Two kinds of nanoscale dynamic heterogeneity in single-phase polymer blends and their common origin

Differential scanning calorimetry (DSC) and laser-interferometric creep rat e spectroscopy (CRS) were used for kinetic and discrete analysis of segment al motion within land close to) glass transition range in polystyrene - pol y(alpha-methyl styrene) (PS/PMS) and polystyrene - poly(vinyl methyl ether) (PS/PVME) miscible blends. Two kinds of segmental dynamics heterogeneity w ere found. Separate 'unfreezing' of PS and PMS segmental motions was observ ed that manifested itself in two Tgs and simultaneous large drop in the Tg s, as well as glass transition activation energy, motional event scale and cooperativity degree values, down to the beta-relaxation parameters. The wi de activation energy dispersion within a single broad glass transition in P S/PVME blends was found, and this relaxation region was subdivided, by CRS, into several predicted kinds of segmental motion. Both results are treated in the framework of the concept of common segmental nature of alpha- and b eta- relaxations in flexible chain polymers.