Rotational Behavior of N-(2-Naphthylmethyl)carbazole in a 1,2-Dichloroethane/Poly(ethylene oxide) Mixture Measured by a Time-Resolved Fluorescence Depolarization Method

Abstract

Abstract Stationary and nanosecond time-resolved fluorescence depolarization spectroscopy has been used to detect the rotational behavior of N-(2-naphthylmethyl)carbazole as a function of the solvent viscosity. The variation in the viscosity was effected by the addition of poly(ethylene oxide), and the range of the variation was 0.78 N m−2 s−1 to 33 × 10−3 N m−2 s−1. The viscosity dependence of the rotational diffusion coefficient (Dr) in the high-viscosity region was different from that in the low viscosity region. Radii of gyration of N-(2-naphtylmethyl)carbazole in the low and high viscosity regions were about 8 and 4 Å, respectively. The former agrees with the total size of N-(2-naphthylmethyl)carbazole, and the latter with the size of the cabazolyl group. The crossover point of the rotational motion of N-(2-naphthylmethyl)carbazole was at a concentration of 0.6 g ml−1 of poly(ethylene oxide), which coincided with the overlap concentration of poly(ethylene oxide) molecules. Therefore, the rotational mode of N-(2-naphthylmethyl)carbazole varies from the whole to the carbazolyl group by the addition of poly(ethylene oxide).