Polymorphism in containerless crystallization

David Ehre, Ke Fang, Janice E. Aber, Stephen Arnold, Michael D. Ward, Bruce A. Garetz

Research output: Contribution to journalArticle

Abstract

The effect of the ambient relative humidity (RH) on the crystallization of malonic and glutaric acid in aqueous microdroplets was investigated using an electrodynamic balance (EDB). Aqueous droplets containing a solute were injected into a chamber maintained at selected RH values, after which the RH was cycled to characterize crystallization and deliquescence behavior. Glutaric acid crystals that were formed at >40% RH deliquesced at 85 ± 2% RH, consistent with the metastable α polymorph. Glutaric acid crystals initially formed at ≥30% RH, however, deliquesced at 90 ± 2% RH, corresponding to the stable β polymorph. These polymorph identifications were confirmed using in situ Raman spectroscopy. In the case of malonic acid, the mass change measured with the EDB at deliquescence revealed the formation of a hydrate, C3H4O4•1.5H2O, when the crystals were initially formed at ≥20% RH. The EDB response for malonic acid crystals initially formed at ∼5% RH, however, corresponded to an anhydrous form. These observations suggest that, contrary to expectation, metastable crystals were favored at lower supersaturation levels compared with their respective stable forms. This unanticipated behavior is attributed to nucleation within the droplet at the higher RH value but at the air-solution interface of the droplet for lower RH values.

Original languageEnglish (US)
Pages (from-to)4572-4580
Number of pages9
JournalCrystal Growth and Design
Volume11
Issue number10
DOIs
StatePublished - Oct 5 2011

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polymorphism
Crystallization
Polymorphism
humidity
Atmospheric humidity
crystallization
Electrodynamics
Crystals
acids
Acids
electrodynamics
crystals
Supersaturation
supersaturation
Hydrates
hydrates
Raman spectroscopy
solutes
Nucleation
chambers

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Polymorphism in containerless crystallization. / Ehre, David; Fang, Ke; Aber, Janice E.; Arnold, Stephen; Ward, Michael D.; Garetz, Bruce A.

In: Crystal Growth and Design, Vol. 11, No. 10, 05.10.2011, p. 4572-4580.

Research output: Contribution to journalArticle

Ehre, David ; Fang, Ke ; Aber, Janice E. ; Arnold, Stephen ; Ward, Michael D. ; Garetz, Bruce A. / Polymorphism in containerless crystallization. In: Crystal Growth and Design. 2011 ; Vol. 11, No. 10. pp. 4572-4580.
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