Assignment of Absolute Structure of Polar Crystals Using Tailor-Made Additives. Solvent Surface Interactions on the Polar Crystals of α-Resorcinol, (R, S) Alanine and Y-Glycine

Polymer‐Induced Alignment of dl‐Alanine Nanocrystals to Crystalline Mesostructures

“…The dl-alanine morphologies observed for the single crystal, based on the work of Lahav and co-workers [59][60][61] (Figure 9a), and the suggested morphology of the primary building unit of the mesocrystals (Figure 9b), demonstrate the morphology changes to the latter. Instead of the needlelike structure obtained in the absence of polymer (Figure 9a), the lowering of interface energies by polymer adsorption, as discussed, results in a platelet with strongly exposed (001) and (00-1) faces.…”

“…The (201) and (011) faces can be easily identified as polar surfaces, from which four amino units per unit cell extrude. [59][60][61] The most polar surface, however, is the (001) face. Because the c axis in dl-alanine is the dipole axis, the (001) face is polar, with one side rich in carboxylic acids and the counterface rich in amines.…”

“…The mesocrystal, however, must be rough in the y direction, as the (010) face is not exposed in the building units. [59][60][61] b) suggested mesocrystal subunit obtained by the addition of 1 wt % PEG 4700 -PEI 1200 -S-iBAc. The morphology of the mesocrystal subunits in (b) was drawn on the basis of experimentally observed faces.…”

“…It is already known that dl-alanine is a polar crystal along the c axis; it displays well-developed "capped (201) and (011) faces" at one end of the polar c axis where ÀNH 3 + groups are exposed, and at the opposite flat (00-1) face, ÀCOO À groups are exposed. [59][60][61] We have depicted the molecular surface structure of dl-alanine, as viewed along the b and c axis, by using the program Cerius www.chemeurj.org 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim tion were not considered; the surfaces were constructed simply from the well-known unit cell of dl-alanine.…”

Variable-temperature and variable-pressure studies of small-molecule organic crystals

“…This can be achieved by irradiating solutions with intense nanosecond pulses of near-infrared laser light, 51,52 by changing solvents. 40-43, 46-48, 50, and refs therein It is also possible to inhibit the growth of the α-form, and in this way to stimulate the growth of the γ-form, by adding specially selected impurities (tailor-made additives) selectively binding to particular faces of a growing crystal, 50,[53][54][55][56][57][58] or by directing the nucleation using a Langmuir monolayer. 50,59 If the formation of the dimers in solution, and, hence, the growth of the α-polymorph, is inhibited, then the stable γ-polymorph grows under crystallization conditions closer to the equilibrium (slow crystallization), whereas very quick precipitation gives the β-polymorph.…”