HYDROXYPROPYL METHYL CELLULOSE ACETATE SUCCINATE

solubility :: Practically insoluble in ethanol (95%), hexane, unbuffered water, and xylene. On the addition of acetone, or a mixture of ethanol (95%) and dichloromethane (1 : 1), a clear or turbid viscous solution is produced. Hypromellose acetate succinate also forms a clear or turbid solution in buffers of pH greater than 4.5 with the rank order of solubility for the various grades increasing with the ratio of acetyl over succinoyl substitution. The exact pH value at which the polymer starts to swell and dissolve depends on the buffer type and ionic strength, although the rank order for the different grades is independent of the buffer used. No solvent has been found to completely dissolve hypromellose acetate succinate polymer; the resulting clear or turbid solutions significantly scatter light in both static and dynamic light scattering experiments, indicating that the polymer may exist as colloids or aggregates. The data is collated from the Shin-Etsu Chemical Co. Ltd and the research work of the authors (R Chen, BC Hancock, and RM Shanker).