Narrow Results

A series of polymers bearing azobenzene and carbazole groups for photorefractive purpose were prepared via post-azo-coupling reaction. The successful reaction was identified by spectroscopic analysis and gel permeation chromatography. This approach is more facile compared with the direct polymerization of corresponding functional monomer. The polymers prepared have weight average molecular weight of higher than 1.5×10⁴ and are easily soluble in common organic solvents like chloroform and tetrahydrofuran, polymer films with high optical quality could be easily fabricated through solution casting. Glass transition temperature (T_g) of the polymers ranges from 60°C to 182°C, depending on the alkylene spacer length between the functional side group and the polymer backbone, and the polymers are relatively stable under 300°C.

New hyperbranched poly(aryleneethynylene)s containing carbazole moieties are synthesized in high yields (up to 87%) by polycyclotrimerization of 3,6-bis(4-ethynylphenyl)-9-octylcarbazole and its copolymerization with 1-octyne catalyzed by CpCo(CO)₂ in THF. The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, UV, photoluminescence, and cyclic voltammetry analyses. All the polymers are soluble in common organic solvents and show outstanding thermal stability (≥ 430°C). They graphitize in high yields (up to 79%) when pyrolyzed at 800°C. Upon photoexcitation, the polymers emit a strong deep blue light of ca. 400 nm with quantum yields larger than 60%.

A new luminescent and thermally stable platinum(II) polyyne polymer trans-[–Pt(PBu₃)₂C≡CArC≡C–]_n (P1) containing the 2,7-fluorene chromophoric spacer substituted by pendant carbazolyl group via long alkyl bridges. The regiochemical structures of these compounds were studied by various spectroscopic analyses. We report the photophysical properties of this group 10 polymetallayne and a comparison was made to its binuclear model complex trans-[Pt(Ph)(PEt₃)₂C≡CArC≡CPt(Ph)(PEt₃)₂] (M1) as well as to those with non-carbazole-containing fluorene spacer (P2 and M2). Upon photoexcitation, each of P1 and M1 emits an intense purple-blue fluorescence emission in the near-UV to visible region in dilute fluid solutions at room temperature. Harvesting of organic triplet emissions harnessed through the strong heavy-atom effects of platinum metal was examined and at 77 K, each of the metalated compounds displayed dual emission bands, viz. both the fluorescence and the lower-lying phosphorescence. Spectroscopic results revealed that the formation of excimers was suppressed by introducing carbazole side groups. The spatial extent of the lowest singlet and triplet excitons in P1 and M1 was fully elucidated. Such organometallic poly(fluorenyleneethynylene)s anchored with the carbazole pendants was found to have an improved thermal stability and suppressed aggregation.

Novel 9-proparylcarbazole monomers containing amino acid moieties, 2-N-(tert-butoxycarbonyl)-L-alanine-9-proparylcarbazole ester (1), 2-N-(tert-butoxycarbonyl)-L-O-cyclohexyl-L-glutamic acid-9-proparylcarbazole ester (2) and 2-N-(tert-butoxycarbonyl)-L-phenylalanine-9-proparylcarbazole ester (3) were synthesized and polymerized with (nbd)Rh⁺ [η⁶-C₆H₅B^–(C₆H₅)₃] to give the corresponding polymers with number-average molecular weights ranging from 7050 to 10500 in 70%–86% yields. The polymers were completely soluble in toluene, CHCl₃, CH₂Cl₂, THF and DMSO, but insoluble in hexane, diethyl ether and MeOH. The specific rotation studies revealed that poly(1)–poly(3) do not took predominantly one-handed helical structures in the solvents although they possess chiral groups. The polymers emitted fluorescence in 0.40%–2.35% quantum yields. The cyclic voltammograms of the polymers indicated that the polymers exhibited electrochemical properties.