A modified polystyrene, poly(styrene-co-p-(hexafluoro-2-hydroxy-2-propyl)styrene)(FPS), was blended with syndiotactic or isotactic poly(methyl methacrylate) (PMMA) in toluene. Films were prepared under different conditions to control the self-aggregation of PMMA segments. The formation of hydrogen bonding and the attendant changes in the aggregation or crystallization of PMMA segments were determined in the solid state by means of FTIR and WAXD. The results indicate that the aggregation of the PMMA segments is diminished by hydrogen-bonding interaction in both s-PMMA and i-PMMA blends. However, hydrogen bonding between the hydroxyl and carbonyl groups is slightly favored in the s-PMMA blends.