ELECTRICALLY CONDUCTING DENDRIMERS

Generations 1-5 of poly(amidoamine) (PAMAM) dendrimers were peripheral ly modified with cationically substituted naphthalene diimides. Reduct ion with sodium dithionite in water or formamide formed anion radicals on the diimide moieties. Evaporation of water under argon produced po wders of the reduced dendrimers that were electrically. conductive. Us ing formamide as solvent, films were cast of reduced generation-3 modi fied dendrimers. Fully reduced films (1.1 e/diimide) gave conductiviti es under ambient conditions of about 10(-3) S/cm. Films formed from th ese dendrimers that were half-reduced (0.55 e/diimide) gave a 10(-2) S /cm. Near-infrared (NIR) spectra on the films showed the formation of pi-stacks with maximum absorbance beyond 2000 nm. The wavelength and i ntensity of this absorbance correlated with the conductivity. The cond uctivity increased with increased humidity above the films reaching va lues as high as 18 S/cm at 90% relative humidity. The conductivity was in all cases electronic and isotropic. The conductivity-humidity effe ct was probed by NIR spectroscopy, X-ray powder diffraction, and quart z crystal microbalance measurements. These studies suggest that the am orphous films absorb water from the air and at high;humidity they are plasticized, allowing faster stack-to-stack electron hopping and incre ased conductivity.