Synthesis And Properties Of Functional Chiral Polymers

Chirality is a ubiquitous phenomenon in nature. As the basic unit of life, amino acids and riboses are almost all L- and D-configuration, respectively, breaking the symmetry at the molecular level. These asymmetric molecules are the material basis of life, and optical activity is the basis of orderly and organized life. Circularly polarized luminescence (CPL) is the selective emission of left-and right-handed circularly polarized light originated from chiral chromophore system. Chiral polymer exists in the isolated monomeric state in the solution, while in the form of aggregates in aggregated state. The different existence form of chiral polymer has an influence on its CPL. The chiral unit in chiral polymer can exert influence on the polymer packing and electronic structure, and facilitates the intrachain winding and wrapping, which are in favor of energy transfer.The research in this paper can be divided into two parts:one is the synthesis of the tetraphenylethene-based chiral polymer and the study on its aggregation-induced emission and circularly polarized luminescence properties; the other is the syntheses of the chiral Eu(III)-grafting polymers and the study on their through bond energy transfer and quantum yield regulation.Section 2:The tetraphenylethene (TPE)-based chiral polymer (TPETyr) was synthesized by the polymerization of 1,2-bis(4-ethynylphenyl)-1,2-diphenylethene (M-1) and 3’,5’-diiodo-N-αa-tert-butoxycarbonyl-O-octyl-L-tyrosine methyl ester (M-2) via Sonogashira cross coupling. Interestingly, the generated luminogen emits weak fluorescence in THF solution, but becomes strongly luminescent as nanoparticle suspensions upon addition of water, demonstrating a novel phenomenon of aggregation-induced emission (AIE). The resulting TPETyr can also exhibit large CPL dissymmetry factor (glum) in both solution and aggregate states. More importantly, the glum is environment-dependent and can be tuned in the range of 0.44 to 0.08 by changing the content of water in THF solution.Section 3:Three novel chiral polymers were prepared from the corresponding monomers reacting with (R,R)-1,2-aminocyclohexane via a nucleophilic addition-eli-mination reaction. Eu(TTA)3-2H2O was directly coordinated with the chiral polymers to afford the corresponding Eu(III)-grafting polymers (P-2, P-4 and P-6). Spectral analysis reveals that the energy transfer mode in the chiral Eu(III)-grafting polymers is through bond energy transfer (TBET), that is, energy thransfers from the excited state of the chiral polymer backbone to the Eu(III) ion center through covalent bond. Large Stokes shifts (△λmax=265 nm) and fluorescence emission shifts (△λmax=214 nm) can also be observed. Moreover, the quantum yields of the Eu(III)-grafting polymers (P-2, P-4 and P-6) are 60 to 100-fold higher than that of Model and can be tuned by the number of the methylene unit in the Eu(III)-grafting polymer from 3.01% to 5.30%.