Crystallization of Organic Glasses

Transcription

1 Crystallization of rganic Glasses Ye Sun, Lei Zhu, Ting Cai, Hanmi Xi, Mariko Hasebe, Tian Wu, Hajime Ishida, Melgardt de Villliers, Mark Ediger, and Lian Yu University of Wisconsin Madison School of Pharmacy & Dept. of Chemistry With thanks to: SF, PF, AstraZeneca Crystalline and amorphous Si Crystalline Si (quartz) Density.65 g/cm 3 Amorphous Si (glass) Density. g/cm 3

2 Crystalline and amorphous indomethacin P 1, m.p. 153 ºC C H Amorphous solid (glass). T g = 4 ºC More soluble than crystals (5 17 x) Figure from Chen,, Stowell. JACS. Solubilities from Hancock & Parks, Murdande et al.. 1, Alonzo et al. 1 Cl P-1, m.p. 16 ºC Standard way to make a glass: Cooling a liquid without crystallization The glass transition region ther ways: Grinding Freeze or spray drying Drying crystalline hydrates Vapor deposition

3 Is there a problem? Can glasses really crystallize? bsidian: atural silicate glass stable for millions of years but eventually crystallizes m A spherulite growing in amorphous nifedipine at 3 ºC (T g 1 º C) H u = 4 m/day Ishida, Wu, and Yu. J. Pharm. Sci This talk Fast crystal growth in one-component organic glasses (1)A bulk mode (GC) activated near T g ()A surface mode

4 Log u, (m/s) Crystal growth rate in a one-component liquid glass TP T g liquid Thermodynamic control u D Diffusion controlled growth T m log u Magill & Li (1973) log D Mapes et al. (6) log D Fujara et al. (199) Log D, (cm /s) C Wilson, Frenkel, Turnbull: Diffusion defines kinetic barrier of crystal growth L u A new, fast growth mode ( GC ) is activated near T g Log u, (m/s) T g GC growth ot controlled by bulk diffusion Diffusion controlled growth log u Magill & Li log u Hikima et al. log D Mapes et al. log D Fujara et al T m Log D, (cm /s) First observed for TP by Greet and Turnbull in 1967 Studied by guni and coworkers since 1995 Unknown for inorganic and polymeric glass formers TP

5 GC growth at 48 K What does GC growth look like? b 1 m ormal growth at 98 K t t + 4 min GC crystals are real crystals! Same unit cell as normal crystals early the same m.p. and H m Growth is also mainly along b t + 6 min GC growth has fast-growing fibers as precursors -4-5 compact spherulites T g = 46 K 49 K fibers Compact growth Fiber growth 1 m Log u, m/s Scherer et al. Scherer et al. (protuberance) Magill & Li Hikima et al. Greet &Turnbull Greet Konishi & Tanaka This work Sun et al. J. Phys. Chem. B 8, 11, 661; Xi et al. J. Chem. Phys. 9, 13, 9458

6 Studying GC growth with polymorphs: From the same liquid/glass, which polymorph shows GC growth, and which does not? A B liquid/glass C (1) P-1 mp 16. o C = 1.7 Y polymorphs () P 1 /c mp o C = 5.6 H Y S C CH 3 (7) PL (3) Y P 1 /c mp 19.8 o C = 14.7 (4) P P 1 /c mp 11.7 o C = 46.1 (5) Y P-1, mp 99 ºC = 14.1 (6) P Pbca mp 97 ºC = 39.4 JACS. JACS 1 1 m 5 Y4 (8) Y4 L JACS 5a (9) YT4 P 1 /c mp 16.9 o C = 11.8 (1) 5 JACS 5b L

7 Some Y polymorphs show GC growth; some do not Sun, J. Phys. Chem. B 8, 11, 661 and 5594 (1) P-1 mp 16. o C = 1.7 (4) P P 1 /c mp 11.7 o C = 46.1 (7) PL JACS 1 Polymorphs of Y () P 1 /c mp o C = 5.6 (5) Y P-1, mp 99 ºC = m (8) Y4 L JACS 5a H Y (6) P Pbca mp 97 ºC, = 39.4 S C CH 3 (9) YT4 P 1 /c mp 16.9 o C = 11.8 (3) Y P 1 /c mp 19.8 o C = 14.7 J. Am. Chem. Soc., 1, (1) 5 JACS 5b Y4 L Log u, (m/s) a b GC growth (compact spherulites) y shift YT4 GC growth T g T t T t fibers o GC growth YT4 fibers (o GC growth) P YT4 Y Y + = Log u, (m/s) Crystal structures showing GC growth are more liquid like Anisotropic packing: o GC growth adial distribution functions More isotropic packing: GC growth umber of molecules Y Y P YT r, Ǻ

8 GC growth is similar kinetically to polymorphic conversion, but feels the glass transition L/G 95 K T g 1μm Y 61 K Log u, (m/s) Y G (GC) L Y 1 μm rigin of GC growth: Still an open question Bulk relaxation. But the process is absent in Y and aged away in TP Tension at crystal/glass interface. But fibers grow rapidly above T g, and no expected autocatalysis Solid-state transition similar to polymorphic conversion. But no predictive power Molecular mobility at grain-boundaries. But no predictive power

9 This talk Fast crystal growth in one-component organic glasses (1)A bulk mode (GC) activated near T g ()A surface mode Crystal growth in the bulk Crystal growth at the free surface glass crystal glass crystal Whereas in many metallic glasses nucleation has been observed to be enhanced at the surface, growth rates are usually quite comparable with those in the bulk. U. Koster (Mat. Sci. & Eng. 1988, 97, 33) [For silicate glasses,] The crystal growth velocities of crystals in the volume and of the surface layer in the glass volume, as well as of isolated crystals on the glass surface are equal. Diaz-Mora et al. (J. on-crystalline Solids, 73, 81)

10 For organic glasses, crystal growth can be much faster at the surface than in the bulk Log u, m/s Crystal growth rate of IMC ( polymorph) Glass Crystal Cover Glass surface T g Cover Glass Glass Crystal Cover Glass bulk Wu, T.; Yu, L. J. Phys. Chem. B 6, 1, 15694; Pharm. es. 6, 3, 35 What do surface crystals look like? a IMC a IMC b c µm µm 15nm b c 4µm 1µm 3nm Growth front is above glass surface Sun et al. PAS, in press

11 Growth of IMC surface crystals at ºC h 4 h 5 m 6 h 8 h Mariko Hasebe Surface crystallization of amorphous IMC can be inhibited with a nanocoating Uncoated sample 7 days at 4 ºC 15 mm Coated with 1 nm gold or 3 nm polymer μm 7 days at 4 ºC μm Wu, Sun, Li, de Villiers, and Yu. Langmuir 7, 3, 5148

12 Surface crystal layer can be quite thin cover glass (18 18 mm ) Expt. 1: Direct observation IMC glass scratch a-imc air 4µm scratch cover glass ( mm ) t = 96 hr -IMC 194 hr 98 hr Expt. : Vary glass thickness d d = 5 nm 15 m Glass Si Crystal Sun et al. PAS, in press 5µm d=1µm d=48nm 41nm nm 18nm 135nm 1nm o effect ew morphology, slower growth Surface diffusion is fast on amorphous IMC -13 b D s (surface) log D, m /s T g D v (bulk) Mobile surface Glass Lei Zhu

13 rigin for surface-enhanced crystal growth: Still an open question Surface mobility Surface crystals can exploit opportunity to grow upward Tension from crystal growth is better released at the surface than in the bulk All these models imply generality of the phenomenon. But is it? Summary: Fast crystal growth in organic glasses GC growth A new bulk growth mode is activated near T g. It is not limited by bulk diffusion Favors liquid-like structures Similar to polymorphic transformation Surface growth Surface enhances growth, not just nucleation Inhibited by nano-coating Correlates with surface molecular mobility Both modes are known only or mainly for organic glasses