Synthesis And Optical Properties Of Anthracene-Based Polymers And Oligomers

In this paper, we demonstrate the synthesis and enhanced two-photon absorption (TPA) properties of two novel tetradonor-containing anthracene-centered cross-conjugated polymers with 2,6-diarylenevinylene/9,10-diaryleneethynylene motif,poly[(9,10-bis(p-didecylaminophenylethynyl)-2,6-anthracenevinylene)-alt-(N-octyl-3,6-/2,7-carbazolevinylene)] (P1/P2). P1 and P2 are synthesized by means of Wittig-Horner coupling of 2,6-Bis(diethylphosphorylmethyl)-9,10-di(p-N,N-didecyl- amino-phenyleneethynyl)-anthracene with N-Octyl-3,6/2,7-diformylcarbazole. They have the number-average molecular weights of 1.82×10~4 and 2.15×10~4 g/mol, respectively, and are readily soluble in common organic solvents and emit strong orange one- and two-photon excitation fluorescence with the peaks around 555 nm. The maximal TPA cross sections (δ) of P1 and P2 in toluene measured by the two-photon-induced fluorescence method are 2360 and 1520 Gm per repeating unit, respectively. Theseδvalues are significantly larger than the sum of that of the two corresponding linear analogues, indicating that the cooperatively enhancedδhas been achieved in the anthracene-centered cross-conjugated polymers, which are different from the reported characteristics of benzene- and pyrazine-centered cross-conjugated chromophores showing no enhancement ofδ. These results underline that anthracene ring is a promising crossπ-center and can be used to construct novel cross-conjugated polymers exhibiting distinctive optoelectronic properties.In the process of preparing the linear analogues of anthracene-centered cross-conjugated polymers, we found that the optical properties and aggregation behavior of 9,10-DSA with different length alkyl side chain is different. For all compounds concerned, the wavelength of main peak in the one-photon absorption spectra is 435nm, and peak wavelength of the one-photon fluorescence spectra is 557nm using THF as the eluent. But red-shifted (95-151nm) was clearly obvioused in the solid state, there is no relationship between the length of alkyl side chain and the degree of red-shift. Fluorescence intensity increase with the increasing of water content through fluorescence emission (PL) spectra of compounds, this is means that all compounds have the property of AIE (Aggregation-Induced Emission). It can be seen from the DSC trace that with the growth of alkyl chains, the melting point decreases. Amplified spontaneous emission (ASE) with low threshold value indicates that the C1 and C7 crystals with uniaxially oriented molecules are very suitable materials for the organic solid-state laser diodes.