title: Effect of crystal habits on the surface energy and cohesion of crystalline powders.
abstract: The role of surface properties, influenced by particle processing, in particle-particle interactions (powder cohesion) is investigated in this study. Wetting behaviour of mefenamic acid was found to be anisotropic by sessile drop contact angle measurements on macroscopic (>1cm) single crystals, with variations in contact angle of water from 56.3° to 92.0°. This is attributed to variations in surface chemical functionality at specific facets, and confirmed using X-ray photoelectron spectroscopy (XPS). Using a finite dilution inverse gas chromatography (FD-IGC) approach, the surface energy heterogeneity of powders was determined. The surface energy profile of different mefenamic acid crystal habits was directly related to the relative exposure of different crystal facets. Cohesion, determined by a uniaxial compression test, was also found to relate to surface energy of the powders. By employing a surface modification (silanisation) approach, the contribution from crystal shape from surface area and surface energy was decoupled. By "normalising" contribution from surface energy and surface area, needle shaped crystals were found to be ∼2.5× more cohesive compared to elongated plates or hexagonal cuboid shapes crystals.
authors.affiliation: Surfaces and Particle Engineering Laboratory (SPEL), Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
authors.forename: Umang V
authors.initials: UV
authors.lastname: Shah
authors.affiliation: Bristol-Myers Squibb Pharmaceuticals, 1 Squibb Drive, New Brunswick, NJ 08903, USA.
authors.forename: Dolapo
authors.initials: D
authors.lastname: Olusanmi
authors.affiliation: Bristol-Myers Squibb Pharmaceuticals, 1 Squibb Drive, New Brunswick, NJ 08903, USA.
authors.forename: Ajit S
authors.initials: AS
authors.lastname: Narang
authors.affiliation: Bristol-Myers Squibb Pharmaceuticals, 1 Squibb Drive, New Brunswick, NJ 08903, USA.
authors.forename: Munir A
authors.initials: MA
authors.lastname: Hussain
authors.affiliation: Bristol-Myers Squibb Pharmaceuticals, Reeds Lane, Moreton, Wirral CH46 1QW, UK.
authors.forename: John F
authors.initials: JF
authors.lastname: Gamble
authors.affiliation: Bristol-Myers Squibb Pharmaceuticals, Reeds Lane, Moreton, Wirral CH46 1QW, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Tobyn
authors.affiliation: Surfaces and Particle Engineering Laboratory (SPEL), Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. Electronic address: jerry.heng@imperial.ac.uk.
authors.forename: Jerry Y Y
authors.initials: JY
authors.lastname: Heng
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D003460:Crystallization; D008528:Mefenamic Acid / Q000737:chemistry; D010316:Particle Size; D011208:Powders / Q000737:chemistry*; D013499:Surface Properties; D017155:Wettability
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D011208:Powders; D008528:Mefenamic Acid
keywords: Cohesion; Crystal aspect ratio; Crystal habit; Macroscopic single crystal; Solvent polarity; Surface energy heterogeneity