The water-induced aggregation behavior of rod-coil diblock copolymers based on poly(ethylene oxide) (PEO) andpoly{(+)-2,5-bis[4'-((S)-2-methylbutoxy)phenyl]styrene} (PMBPS), PEO
104-
b-PMBPS
53, was investigated in thecommon solvent THF and in the selective solvent dioxane. Before adding water, PEO
104-
b-PMBPS
53 stayed as singlepolymer chains no matter what conformation the PEO block took (i.e., either the random coil conformation in THFor the compact globule conformation in dioxane). The critical water content (~6 wt %) at which PEO
104-
b-PMBPS
53began to aggregate was also similar in both solvents, indicating that PMBPS dominated the aggregation process.However, the size, the size distribution, and the morphology of aggregates in THF/water were quite different fromthose in dioxane/water. Narrowly distributed spheres with
Rh 20 nm were observed in dioxane, whereas in THF,a bimodal distribution peaked at 3 and ~300 nm, was observed. The results from 2D wide-angle X-ray diffractionand polarized optical microscopy demonstrated that the PMBPS blocks packed in a parallel pattern upon aggregationin dioxane/water. The anisotropic disclike structures observed in THF/water also indicated the orientation of thePMBPS blocks upon forming aggregates in dilute solution.