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Phase transformation on heating of undercooled melt of poly(ethylene oxide)‐urea molecular complex
Author(s) -
Bogdanov Bogdan,
Michailov Marin,
Uzov Christo,
Gavrailova Girka
Publication year - 1994
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1994.021950628
Subject(s) - ethylene oxide , oxide , crystal (programming language) , tetragonal crystal system , materials science , phase (matter) , crystal structure , urea , crystallography , polymer chemistry , poly ethylene , ethylene , chemical engineering , chemistry , polymer , copolymer , organic chemistry , metallurgy , catalysis , composite material , computer science , programming language , engineering
X‐ray and calorimetric investigations of the structure and transformations on heating of quenched (undercooled) samples of poly(ethylene oxide)‐urea molecular complexes are discussed. It was established that at room temperature the undercooled melt of the molecular complex contains free urea in a tetragonal crystal modification and a high‐temperature poly(ethylene oxide)‐urea molecular complex whose crystal modification does not coincide with the known hexagonal crystal structure of the molecular complex obtained from solution or by slow cooling from the melt. It was shown that on heating this molecular complex to a temperature between 87,5 and 90°C, the hexagonal crystal modification, stable at room temperature, is obtained.