Studies on cellulose derivatives. Part III. Unperturbed dimensions of hydroxyethyl cellulose and other derivatives in aqueous solvents

Abstract

AbstractValues of K for the equation [η]θ = K Z̄ have been calculated for hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, sodium carboxymethyl cellulose and cellulose using the treatment of KURATA and STOCKMAYER.Expansion factors, αη were calculated from the K‐values for hydroxyethyl cellulose in water and cadoxen. In these solvents the measured molecular dimensions differ greatly, but application of the corresponding αη‐values leads to the same unperturbed dimensions. In contrast, different unperturbed dimensions result when employing expansion factors calculated from second virial coefficients.The origin of dln[η]/dT in water solution is discussed.It appears that increasing the monomer molecular weight in cellulose derivatives initially results in decreased unperturbed molecular extensions; the steric effect ultimately predominates when very large substituents are introduced. For the polyelectrolyte sodium carboxymethyl cellulose the unperturbed extension increases markedly with increasing substitution.From the magnitudes of (R/R)½ and the persistence lengths calculated from the K‐values, it is concluded that cellulose and these derivatives may be considered as normal, flexible polymers in the unperturbed state.