C-13 NMR-STUDIES OF THE THERMAL-BEHAVIOR OF AQUEOUS-SOLUTIONS OF CELLULOSE ETHERS

Solution state n.m.r. techniques have been used to study 10% w/v aqueous solutions of methylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose. C-13 n.m.r. spectra taken at temperatures from ambient to 70-degrees-C show loss of peak intensities of both backbone and substituent signals due to liquid/solid phase separation processes at high temperatures. The substituents on methylcellulose become immobile and those on hydroxypropylcellulose retain mobility. This information is interpreted on the basis of the different structures of the solid phases and the thermodynamics of the phase separation process.