Experiments were performed to determine how the supercritical antisolvent (SAS) precipitation process is affected by the miscibility of the solute in the solvent. Polymers and copolymers from the monomers methyl methacrylate and vinyl pyrrolidone were processed through SAS to observe the effects of their solubility in ethanol on the SAS spray characteristics and the resulting particles. The solubilities of the copolymers were influenced by varying the methyl methacrylate to vinyl pyrrolidone ratio, which reduces the solubility in ethanol. A high-resolution imaging system was used to study the spray characteristics of the polymer/ethanol solutions in the SAS precipitation process. The resulting particles were then characterized using a scanning electron microscope. Cloud point experiments and FTIR were used to evaluate the saturation concentration in ethanol and monomer ratio of each copolymer. Process visualizations revealed that the spray of each polymer or copolymer solution into carbon dioxide had similar jet breakup lengths and droplet diameter distributions, and that these spray characteristics appear to be closely associated with the solvent (ethanol) properties. The SEM images showed the change in particle characteristics relative to the solubility of the polymer or copolymer in ethanol.