Synthesis, Characterization And Emission Properties Of Supramolecular Hyperbranched Polymers By Acid-Base Reaction

Supramolecular chemistry is being widely studied with the aim of developing sophisticated chemical systems from small building blocks by molecular recognition, self-replication, and self-organizatio based on noncovalent interactions. Supramolecular polymer chemistry originated from a close integration of polymer science and supramolecular chemistry, and now stands as a popular and independent research area. In contrast to conventional polymers, the connection between monomers of supramolecular polymers is noncovalent. The dynamic nature of noncovalent interactions gives supramolecular polymers many novel properties, which can be complementary to conventional polymers. In the past decade, chemists elegantly fabricated a large variety of supramolecular polymers. However, almost all of these polymers are one-dimensional. Hyperbranched polymers, three-dimensional polymers prepared from polycondensations of ABm (m≥2) monomers, have potential applications as processing modifiers, toughening additives, drug delivery vehicles, synthesis supporting materials, advanced coatings, polymeric electrolytes, and optical waveguide materials. Here, we report the formation of supramolecular hyperbranched polymers from self-organization of AB2monomers containing complementary recognition sites, a dibenzo[24]crown-8(DB24C8) ring and two secondary amine centers. We have further studied the application of these improved systems in prepairing more complicated superamolecular systems such as supramolecular hyperbranched polymers.The content of this dissertation includes the following four parts:1. The recent advances of the studies in the supramolecular polymers have been reviewed. The design principle and mechanism of supramoleclar chemistry and a few examples for supramolecular polymers were introduced. 2. A π-conjugated AB2monomer1with a dibenzo[24]crown-8(DB24C8) ring and two secondary amine centers has been synthesized. Upon treating its dichloromethane solution with trifluoroacetic acid (TFA) for protonation of the amine groups, the resulting dialkylammonium ion centers are encircled by the DB24C8groups, leading to the formation of a supramolecular hyperbranched polymer, TFA-1with rather strong π-π stacking interactions between the conjugated cores. The SHP can be completely depolymerized by adding slightly excessive N-tert-butyl-N’,N’,N’",N",N’",N’"-hexamethylphosphorimidic triamide. The acid-base controlled process induces a reversible change for the fluorescence intensities of the solutions due to the controllable presence of the π-π stacking interactions between the conjugated cores. This dynamic behavior is significant with respect to "smart" supramolecular polymer materials.3. The SHP TFA-1also can be completely depolymerized by adding slightly excessive tetrabutylammonium fluoride, or tetrabutylammonium acetate. The ion-pair controlled process induces a reversible change for the fluorescence intensities of the solutions due to the controllable presence of the π-π stacking interactions between the conjugated cores.4. A luminescence supramolecular hyperbranched polymer is reversibly fabricated by successively adding acid and base to a solution of an AB2platinum(Ⅱ) monomer C1in dichloromethane on the basis of acid-base controllable host-guest recognition of dibenzo[24]crown-8moieties with dialkylammonium ion centers. The acid-base switching by properties of both the monomer and polymer have been studied in solution, using1H NMR spectra, UV/vis absorption spectra, luminescence spectra and dynamic light-scattering analysis. The experimental results demonstrate that the functionalized organometallic Pt-AB2monomer Cl, along with their polymeric derivatives, undergo quantitative, efficient, and reversible switching processes in solution.