Font Size: a A A

Synthesis, Characterization And Luminescent Properties Of Novel Soluble Polyimide Containing Fluorescent Dye In The Backbone

Posted on:2004-08-15Degree:DoctorType:Dissertation
Country:ChinaCandidate:S G XuFull Text:PDF
GTID:1101360092481175Subject:Polymer Chemistry and Physics
Abstract/Summary:PDF Full Text Request
Three series of perylene-containing and two series of acridine-containing polyimides, which were named as PFFx, PFBx, OPFFx, AFFx and AFBx, respectively, were designed and synthesized. These polyimides were synthesized by a one-step condensation polymerization in m-cresol with isoquinoline as catalyst at 200 C and purged with argon flow. For perylene-containing polyimides, PFFx and PFBx (x = mol-% of PTCDA among the total added dianhydrides) were ternary copolymers, OPFFx (x= mol-% of oxadiazole-containing diamine among the total added diamines) was a quaternary copolymer. For acridine-containing polyimides, AFFx and AFBx (x = mol-% of acridine-containing diamine among the total added diamines) were ternary copolymers. By means of Ft-IR, element analysis, 1H NMR, 13C NMR and GPC (or viscosity), the successful synthesis and imidization of these polyimides were confirmed.The novel polyimide containing fluorescent dye would combine the excellent characteristics of polyimide with the high fluorescent efficiency of dye. The Cardo diamine, 4,4'-(9H-fluoren-9-ylidene) bisphenylamine (FBPA) was used to synthesize polyimide with Cardo structure. The Cardo structure could increase the solubility and thermal stability of the resultant polyimide. Another advantage of Cardo structure was the bulky side groups could inhibit the packing of chains, which would eliminate the inter-chain quenching effects of chromophore groups. To circumvent self-quenching of fluorescent dye at high concentration, a second dianhydride (or diamine) was introduced into the backbone to control the fluorescent dye content in the polyimide. To avoid cross-linking of conjugated chromophore at high temperature, condensed nuclear fluorescent dyes (such as perylene and acridine) were used.Because of the existence of bulky diphenylfluorene units in the backbone, the polyimides exhibited good solubility in common solvents such as chloroform, tetrahydrofuran (THF) or tetrachloroethane (TCE), etc. Their thin films could be prepared by directly spin coating their chloroform (or TCE) solution onto ITO-coated glass or quartz glass. The thermal stability of these polyimides was evaluated by means of TGA and DSC. No apparent glass transition temperature (Tg) was observed up to 350 C, and 10 wt.-% weight loss above the temperature of 540 C. The annealing experiments indicated both perylenediimide groups and acridinediimide groups had high fluorescent thermal stability.Although the solution photoluminescence (PL) spectra of PFFx series (or PFBx series) with different perylene contents were similar to each other, their PL spectra of thin films on quartz were quite different. The peak shapes of PL spectra with low perylene content (PFFl, 0.38 wt.-%; PFBl, 0.46 wt.-%) were almost same as that of their solution PL spectra, which indicated they had the same chromophore groups (singlet perylenediimide groups). But the PL spectra of PFFx (or PFBx) films with high perylene contents were quite different from their PL spectra in solution. Because UV-vis absorption spectra of PFFx and PFBx films indicated that no dimer or other high aggregates existed, their emission spectra in films also originated from perylenediimide monomers. For PFF20 (6.05 wt.-%) and PFB20 (6.09 wt.-%) films, the emission of perylenediimide exciplex mainly constituted their PL spectra. While for other polyimides with perylene content between PFFl (PFBl) and PFF20 (PFB20), the emission of singlet excited states and exciplex of perylenediimide groups overlapped together to constitute their PL spectra. The fluorescene quantum efficiency of PFFx (PFBx) was measured in chloroform solution by using Dhe-PTCDI as reference. For PFFl it was 96.3%, while for PFF20 it was 59.4%.If perylene- and fluorene-containing polyimides were irradiated by 308 nm UV light (the maximum absorption of fluorene moieties, and perylenediimide groups showed no absorption at this wavelength), the emission of fluorene moieties was partly or completely quenched by perylene moieties and the emission of perylene moieties was...
Keywords/Search Tags:fluorescent dye, polyimide, synthesis and characterization, photoluminescence and electroluminescence
PDF Full Text Request
Related items