown-4 units have been synthesized via radical initiated reactions involving a vinylic monomer 7 (5,7,11,23 -tetra-tert-butyl-25- [2-(Acryloxy)ethoxy]-27-methoxycalix [4]arene-crown-4) and with styrene. A five atom spacer group was incorporated between the bulky calixarene core and the acrylate moiety in order to minimize steric interactions which proved to impede the polymerization. The complexation studies were made by using liquid-liquid and solid-liquid extraction procedures. It has been deduced from the observations that the precursor 5 (5,7,11,23-tetra-tert-butyl-25-hydroxy-27-methoxycalix [4]arene-crown-4) is selective for Hg2+, whereas the polymers are not selective but better extractants for all used metal cations. The extraction data support the conformational change of the calix[4]crown from cone to the other various conformations of calixarene moiety. (C) 2001 Elsevier Science B.V. All rights reserved.