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Capabilities of low‐wavenumber Raman spectroscopy for analyzing the mechanism of devitrification of molecular glasses
Author(s) -
Malfait Benjamin,
Paccou Laurent,
Derollez Patrick,
Guinet Yannick,
Hedoux Alain
Publication year - 2019
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.5606
Subject(s) - devitrification , raman spectroscopy , crystallization , metastability , phase (matter) , materials science , isothermal process , crystallography , chemistry , thermodynamics , optics , physics , organic chemistry
Abstract The mechanism of devitrification of racemic ibuprofen (RS‐IBP, C 13 H 18 O 2 ) was analyzed by low‐wavenumber Raman spectroscopy (LWRS). This study shows the capabilities of LWRS to provide detailed new structural information, with respect to X‐ray diffraction data, on the atypical crystallization process of a molecular material (RS‐IBP) composed of a majority of hydrogen atoms. The conversions of Raman intensity into reduced intensity and Raman susceptibility were presented. The combination of these two types of spectrum representation reflecting the fast relaxational dynamics and the structural organization, respectively, has clearly revealed the high degree of disorder of Phase II. Additionally, Phase II was described as an early transient and metastable step of crystallization toward Phase I, from a deeply quenched liquid state. Analyzing the isothermal and nonisothermal crystallization has revealed two types of conversion of Phase II into Phase I, a solid–solid transformation and a crystallization of Phase I after melting of Phase II, respectively.