Oscillatory shear rheometry data for a miscible blend of 20 wt % poly(vinylidene fluoride) (PVDF) in poly(methyl methacrylate) (PMMA) shows breakdown of time-temperature superposition for this blend. A comparison between glass transition temperature which PMMA chains sense in the blend and effective glass transition temperature of this component indicates that, the Lodge-McLeish model can describe terminal dynamics of PMMA. In addition, terminal dynamics of PVDF chains in the blend is similar to that of its pure state in agreement with the mentioned model. At segmental level, dynamic mechanical thermal analysis of four wholly amorphous blends suggests that cooperativity of molecular motions decreases upon addition of 30 and 40 wt % PVDF to PMMA. This behavior has been confirmed via calculation of degree of fragility which presumably is attributed to strong tendency of PVDF chains to self-association rather than inter-association with PMMA chains according to the FTIR results. (c) 2007 Wiley Periodicals, Inc.