Surface activity of aqueous solutions of cellulose acetate with low degree of substitution

Surface activity of aqueous solutions of cellulose acetate (CA) with total degree of substitution (〈 F 〉) ranging from 0.58 to 0.80 was examined. Critical micelle concentration (CMC) of the aqueous CA solutions, determined from the polymer concentration dependence of surface tension (γ), is unequivocally determined by 〈 F 〉, and an increase in 〈 F 〉 of CA brings about a lowering of the CMC. From light scattering measurements on aqueous solutions of CA with 〈 F 〉 = 0.8 at 20°C, it was revealed that in the vicinity of the CMC the micelles in the solution consist of c . four CA molecules, which is very close to the value obtained by analysing the data obtained from the mass action model. The surface tension of aqueous solutions of CA (〈 F 〉 = 0.8) in the polymer concentration range above the CMC was c. 0.74 times that of pure water over the temperature range 0–80°C.