Coherence of thermal transitions in poly(N-vinyl pyrrolidone)-poly(ethylene glycol) compatible blends 2. The temperature of maximum cold crystallization rate versus

Differential scanning calorimeteric (DSC) heating thermograms of amorphous poly(N-vinyl pyrollidone) (PVP) blends with short-chain poly(ethylene glyco l) (PEG) feature exotherms of cold crystallization coupled with symmetric m elting endotherms, which relate to the state of the crystalline component, PEG, while PVP-PEG hydrogen-bonded complex reveals itself as an amorphous p hase. As PEG content in blends exceeds a characteristic level, PEG cold cry stallization occurs upon heating of the coal-quenched samples through their glass transition temperatures (T-g). The contributions of both thermodynam ic and kinetic factors to the occurrence of non-crystallizable PEG have bee n analysed by considering the dependence of the PEG cold crystallization te mperature, T-c, on blend T-g and composition along with the compositional d ependence of the heat of melting of PEG. The stoichiometry of the PVP-PEG H -complex was evaluated from DSC thermograms as the amount of non-crystalliz able PEG in PVP-underloaded blends. (C) 2000 Elsevier Science Ltd. All righ ts reserved.