Solution-mediated phase transition

Solid-state phase transitions usually take place at a slower rate than solution-mediated phase transitions because the motion of the molecules is restricted in the solid state. Processing stresses such as grinding [28], heating [28], humidity... 

G. Fevotte, C. Alexandre and S.O. Nida, A population balance model of the solution-mediated phase transition of citric acid, AIChE J., 53, 2578-2589 (2007). 

Metastable Phases and their Transition Solution-mediated Phase Transition (SMPT)... 

Figure 9.3 Evolution with time of the solute concentration during a solution-mediated phase transition, C i and C 2 are the solubilities of the metastable and stable phases, respectively, (a) General profile, (b) limit profiles.

Third Case Study Solution-mediated Phase Transition in a Co-crystallization Process (from Gagniere et )... 

Reproducibility, not accessible for all polymorph pairs - only relates to forms involved in transition Larger sample size, solution-mediated phase transformations... 

A rate enhancement effect due to secondary nucleation has been identified in the solution-mediated transformation of the 7-phase of (i)-glutamic acid to its / -phase [82]. In this study, the kinetics of the polymorphic transition were studied using optical microscopy combined with Fourier transform infrared, Raman, and ultraviolet absorption spectroscopies. The crystallization process of n-hexatriacontane was investigated using micro-IR methodology, where it was confirmed that single... 

Based on their structural characteristics, crystalline hydrates were broken into three main classes. These were (1) isolated lattice site water types, (2) channel hydrates, and (3) ion associated water types. Class 2 hydrates were further subdivided into expanded channel (nonstoichiometric) types, planar hydrates, and dehydrated hydrates. The classification of the forms together with a suitable phase diagram provides a rationale for anticipating the direction and likelihood of a transition, including transitions that may be solution mediated. 

This type of behaviour is not confined to polymorphs but may extend to pseudopolymorphic forms such as hydrates and solvates. A recent case of solvent-mediated phase transformation involved polymorphic and pseudopolymorphic forms of thiazole carboxylic acid [55], where the transformation is again sensitive to the composition of the mixed solvent. Three forms of the compound are known, an anhydrous form, a 0.5 hydrate, and a 1.5 hydrate. In 50-80% solutions (% = vol.% MeOH-H20), transformation of the 1.5 hydrate to the 0.5 hydrate was observed while transformation to the anhydrous form occurred in 85-100% solutions. No transformation occurred in 0-30% solutions. Detailed study of a solvent-mediated polymorphic transition has also been carried out for the antiulcerative agent cimetidine [56] for which seven polymorphic forms are known. An important feature of this study was the systematic use of seed crystals to induce crystallization at different supersaturation ratios. 

Characterization of solution-mediated transformations in the amorphous state can give an insight into amorphous crystallization (Zhang et al. 2(X)9). The importance of the phase transition kinetics, molecular interpretations, and process implications has been emphasized in numerous studies (Cardew and Davey 1985 Davey et al. 1986, 1997a, 1997b Rodriguez-Homedo et al. 1992 Blagden et al. 1998). 

---