Studies Of Crown Ether-based Supramolecular Polymers And Pillararene-based Polypseudorotaxanes

The low molecular weight monomers and traditional covalent polymer-based macromonomers, which contain some certain molecular recognition groups can self-assembly into supramolecular polymers. Supramolecular polymers, which combine the properties of traditional polymers and reversible and stimuli-responsive characteristics of supramolecular nocovalent bonds, are very important candidates for the development of smart materials. In this dissertation, on the one hand, we focus on the preparation and applications of supramolecular polymers constructed from low molecular weight monomers and macromonomers via the crown ether-based recognition motifs. On the other hand, study on polypseudorotaxanes constructed from pillararene and a variety of traditional polymers and their self-assembly properties was also conducted.In the first part, a microsphere pattern and highly ordered supramolecular polymer honeycomb-patterned films were fabricated successfully via the static breath figure method. The supramolecular polymer that was used to prepare these intriguing films was obtained from the self-organization of a heteroditopic monomer based on the benzo-21-crown-7/secondary ammonium salt recognition motif. The solvents and monomer concentration played an important role in the fabrication of these supramolecular polymer microstructures. A highly-ordered honeycomb-patterned film was obtained via the static breath figure method using acetonitrile as the solvent at a concentration of30wt%.In the second part, based on the benzo-21-crown-7(B21C7)/secondary ammonium salt molecular recognition motif, dual-responsive supramolecular chain extended polymers with a biodegradable poly(ε-caprolactone)(PCL) chain as the scaffold were successfully prepared by self-assembly of a heteroditopic macromonomer which was synthesized by a combination of ring-opening polymerization and click reaction. Due to the enviromental responsiveness of the recognition of the B21C7host unit to the secondary ammonium salt guest moiety, the supramolecular chain extended polymers respond to pH and cation stimuli. The crystallization behavior of the PCL segments of the supramolecular chain extended polymer and its neutral counterpart were investigated by polarized optical microscopy. The B21C7/secondary ammonium salt host-guest interactions cause a decrease of the chain mobility of PCL and make the crystallization rate of PCL much slower in comparison with the case for its neutral counterpart. From this supramolecular chain extended polymer, nanofibers were obtained successfully via electrospinning.In the third part, three polymers PEG-DBAS, DB24C8-PCL-B21C7and PS-DAAS based on crown ether recognition motif were successfully prepared by the combination of atom transfer radical polymerization (ATRP), ring open polymerization (ROP) and efficient click reaction. AB, BC and ABC supramolecular block polymers have supposed to be constructed from the self-assembly of the three polymers.’H NMR experiments indicated that crown ether-based host-guest interactions were too weak to form supramolecular block polymers. How to build a crown ether-based ABC-type supramolecular block polymer efficiently need to be further studied.In the forth part, we successfully synthesized a series of new polypseudorotaxanes from DEpillar[5]arene and polyethylene-based polymers.1H NMR experiments indicated that pseudopolyrotaxane can be successfully constructed from DEpillar[5]arene and n-C36H74, and there are6carbon atoms (3ethylene units) contained in the cavity of DEpillar[5]arene. Pseudopolyrotaxane also successfully constructed from DEpillar[5]arene and polymethylene (PM66-OH) and polymethylene-block-polycaprolactone(PM66-b-PCL102).Polypseudorotaxanes based on block-selected inclusion complexation between DEpillar[5]arene and polyethylene-block-poly(ethylene glycol)(PE-b-PEG1400and PE-b-PEG2250) were also successfully constructed. WAXD showed that in the solid state, the polypseudorotaxane was completely different from PE-b-PEG, DEpillar[5]arene and their solid mixture. TGA analysis showed that these polypseudorotaxane are more thermally stable than free PE-b-PEG and solid mixture of PE-b-PEG and DEpillar[5]arene.In the fifth part, polypseudorotaxanes were successfully constructed from DEpillar[5]arene and three type of PCL-based polymers (L-PCL, S-PCL, PEG-b-PCL). The polypseudorotaxanes were in detail characterized by1H NMR and FT-IR experiments. The self-assembly of DEpillar[5]arene, PEG-b-PCL and pseudopolyrotaxane were also studied. The microstructures of pseudopolyrotaxanes are completely different from PEG-b-PCL and DEpillar[5]arene.