Low-temperature specific heat capacities of the miscible blends of poly(methyl methacrylate) and poly(vinylidene fluoride)

The specific heats of miscible blends of amorphous poly(methyl methacrylate) (PMMA) and semicrystalline poly(vinylidene fluoride) (PVDF) have been measured between 2.0 and 65K. The behaviour of the specific heat of pure PMMA is consistent with the universal feature expected for a solid in which the topological disorder introduces an excess of low-energy vibrational modes; the peak in C-p/T-3, compared with that revealed in semicrystalline PVDF, is enhanced. The PMMA-PVDF binary blends are wholly amorphous and show heat capacities which below 15K are not dependent on the compositions and equal to that measured in PMMA. These striking observations have been interpreted in terms of a simple linear overlap of the contributions to the specific heat from wholly amorphous PMMA and PVDF, weighted by their proportions.