Synthesis, characterization and properties of side-chain pseudopolyrotaxanes consisting of cucurbituril[6] and poly-N1-(4-vinylbenzyl)-1,4-diaminobutane dihydrochloride

Pseudopolyrotaxanes 3 is synthesized from cucurbituril[6] (CB[6]) and polymer 2 (poly-N1-(4-vinylbenzyl)-1,4-diaminobutane dihydrochloride) in water by simple stirring at room temperature. The monomer 1, polymer 2 and pseudopolyrotaxanes 3 are characterized by 1H NMR, 13C NMR, FT-IR and elemental analysis. In 3, the CB[6] beads are localized on tetramethylene units in side chains of 2, and combine N+ by noncovalent bonds. The degree of threading (number of CB[6] beads per repeat unit) can be controlled from 0 to 1.0 by controlling the amount of CB[6] added. The properties of polymer 2 and pseudopolyrotaxanes 3 are researched by TGA, X-ray powder diffraction (XRD), environment scanning electron microscope (ESEM) and potentiometric titrations. The pseudopolyrotaxanes have higher thermal stability and chain regularity than the parent polymer which are attributed to the bulkiness and the rigidity of the CB[6] threaded. The decomposition temperature and chain regularity of the pseudopolyrotaxanes increase with increasing amount of CB[6] threaded. The effects of salts (NaCl, NaBr or NaI) to pseudopolyrotaxanes are studied by the transmittance with UV–vis, and the results show that NaI is the satisfied precipitant to the pseudopolyrotaxanes. The surface morphologies of pseudopolyrotaxanes 3 observed by ESEM shows a series of spherical particle with different diameter. The results of potentiometric titrations show that the pseudopolyrotaxanes 3 have larger pKav and smaller n than polymer 2.