Polymer domain sizes are related to many of the physical properties of polymers. Here we present a solid-
state NMR experiment that is capable of measuring domain sizes in multi-component mixtures. The
method combines selective excitation of carbon magnetization to isolate a specific component with pro-
ton spin diffusion to report on domain size. We demonstrate the method in the context of controlled
release formulations, which represents one of today’s challenges in pharmaceutical science. We show
that we can measure domain sizes of interest in the different components of industrial pharmaceutical
formulations at natural