To better understand the physical properties of multi-component polymers it is important to elucidate the phase mor-phology notably by determining the degree of crystallinity and the domain sizes in the mixture. Specifically for EC/HPC film coatings in controlled release formulations, the drug release behavior is governed primarily by the phase structure of the water-soluble
phase (HPC) [4]. This structure is defined by the number of domains, their size and their connectivity [5,6] within the insoluble EC matrix. Once the formulation enters the gastrointestinal tract,