Transformation of an active pharmaceutical ingredient upon high-energy milling: A process-induced disorder in Biclotymol

Accepted Manuscript Title: Transformation of an active pharmaceutical ingredient upon high-energy milling: A process-induced disorder in Biclotymol Author: Benjamin Schamm´e Nicolas Couvrat Pascal Malpeli ´ Emeline Dudognon Laurent Delbreilh Val´erie Dupray Eric Dargent G´erard Coquerel PII: DOI: Reference:

S0378-5173(15)30434-8 http://dx.doi.org/doi:10.1016/j.ijpharm.2015.12.032 IJP 15425

To appear in:

International Journal of Pharmaceutics

Received date: Revised date: Accepted date:

30-9-2015 10-12-2015 12-12-2015

Please cite this article as: Schamm´e, Benjamin, Couvrat, Nicolas, Malpeli, ´ Pascal, Dudognon, Emeline, Delbreilh, Laurent, Dupray, Val´erie, Dargent, Eric, Coquerel, G´erard, Transformation of an active pharmaceutical ingredient upon highenergy milling: A process-induced disorder in Biclotymol.International Journal of Pharmaceutics http://dx.doi.org/10.1016/j.ijpharm.2015.12.032 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Transformation of an active pharmaceutical ingredient upon high-energy milling: A process-induced disorder in Biclotymol Benjamin Schamm醧 [email protected], Nicolas Couvrat† [email protected], Pascal Malpeliф [email protected], Emeline Dudognon‡ [email protected], Laurent Delbreilh§* [email protected], Valérie Dupray†* [email protected], Éric Dargent§ [email protected], Gérard Coquerel† [email protected] †

Normandie Univ, Crystal Genesis Unit, Laboratoire SMS- EA3233, Univ Rouen, F-76821,

Mont Saint Aignan, France. §

AMME-LECAP EA 4528 International Lab, Avenue de l’Université, BP12, Normandie

Université France, Université and INSA Rouen, 76801 Saint Etienne du Rouvray, France. ‡

UMET (Unité Matériaux et Transformations) UMR CNRS 8207, Bat P5 F-59655, Université

Lille 1, Villeneuve d’Ascq, France. ф

Pharmasynthese (Inabata Group), Saint Pierre Les Elbeuf, 76320, France.

*

Corresponding authors. Tel.: +33 2 32 39 90 82 (Valérie Dupray); Tel.: +33 2 32 95 50 84

(Laurent Delbreilh).

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Graphical abstract

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Abstract This study investigates for the first time the thermodynamic changes of Biclotymol upon highenergy milling at various levels of temperature above and below its glass transition temperature (Tg). Investigations have been carried out by temperature modulated differential scanning calorimetry (TM-DSC) and X-ray powder diffraction (XRPD). Results indicate that Biclotymol undergoes a solid-state amorphization upon milling at Tg-45°C. It is shown that recrystallization of amorphous milled Biclotymol occurs below the glass transition temperature of Biclotymol (Tg = 20°C). This displays molecular mobility differences between milled Biclotymol and quenched liquid. A systematic study at several milling temperatures is performed and the implication of Tg in the solid-state transformations generally observed upon milling is discussed. Influence of analysis temperature with respect to interpretation of results was investigated. Finally, it is shown that co-milling Biclotymol with only 20 wt % of amorphous PVP allows a stable amorphous dispersion during at least 5 months of storage.

Keywords:

Amorphous;

Biclotymol;

Glass

transition;

Milling;

Pharmaceuticals;

Polyvinylpyrrolidone; Stability

Chemical compounds studied in this article:Biclotymol (PubChem CID: 71878); Polyvinylpyrrolidone (PubChem CID: 6917)

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1. Introduction Downstream operations such as drying, micronization, compression or grinding tend to stress crystalline molecular compounds which over-express their initial imperfections. High-Energy Milling (HEM hereafter) has been integrated to pharmaceutical development mainly to reduce particle size (Liversidge and Cundy, 1995). Indeed, an accurate control of granulometry of molecular compounds leads to an enhanced ability to dissolve, a facilitated tablet compression and an improved control of dosages (Brittain, 2002) (Branham et al, 2012). However, such downstream operations can induce changes in the physical state of the product, eg. in the structural purity (Coquerel, 2006). Indeed, numerous pharmaceutical compounds (Active Pharmaceutical

Ingredients

and

excipients)

are

known

to

undergo

polymorphic

transformations (Zhang et al, 2002) (De Gusseme et al, 2008) as well as solid-state amorphization (Font et al, 1997) (Wojnarowska et al, 2010) (Karmwar et al, 2011) (Xu et al, 2015) upon milling operations. Amorphous materials obtained by milling are usually less physically stable compared to amorphous samples obtained by the fast cooling of a molten sample, and tend to crystallize over time towards a more stable state (Andronis and Zografi, 2000) (Crowley and Zografi, 2002). This non-equilibrium transformation significantly affects the bioavailability and the ability to dissolve. In this way, solid-state transformations of molecular compounds must be rationalized for the development of a dosage form (Morris et al, 2001). Thus, the life expectancy of the amorphous state has to be addressed and optimized to secure protocols of formulation (Bhugra and Pikal, 2008). In recent years, a great effort has been dedicated to the study of “crystal to glass transformation” induced by milling (Wojnarowska et al, 2013) (Descamps et al, 2015). To date, a streamlining of transformations reached by milling has not been attained even if some empirical rules are emerging from current investigations (Dujardin et al, 2013). Physical parameters such as milling temperature, intensity and duration have been shown to play an important role in the reached stationary states (Descamps et al, 2007). It is accepted that milling must be performed at temperatures 4   

lower than the glass transition temperature (Tg) to reach a stationary amorphous state. Moreover, it has been reported that the higher the milling intensity, the better the efficiency of the amorphization process (Desprez and Descamps, 2006). In this way, we used the opportunity provided by molecular compounds to have their glass transition temperature located near room temperature to investigate the importance of the milling temperature with respect to Tg. Biclotymol is an active pharmaceutical ingredient used for the treatment of otolaryngology infections. Crystal structure of commercial raw material which consists of anhydrous stable Form I was solved by Rantsordas et al. (Rantsordas et al, 1978) several years ago (Cambridge Structural Database (CSD-MYCMPP)). More recently, a metastable crystalline form has been highlighted through thermal analyses starting from amorphous Biclotymol and the relative stability of these two polymorphs as a function of pressure and temperature was reported (Ceolin et al, 2008). Moreover, a recent study (Tripathi et al, 2015) employed employ broadband dielectric spectroscopy to monitor relaxation dynamics of Biclotymol in its amorphous phase. Biclotymol exhibits a glass transition temperature at Tg = 20°C which gives the opportunity to perform high-energy milling operations above and below Tg. In the previous investigation by Schammé et al, vitrification properties of Biclotymol by meltquenching were considered (Schammé et al, 2015). Herein we present an investigation of structural transformations of this crystalline molecular compound upon high-energy milling. Special attention has been paid to investigate the effect of HEM at several temperatures above and below Tg. 2. Materials and methods 2.1. Materials Biclotymol crystalline powder (C21H26Cl2O2, Mw = 381.32 g/mol), was supplied by Pharmasynthese (Inabata group) and was used without further purification. Commercial 5   

amorphous Polyvinylpyrrolidone (see Figure A, supporting information) (PVP, (C6H9NO)n, Mw = 40000 g/mol) was purchased from Fisher Bioreagents and used as received. The developed formulae of Biclotymol and PVP molecules are shown in Figure 1. 2.2 High-Energy Milling (HEM) operations Milling experiments were performed in a high energy planetary mill “Pulverisette 7”, Fritsch. Room temperature milling experiments were conducted at 25°C (Tg + 5°C) with two milling jars of 80 mL made of zirconium oxide containing ten balls (Ø = 10 mm) of the same material. Each milling operation was conducted with 1 g of Biclotymol powder. Milling experiments at -10°C (Tg – 30°C) were conducted by placing the whole milling device inside a temperature-controlled chamber. Two milling jars of 43 mL made of zirconium oxide containing seven balls (Ø = 15 mm) of the same material were used. Each milling operation was conducted with 1.5 g of Biclotymol powder. For both milling temperatures, the vial rotation speed ω was set up to 400 rpm. The rotation of the solar disk, Ω, was performed in the opposite direction compared to the vials. One milling program of milling periods of 20 min and pauses of 10 min was used. These milling conditions have been arbitrarily chosen to limit the mechanical heating of the samples. Each experiment was conducted on a fresh crystalline sample. Co-milling with PVP was conducted with two milling jars of 80 mL (ZrO2) containing three balls (Ø = 20 mm) of the same material. An effective 10 h milling experiment (milling periods of 5 min alternated with pauses of the same duration) was conducted with 1 g of material at 4°C with (Ω ; ω) set to (400 ; -400). 2.3 Milling-Quenching operations

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Milling-quenching experiments were carried out using a mixer mill “MM 400”, Retsch. One milling jar of 10 mL made of zirconium oxide containing one ball of the same material (Ø = 12 mm) was used. Milling operations were conducted with 1.5 g of Biclotymol powder. Jar was pre-cooled under liquid nitrogen during 5 min and sample was milled for 5 min at a frequency of 30 Hz. Between each milling session, the closed jar was immersed in liquid nitrogen for quench cooling during at least 30 s. These milling conditions have been established to limit the mechanical heating of the samples and to maintain the temperature of the jar as cool as possible. With a thermocouple, temperature of the jar was ascertained and found to be at circa -25°C. 2.4 Temperature Modulated Differential Scanning Calorimetry (TM-DSC) and Differential scanning calorimetry (DSC) TM-DSC experiments were performed using a TA Instruments Q100 DSC coupled with a liquid nitrogen cooling system. Baseline was calibrated from 0°C to 150°C with an oscillation amplitude of ± 0.531 °C and oscillation period of 40 s with a heating rate of 5 K/min. Analysis of co-milled mixtures was performed with a Netzsch DSC 204 F1 apparatus equipped with an intracooler. Sample masses of 5 ± 0.5 mg were enclosed into 25 µL aluminum pans with pierced lids. A heating rate of 10 K/min was used for each experiment. The atmosphere of the analyses was regulated by a helium flux (40 mL/min). 2.5 X-ray Powder diffraction (XRPD) XRPD analyses were recorded using an X'pert Pro MPD from PANalytical. Cu Kα radiation (λ = 1.541 Å) and a θ - θ Bragg-Brentano geometry was used as reference configuration. Powder sample was placed in an Anton-Paar TTK 450 cryostat (-193°C - 0°C) and analyzed at -10°C and 25°C from 5 to 60° (2θ) with 50 seconds per step (duration 23 min) and a step size of 2° (2θ). 7   

XRPD analyses of co-milled systems were recorded on a benchtop INEL Equinox 100 diffractometer, mounted with a copper micro focus tube (λ = 1.541 Å), equipped with a curved detector. The acquisitions are performed by reflexion in real time up to 110° in 2θ, at 40 kV, 10 mA with a metal rotating sample holder. Spinning sample holder minimizes the effects of preferential crystallization. Sample holder dimensions was Ø 15mm in diameter and Ø 0.5mm in thickness. XRPD duration was of 10 min and performed directly after the production of samples. Data processing of crystalline and milled compounds was performed through FullProf Suite software (Rodriguez-Carvajal, 1990)” 3. Results and Discussion 3.1 Previous works: melt-quenching of stable Form I Biclotymol is an active pharmaceutical ingredient which exists in two crystalline varieties, one stable (Form I) and one metastable (Form II) in a monotropic relationship (Ceolin et al, 2008). This compound can be easily vitrified and displays upon reheating a clear defined Cp jump indicating the glass transition (Figure 2B). Thermodynamic properties of Biclotymol (melting and crystallization temperatures) are reported in Table 1 and were found to be consistent with our recently published work (Schammé et al, 2015). Moreover, on the XRPD pattern recorded straightaway after melt-quenching, characteristic Bragg peaks of Form I have vanished, as clearly illustrated by the diffusion halo (Figure 2A). This indicates, in agreement with the DSC results, that the sample obtained by quenching the fused Biclotymol is amorphous vitreous.

3.2 Milling of stable Form I above Tg (at 25°C, Tg + 5°C) Biclotymol was milled during a 80 h effective milling time at 25°C (Tg + 5°C). On the resulting diffractogram obtained at room temperature (see Figure B, supporting information), the Bragg peaks of Form I are still present. Only a slight broadening of the Bragg peaks is 8   

observed, suggesting that milling under these conditions has only an effect on the size of the resulting crystallites. Indeed, it was noticed that full widths at half maximum (FWHM) are higher for milled sample at RT compared to Form I. This observation supports the hypothesis of a size reduction of the crystallites (see Table A, supporting information). 3.3 Milling of stable Form I below Tg (at -10°C, Tg - 30°C) Diffractogram (b) on Figure 3 was recorded at -10°C immediately after that Biclotymol was milled 10 h at -10°C. A significant decrease of the intensity of stable Form I characteristic Bragg peaks is noticed. Moreover, a broadening (increased FWHM) is observed, which indicates a size reduction of the crystallites without inducing a visible solid state vitrification of the sample. Additionally, a sample of Biclotymol milled 10 h at -10°C and analyzed after 8 h storage at 25°C displays almost the same XRPD pattern aside from the intensity of Bragg peaks (Figure 3 (c)). Complementary to XRPD results, a TM-DSC analysis was performed. The thermogram (Figure 4 (b)) of sample milled 10 h at -10°C (analyzed directly after production) reveals an exothermic event at Tc onset = 22.9°C (Tpeak = 29.6°C) corresponding to the crystallization of an amorphous fraction of Biclotymol upon heating. Calculation of amorphous fraction of milled Biclotymol can be practically done with a DSC heating scan. The amorphous fraction is determined from the enthalpies of crystallization and melting, respectively. However, a simple ratio of these enthalpies cannot provide a correct estimation. As crystallization occurs between the glass transition temperature (Tg) and the melting temperature (Tm), recrystallization enthalpy is lower than the one of fusion. The precise determination of amorphous fraction consists in the calculation of the expected enthalpy at the crystallization temperature (Tcr) for a fully amorphous sample. Therefore, the ratio of the enthalpy of crystallization measured experimentally ∆

by the value of the enthalpy of

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crystallization calculated at Tcr (∆

) corresponds to the amorphous fraction (Xam) in

the sample (Eq. 1):



∆



∆ ∆



.1

can be calculated from the melting enthalpy (by considering the ∆Cp independent

of the temperature) with Eq. 2 (Lefort et al, 2004): ∆

∆

∆



.2

Calculation shows that circa 18 ± 4 % of the initial mass crystallize during heating (and thus have been amorphized). Additionally, the onset of melting (Tm onset) of the milled sample with regards to crystalline Form I is slightly shifted towards lower temperatures. Usually referred as Gibbs Thomson effect (Jackson and McKenna, 1990), this indicates a size reduction of the crystallite induced by milling. 3.4 Milling-quenching operations (at -25°C, Tg - 45°C) In this part of the study, a lower milling temperature (located 45°C below Tg of Biclotymol) was investigated. Jar was immersed in liquid nitrogen for quench cooling between each milling session that lasted five minutes. Measurement of the external temperature of the jar indicated that the milling was performed at least below -25°C (i.e. 45°C below the Tg of Biclotymol). Figure 5 shows the X-ray diffraction patterns of (a) sample milled 90 min below Tg (-25°C) recorded at -10°C, (b) sample milled 90 min below Tg (-25°C) recorded at 25°C and (c) unmilled. For the sample recorded at -10°C just after milling, the quasi-total disappearance of the characteristic Bragg peaks and a diffuse amorphous halo is observed. However, the analysis of the same sample at room temperature, performed after production, shows characteristic Bragg peaks of the stable Form I.

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The DSC run (Figure 6 (b)) of sample milled 90 min at -25°C (analyzed directly after production) presents an exothermic event at Tc onset = 12.9°C (Tpeak = 18.9°C). The enthalpy of the exothermic DSC peak shows that circa 68 ± 4 % of the milled sample crystallizes during heating. Moreover, as depicted above, the melting is also slightly depressed due to the size reduction of the crystallites induced by milling. It should be emphasized that X-ray diffraction is a static analysis whereas DSC is a dynamic analysis. Indeed, the recording time of a diffractogram is of 23 min whereas with the DSC apparatus the time to go from -10°C to room temperature is of 7 min. The thermodynamic properties of milled samples are reported in Table 2.

3.5 Co-milling operations with PVP (at 4°C) In an attempt to prevent the recrystallization process when milled samples are analyzed at room temperature and also to improve the stability of this active pharmaceutical ingredient in its amorphous state, the possibility exists to form a glassy amorphous molecular alloy by spray-drying (Corrigan et al, 2004) or by milling together pure crystalline powder of Biclotymol with a high Tg excipient (Willart et al, 2006) (Patterson et al, 2007). This special procedure ensures a higher glass transition temperature as it obeys to the Gordon Taylor law (Gordon et al, 1977). The difference between the glass transition temperature and the milling temperature will be increased and might result in strengthening the amorphization tendency. Moreover, a higher glass transition temperature might result to a lower tendency to recrystallize. To this purpose, an amorphous polymer as polyvinylpyrrolidone (PVP), known in the pharmaceutical industry to stabilize amorphous forms (Caron et al, 2013) or to inhibit polymorphic transformation (Baaklini et al, 2015), was used as excipient for the co-milling procedure.

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Figure 7 (A) shows the X-ray diffraction patterns of co-milled blends as a function of the percentage of Biclotymol recorded immediately after production. The halo pattern as well as the absence of Bragg peaks indicates that all isolated mixtures were X-ray amorphous. Moreover, as stability of formulations is prominent in the pharmaceutical industry, amorphous dispersions were stored at room temperature for 22 weeks under P2O5 (due to hygroscopic character of PVP). XRPD analyses at room temperature display full X-Ray amorphous samples after 5 months of storage (Figure 7 (B)). In this way, these results demonstrate that amorphous dispersions of Biclotymol with PVP could be produced with a low excipient concentration (20% wt). Therefore, one could consider that PVP prevents the crystallization of amorphous Biclotymol obtained upon milling. 3.6 Discussion The present study shows that Biclotymol appears to follow the tendency of solid-state amorphization which stands that milling should provide an amorphous form of the compound when performed well below the glass transition temperature Tg (Descamps et al, 2007). Indeed, many studies have highlighted that milling molecular compounds below their respective glass transition induces solid-state amorphization (Willart and Descamps, 2008) (Megarry et al, 2011) or either polymorphic transformations (Shakhtshneider, 1997). Additional work from Nagahama et al. (Nagahama et al, 2000) revealed that mechanisms governing solid-state amorphization are intrinsically related to the milling temperature and its difference with respect to the glass transition. Study reported that glucose, C6H12O6, cannot be amorphized by HEM performed 13°C below the glass transition temperature (even after 300 h of milling). However, another attempt has been made to probe solid-state amorphization of glucose, by performing investigations at temperature well below Tg (Dujardin et al, 2008). As a matter of fact, for glucose, milling at 53°C below Tg has induced a clear direct transformation from crystalline to amorphous state. In this way, Dujardin et al. (Dujardin et 12   

al, 2008) described a competitive process where the introduction of disorder (efficient at low temperature) would be counterbalanced by the crystallization tendency of molecular compounds (more effective at high temperature). For high-energy milling experiments performed above Tg (25°C, Tg + 5°C), Biclotymol does not undergo a polymorphic transformation or amorphization. However, when milled far below its glass transition temperature (-25°C, Tg - 45°C) milling induces a crystal to glass transformation as confirmed by XRPD and DSC analyses. In the present case of Biclotymol, we clearly detected signatures of an amorphous fraction: (i) a broad amorphous halo depicted by the X-ray diffraction pattern; (ii) a small exotherm of crystallization in the DSC scan located at Tonset = 12.9°C upon heating the amorphous fraction. The ‘apparent’ non-amorphization of Biclotymol upon milling at -10°C (Tg - 30°C) seems to arise from a prompt recrystallization process when milled samples are analyzed at room temperature. Indeed, the XRPD analyses performed at -10°C revealed that a crystallinity barrier has been overcome to reach an X-Ray amorphous sample whereas the sample analyzed after return to room temperature (25°C) displays Bragg peaks related to the stable Form I. A validation of this scenario can be obtained by considering the DSC analysis of the 10 h milled sample at – 10°C and the 90 min milled sample at -25°C. The exothermic events related to the crystallization of the amorphous fraction occur at Tc onset = 22.9°C and 12.9°C respectively, meaning that the amorphous character cannot be experimentally observed at room temperature since the sample has undergo a crystallization process. It should be highlighted that kinetics of recrystallization between -10°C and -25°C milling operations appear to be different due to a disorder competition induced by milling and stored energy. Moreover, detection threshold of XRPD has often been reported to be around 5 wt%, therefore, residual nuclei may be present in the milled compound, leading to faster recrystallization. Indeed, amorphous materials may contain residual seeds that X-ray 13   

experiments wouldn’t be efficient to detect. As a matter of fact, a thermal analysis of a glassy compound would indicate a glass transition region whereas only a melting process would be revealed for a nanocrystalline material (Bates et al, 2006). A further confirmation of a prompt crystallization process arises from the recrystallization of milled samples toward the stable Form I rather than the metastable Form II. Indeed, meltquenched Biclotymol samples have been shown to always recrystallize upon heating into the metastable form II (Schammé et al, 2015). Thus, the prompt recrystallization below the glass transition temperature appears to originate from a self-seeded process, evidencing that the sample has not been fully amorphized. In addition, the life expectancy of amorphous pharmaceuticals during their storage at room temperature and ambient pressure is a subject of interest in the pharmaceutical industry. As milled Biclotymol would not be suitable from an application point of view, amorphous dispersions containing various ratio of PVP (20%, 40%, 60% and 80%, respectively) were prepared. We noticed that PVP inhibits the recrystallization of Biclotymol, regardless the percent of PVP. Moreover, even if only 20 % wt of PVP is sufficient to obtain an X-Ray amorphous system, the corresponding DSC heating run displays the melting of residuals crystal of Form I (see Figure D, Figure E and Figure F, supporting information). It should be noted that co-milled blends are all stable after 5 months of storage at room temperature. Moreover, at the analysis temperature (-10°C) namely 30°C below the glass transition temperature of Biclotymol, the molecular mobility of milled Biclotymol seems to be different compared to that of the quenched liquid. This situation is startling as a study carried out onto melt-quenched Biclotymol revealed no recrystallization during storage at room temperature (Schammé et al, 2015). This difference in terms of mobility could be found into the “secondary” local and faster β-relaxations processes. As sub-Tg relaxations are often believed to be one possible way to explain the origin of some crystallization phenomena, a perspective 14   

of interest would be to evaluate the mobility in Biclotymol obtained by the melt-quenching technique as well by milling. Detection of dynamical variations between these two states could provide further details as to characterize the energy landscape of this molecular compound. 4. Conclusion Herein, we studied the structural changes of crystalline Biclotymol upon high-energy milling at various temperatures and milling intensities. The investigations presented in this paper were carried out above Tg (at room temperature) and below Tg (at -10°C and -25°C). The results indicate that Biclotymol undergoes a direct crystal to glass transformation upon milling at -25°C (Tg – 45°C). The physical amorphous state reached upon milling seems to be highly dependent of the milling temperature with regards to the glass transition temperature. A competition between introduction of disorder and recrystallization takes place in the case of Biclotymol, revealing that milling leads to a dynamical stationary state which is not thermodynamically stable (which can evolve rapidly when HEM operations are stopped and could induce bias). A self-seeded process during milling experiments seems to explain the incomplete amorphization of Biclotymol upon milling. Moreover, a crystallization occurring below the glass transition temperature when Biclotymol is milled 90 min at -25°C appears to demonstrate that molecular mobility of milled Biclotymol seems to be different compared to that of the quenched liquid. Finally, we demonstrated that producing amorphous dispersions of Biclotymol with PVP could increase the glass transition temperature of the co-milled system and stabilize this compound in its amorphous form. Thus, Biclotymol constitutes an interesting case as this compound is not only difficult to amorphize but also presents a huge capacity to crystallize even when milled samples are stored at a temperature below Tg. It is thus important to pay a particular attention to the choice of adequate analyses conditions

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(temperature, duration…) in order to avoid bias in the interpretation of the experimental results. Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest. Acknowledgements The Region Haute Normandie is acknowledged for financial support to B. Schammé via the E.D. No. 351 (SPMII). The authors would like to acknowledge Nicolas Theret and Charles Thebault for some of the co-milling experiments. Thanks are also due to the ANR Mi-PhaSol.

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Figure Captions

Figure 1. Developed formulae of (a) Biclotymol (2,2'-Methylenebis(3-methyl-4-chloro-6isopropylphenol)) and (b) Polyvinylpyrrolidone (PVP). Figure 2. (A) XRPD patterns recorded at room temperature from Biclotymol samples (a) Melt-Quenched sample; (b) Crystalline stable Form I. (B) TM-DSC curves of (1) Crystalline and (2) Amorphous Biclotymol at 5 K/min heating rate. Figure 3. XRPD patterns of (a) Crystalline Form I recorded at 25°C, (b) 10 h milling at -10°C (recorded at - 10°C just after milling), (c) 10 h milling at -10°C (recorded at 25°C after a 8 8 h storage at 25°C). Figure 4. TM-DSC heating scans (± 0.531 K, oscillation period of 40 s, heating rate of 5 K/min) of (a) Crystalline stable Form I; (b) Sample milled 10 h below Tg (-10°C). Figure 5. XRPD patterns of (a) 90 min milling at -25°C (recorded at -10°C), (b) 90 min milling at -25°C (recorded at 25°C), (c) Crystalline Form I recorded at 25°C. Figure 6. TM-DSC heating scans (5 K/min) of (a) Crystalline stable Form I; (b) Sample milled 90 min below Tg (-25°C). Figure 7. (A) XRPD patterns recorded at room temperature right after milling at 4°C of Biclotymol/PVP blends containing 20, 40, 60 and 80 % wt of Biclotymol. (B) XRPD patterns recorded at room temperature of the same samples after 5 months of storage at room temperature under P2O5.  

 

21   

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Tables Table 1. Thermodynamic properties of Biclotymol obtained from temperature-modulated calorimetry with a heating rate of 5 K/min, a modulation of ± 0.531 °C and amplitude of 40 s. Value of ∆Cp extracted from TM-DSC experiments and used for the calculations of the crystallized fraction is displayed in Figure C (see supporting information).

Tg (°C)

ΔCp (J/(g.K))

20

0.45

Form I ΔHm (J/g) Tm onset (initial (°C) crystal) 125.6 104.8

Form II Tc onset (°C)

ΔHc (J/g)

Tm onset (°C)

69.5

70.8

99.2

   

 

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ΔHm (J/g) (after recryst) 84.8

Table 2. Thermodynamic properties of milled sample of Biclotymol (heating rate of 5 K/min, modulation of ± 0.531 °C and amplitude of 40 s) Samples Sample milled 10 h below Tg (at -10°C) Sample milled 90 min below Tg (at -25°C)

Tc onset (°C) 22.9 12.9

 

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ΔHc (J/g) 9.1 32.7

Tm onset (°C) 124.3 124.3

ΔHm (J/g) 96.9 98.6