Different hydroxyl content poly(styrene-co-p-(hexafluoro-2-hydroxylisopropyl)-alpha-methylstyene) [PS(OH)-X] copolymers were synthesized and blends with 2,2,6,6-tetramrthyl-piperdine-1-oxyl end spin-labeled PEO [SLPEO] were prepared. The miscibility behavior of all the blends was predicted by comparing the critical miscible polymer-polymer interaction parameter (X-crit) with the polymer-polymer interaction parameter (X). The micro heterogeneity, chain motion, and hydrogen bonding interaction of the blends were investigated by the ESR spin label method. Two spectral components with different rates of motion were observed in the ESR composite spectra of all the blends, indicating the existence of microheterogeneity at the molecular level. According to the variations of ESR spectral parameters T-a, T-d, DeltaT, T-50G and tau(c), with the increasing hydroxyl content in blends, it was shown that the extent of miscibility was progressively enhanced due to the controllable hydrogen bonding interaction between the hydroxyl in PS(OH) and the ether oxygen in PEO. (C) 2004 Wiley Periodicals, Inc.