Cellulose and its derivatives are biodegradable and renewable. Cellulose acetates (CA) are the most important derivatives, due to their wide range of potential applications in textiles, food, engineering materials and pharmaceutical industries, but are difficult to process due to their high melting temperature, close to decomposition. Thus plasticizers must be used for CDA processing. Extensive research has been dedicated to identify efficient plasticizers. There are fundamental issues as well. CDA-plasticizer mixtures are usually partially miscible. Miscibility is governed by hydrogen bonding. A complex interplay between the kinetics of phase separation and freezing down of the motions on approaching Tg takes place. The objective of the proposed SANS experiment is to study the non-equilibrium morphologies of these systems, which result from the interplay between phase separation kinetics and glass transition taking place during solvent casting. With SANS, we expect to be able to characterize the amplitude and typical length scale of concentration fluctuations, as a function of the process (kinetics of solvent evaporation, temperature).