We describe optical diffraction, or 2D angle-resolved light scattering, measurements for probing structure and morphological dynamics of isolated poly(ethylene glycol) (PEG) microparticles doped with NaCl or CaCl2. Of specific interest was the effect of dopant salt concentration and polymer host molecular weight on composite microparticle homogeneity (phase-separation behavior) and evaporation dynamics determined from changes in both microparticle size and refractive index with time. In general the drying rate was higher for microparticles doped with CaCl2, and only in the case of CaCl2 doped microparticles was PEG molecular weight found to effect the drying rate. Furthermore, CaCl2 doped microparticles had a higher concentration threshold with regard to homogeneity when compared with NaCl doped microparticles. The results are discussed in terms of the known structures for monovalent electrolytes doped into PEG thin films and polymer-like oligomers in the gas phase, and on possible modifications of these structures due to differences in the intermolecular interactions of the two cationic species with the residual solvent and the polymer matrix.