Synthesis and properties of copolymers containing cucurbit[6]uril-based pseudorotaxane structure

Abstract

Novel copolymers based on acrylamide (AM) and complex pseudorotaxane monomer N′-(3-vinylbenzyl)-1,4-diaminobutane dihydrochloride with cucurbit[6]uril (CB[6]) (3VBCB) were prepared via free-radical polymerization in aqueous solution, and characterized by 1H-NMR, FT-IR, elemental analysis and static light scattering. The compositions of the copolymers (PAM3VBCB) with pseudorotaxane units were determined by 1H-NMR and elemental analysis. Thermal properties of the copolymers were studied by TGA, and the effects of the copolymer concentration and pH on the average hydrodynamic radius (R h) of the copolymer molecules were studied by dynamic light scattering (DLS). The experiment data show that CB[6] beads are localized on 1,4-diaminobutane units in side chains of the copolymers. TGA results show that thermal stability of the copolymer increases with increasing the content of pseudorotaxane unit because of the enhanced rigidity and the bulky steric hindrance of 3VBCB in side chains of PAM3VBCB. DLS data show that the average hydrodynamic radius of copolymer molecules increases with the increase in the copolymer concentration, and both the pH and electrical conductivity of PAM3VBCB solutions demonstrate an acute change with addition of NaOH because of CB[6] dethreading from the side chains of PAM3VBCB. CB[6] threading and dethreading of PAM3VBCB could be controlled by addition of BaCl2 and Na2SO4.