Linear and two-photon photophysical properties of a series of symmetrical diphenylaminofluorenes

A series of linear, symmetrical, diphenylaminofluorene-based materials are reported. The series investigated was model 9,9-didecyl-2,7-bis(N,N-diphenylamino)fluorene (1), oligomer 9,9-didecyl-N,N-bis(9,9-didecyl-7-N,N-diphenylaminofluoren-2-yl)-N,N-diphenyl-fluorene-2,7-diamine (2), and poly(9,9-didecyl-2,7-diphenylaminofluorene) (3). Structural characterization and photophysical properties, including linear absorption, quantum yields, single photon fluorescence, and two-photon absorption (2PA) spectra, were studied in polar and nonpolar solvents. 2PA spectra were determined by two independent methods: a nonlinear transmission method employing a femtosecond white-light continuum (WLC) and a two-photon fluorescence (2PF) method. Polymer 3, a low-molecular-weight polymer with fourteen fluorene units, exhibited a very large two-photon absorption cross-section of 17 200 and 6800 x 10(-50) cm(4) s photon(-1) molecule(-1) as estimated from the WLC and 2PF methods, respectively