AbstractThe electric dipole moments (per repeating unit) of cellulose acetate and tricarbanilate, and amylose acetate and tricarbanilate were determined in 1,4‐dioxane solution at 30°C. The parallel component of the moment to the chain contour was also estimated for samples of various molecular weights, and they were almost independent on molecular weight, indicating no excluded volume effect on the dipole moment. The persistence dipole moment, and monomer dipole component along the chain contour for cellulose derivatives were about 50% smaller than those for amylose derivatives. The relation between the dipole moment and the chain dimension is discussed for cellulose‐ and amylose derivat