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Kinetics of Phase Transitions in Amorphous Carbamazepine: From Sub-Tg Structural Relaxation to High-Temperature Decomposition
Year: 2025
Type of publication: článek v odborném periodiku
Name of source: International Journal of Molecular Sciences
Publisher name: MDPI (Multidisciplinary Digital Publishing Institute)
Place: Basel
Page from-to: 6136
Titles:
Language Name Abstract Keywords
cze Kinetika fázových přechodů v amorfním karbamazepinu: od sub-Tg strukturní relaxace k vysokoteplotnímu rozkladu Termokinetická charakterizace amorfního karbamazepinu byla provedena s využitím neizotermické diferenční skenovací kalorimetrie (DSC) a termogravimetrie (TGA). Strukturní relaxace amorfní matrice byla popsána pomocí modelu Tool-Narayanaswamy-Moynihan. Krystalizace amorfní fáze byla modelována pomocí komplexní Sestak-Berggrenovy kinetiky, která zahrnuje teplotně závislou aktivační energii a stupeň autokatalýzy. Aktivační energie růstu krystalů byla stanovena na >320 kJ/mol při teplotě skelného přechodu. karbamazepin; strukturní relaxace; růst krystalů; tepelný rozklad
eng Kinetics of Phase Transitions in Amorphous Carbamazepine: From Sub-Tg Structural Relaxation to High-Temperature Decomposition Thermokinetic characterization of amorphous carbamazepine was performed utilizing non-isothermal differential scanning calorimetry (DSC) and thermogravimetry (TGA). Structural relaxation of the amorphous matrix was described in terms of the Tool-Narayanaswamy-Moynihan model with the following parameters: Delta h* approximate to 200-300 kJ center dot mol(-1), beta = 0.57, x = 0.44. The crystallization of the amorphous phase was modeled using complex Sestak-Berggren kinetics, which incorporates temperature-dependent activation energy and degree of autocatalysis. The activation energy of the crystal growth was determined to be >320 kJ center dot mol(-1) at the glass transition temperature (T-g). Owing to such a high value, the amorphous carbamazepine is stable at T-g, allowing for extensive processing of the amorphous phase (e.g., self-healing of the quench-induced mechanical defects or internal stress). A discussion was conducted regarding the converse relation between the activation energies of relaxation and crystal growth, which is possibly responsible for the absence of sub-T-g crystal growth modes. The high-temperature thermal decomposition of carbamazepine proceeds via multistep kinetics, identically in both an inert and an oxidizing atmosphere. A complex reaction mechanism, consisting of a series of consecutive and competing reactions, was proposed to explain the second decomposition step, which exhibited a temporary mass increase. Whereas a negligible degree of carbamazepine degradation was predicted for the temperature characteristic of the pharmaceutical hot-melt extrusion (similar to 150 degrees C), the degradation risk during the pharmaceutical 3D printing was calculated to be considerably higher (1-2% mass loss at temperatures 190-200 degrees C). carbamazepine; structural relaxation; crystal growth; thermal decomposition

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