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Free volume, mobility, and structural relaxations in poly(ethylene oxide)/poly(methyl methacrylate) blends
Author(s) -
Wästlund C.,
Schmidt M.,
Schantz S.,
Maurer F. H. J.
Publication year - 1998
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.10299
Subject(s) - materials science , differential scanning calorimetry , glass transition , ethylene oxide , amorphous solid , spinodal decomposition , volume (thermodynamics) , crystallization , methyl methacrylate , poly(methyl methacrylate) , oxide , relaxation (psychology) , polymer chemistry , spinodal , chemical engineering , phase (matter) , polymer , analytical chemistry (journal) , thermodynamics , composite material , copolymer , crystallography , organic chemistry , chemistry , psychology , physics , engineering , social psychology , metallurgy
Abstract Time‐dependent structural relaxations in a melt‐mixed 38/62 vol% poly(ethylene oxide)/ atactic poly(methyl methacrylate) blend were studied using several techniques: differential scanning calorimetry, pressure‐volume‐temperature analysis, positron annihilation lifetime spectroscopy, dynamic mechanical analysis, and solid‐state nuclear magnetic resonance. The internal volume (free volume hole size) and the external volume (specific volume) of the blend are found to decrease with aging time. The time scale of the volume changes is the same, suggesting that internal and external volumes can be calculated from each other. Increasing mobility of poly(ethylene oxide), composition fluctuations, and shifting glass transition temperatures are observed upon aging. Phase separation in terms of spinodal decomposition below an upper critical solution temperature occurs within minutes and results in two amorphous phases of different composition. Subsequent crystallization then causes further structural changes.