Studies on amylose and its derivatives. Part II. Light‐scattering and viscosity studies on amylose acetate in dilute solution

Amylose acetate has been fractionated and the solution properties of the fractions studied in two solvents. Weight‐average molecular weights have been determined in nitromethane by the light‐scattering method, and measurements of viscosity as a function of shear stress have been made in chloroform and nitromethane. The Ree‐Eyring flow theory has been used to describe non‐Newtonian behavior which was detected in samples with [η] > 2.0. The parameters in the Mark‐Houwink equation are [η] = 1.10 × 10−5M̄0.87 in CH3NO2 and [η] = 1.06 × 10−5M̄0.92 in CHCl3. The Kratky‐Porod chain model has been found to be most useful in describing the hydrodynamic behavior and indicated that the molecule is much stiffer than the vinyl polymers but more flexible than the cellulose derivatives. The existence of a helical form has been discussed, and it is thought probable that this is the basic form in solution.