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

Were we report syntheses of copolymeric polymethacrylates (5) bearing diben zo-4-crown-8 (DB24C8) moieties and their non-covalent chemical modification with dibenzylammonium hexafluorophosphate (7) to form side-chain polypslud orotaxanes. The complexation process, primarily driven by hydrogen bonding and pi-stacking interactions, was investigated in solution with H-1 NMR spe ctroscopy. By the use of Scatchard and Hill plots it was shown that this sy stem is anticooperative, with a Hill coefficient, n(H) = 0.35; that is, in addition to the usual entropic effects associated with multiple binding sit es, the addition of subsequent ligands to an already complexed macromolecul e is retarded. Thus, the more crown moieties per macromolecule or the highe r the fraction of complexed sites. the lower the effective macroscopic bind ing or association constant, Films of the sidechain polypseudorotaxanes sho wed significant increases in T-g compared to the parent polymers. The effec ts of pseudorotaxane formation on surface morphology of films are also repo rted.