Manipulating Crystal Orientation in Nanopores
Recent research from the groups of Professor Marc Hillmyer.
Investigators at the University of Minnesota MRSEC and the New York University MRSEC have reported the growth of glycine nanocrystals inside aligned cylindrical nanopores of a polymer monolith that was derived from an ordered block polymer precursor. The size confinement imposed by the nanopores stabilizes the least stable beta polymorph, and the crystals grow with their native fast-growth direction aligned parallel with each pore. Furthermore, selective binding of racemic auxiliaries (circled) to the crystal face (red) perpendicular to this direction results in faster growth along a different crystal direction, which changes the crystal orientation. This behavior can be attributed to a competition between differently aligned crystals due to critical size effects, the minimization of the surface energy of specific crystal planes, and a more effective reduction of the excess free energy associated with supersaturated conditions when the crystal grows with its fast-growth axis unimpeded by pore walls. See the article at J. Am. Chem. Soc. 2009, 131, 2588-2596. Supported by UMN MRSEC Awards DMR#0212302 and DMR#0819885.
Listen to JACS podcast of Marc Hillmyer and Mike Ward discussing this research: http://pubs.acs.org/JACSbeta/coverartpodcasts/index.html#podcast6