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Pressure‐induced amorphization and disordering on cooling in semi‐crystalline polymers: calorimetric evidence for inverse melting in one component system
Author(s) -
Rastogi S.,
Corstjens C.S.J.,
Höhne G.W.H.
Publication year - 2001
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/1521-3900(200103)166:1<35::aid-masy35>3.0.co;2-q
Subject(s) - endothermic process , exothermic reaction , materials science , thermodynamics , crystallization , amorphous solid , polymer , isothermal process , melting point , glass transition , phase transition , crystallography , chemistry , composite material , adsorption , physics
We report some unusual phase behaviour, of general implication for condensed matter, on the polymer poly‐4‐methyl pentene‐1 (P4MP1) induced by changes in pressure ( P ) and temperature ( T ), as observed by in‐situ X‐ray diffraction and high pressure DSC. Upon increasing pressure beyond a threshold value, the polymer, crystalline at ambient conditions, looses its crystalline order isothermally. The process is reversible. This behaviour is observed in two widely separated temperature regions, one below the glass transition temperature (< 50°C) and one close to the melting temperature (250°C), thus showing solid state amorphization and inversion in the melting temperature with increasing pressure. This further suggests inverse melting, i.e. re‐entrant of the two widely separated liquid and amorphous phases along the T‐axis at fixed P . This is confirmed experimentally as disordering in the crystalline structure on cooling. The inverse melting in P4MP1 raises the possibility of exothermic melting and endothermic crystallization as anticipated by Tammann (1903), see reference 1. The anticipated exothermic melting and endothermic crystallization is confirmed experimentally in the one component system P4MP1. We are observing similar features in a range of polymers.