Free Volume Determination in Polymers and Polymer Blends

摘要: The free volume of a polymer, which corresponds to the unoccupied regions accessible segmental motions, is an important parameter for understanding and predicting many its characteristic properties. concept basis molecular mobility in polymers. A non-destructive technique that can be used obtain parameters polymers positron annihilation lifetime spectroscopy (PALS). aim present work was explore possibilities limitations using PALS studies polymer blends. Chemical physical influences on measured were studied homopolymers, copolymers possibility extracting hole size distributions from spectra investigated. An inter-laboratory comparison positronium lifetimes intensities with showed ortho-positronium reproduced well under large variety experimental conditions. These two essentially contain information. It shown extracted by applying maximum entropy principle. Experimentally obtained compared theoretically calculated simulations. considerable fraction small holes not ortho-positronium. affected chemical constitution polymer. Copolymers styrene maleic anhydride acrylonitrile found inhibit formation. inhibition strongly dependent amount polar constituents are part main chain. Large variations average blends poly(ethylene oxide) poly(methyl methacrylate) as function composition. Moreover, time temperature-dependent, behavior attributed phase separation crystallization Investigations miscible immiscible styrene-maleic styrene-acrylonitrile show measurements promising miscibility