Birefringence, broadband dielectric and dynamic mechanical relaxation measurements are reported on fibrous cellulose acetate (CTA) plasticized with dibutylphthalate (DBP). Marked differences in physical properties are attributed to retention of nano-structure. Dielectric and mechanical relaxation data show two relaxation processes. The lowest temperature process is attributed to segmental type motion of the polymer chain and the higher temperature process to side-chain/plasticizer relaxation. The plasticization behavior is very different from that observed with other materials. The high-temperature relaxations are consistent with relative sliding of the polymer chain or nano crystallites past one another as in a liquid crystalline material.