Non‐covalent chemical modification of crown ether side‐chain polymethacrylates with a secondary ammonium salt: a family of new polypseudorotaxanes

Abstract

Here we report syntheses of copolymeric polymethacrylates (5) bearing dibenzo-24-crown-8 (DB24C8) moieties and their non-covalent chemical modification with dibenzylammonium hexafluorophosphate (7) to form side-chain polypseudorotaxanes. The complexation process, primarily driven by hydrogen bonding and π-stacking interactions, was investigated in solution with 1H NMR spectroscopy. By the use of Scatchard and Hill plots it was shown that this system is anticooperative, with a Hill coefficient, nH ≈ 0.45; that is, in addition to the usual entropic effects associated with multiple binding sites, the addition of subsequent ligands to an already complexed macromolecule is retarded. Thus, the more crown moieties per macromolecule or the higher the fraction of complexed sites, the lower the effective macroscopic binding or association constant. Films of the side-chain polypseudorotaxanes showed significant increases in Tg compared to the parent polymers. The effects of pseudorotaxane formation on surface morphology of films are also reported.