Controlled Nucleation and Growth of Molecular Crystals at Molecular Interfaces

小行星9408923 本研究描述了控制非均质成核的策略 和 有机晶体生长 在 分子界面，重点是基于分子晶体的特定晶面的基底的使用，以及由有机硫和有机硅烷试剂制备的自组装膜。 拟议的工作将表明，通过使用适当设计的基板，可以实现增强的成核速率，特定的生长方向，和多晶型选择性。在分子晶体衬底的情况下，这些特性将是 检查 在 分类帐导向的上下文 外延成核，其中通过聚集体的两个低能平面和几何形状相似的衬底凸缘之间的界面相互作用来稳定和定向成核前聚集体。 有机硫 和 有机硅烷 膜 提供 能够特异性地与预成核聚集体中的分子官能团相互作用的分子官能度。原子力显微镜的动态，原位，晶体生长也将进行检查。 预计这些研究将导致更好地了解负责成核和生长的有机晶体的关键因素，和合理设计的固体基质控制结晶的技术上重要的试剂和材料。 分子晶体，定义为由分子组分通过微弱但众多的分子间相互作用组装成结晶状态的固体，表现出许多性质， 基本和技术利益。 这些 包括导电性、超导性和铁磁性，非线性 光学 行为，制药 活动， 和照相感光剂。对这些材料的兴趣还源于通过分子设计合理控制体性质的能力，这种策略通常被称为"晶体工程"。"虽然有相当多的研究， 在分子晶体中，指导固态堆积的分子间相互作用、它们的成核和生长的研究，特别是在分子水平上的研究，已经相当有限。 本研究描述了在分子界面上控制有机晶体的非均质成核和生长的策略，重点是使用基于分子晶体的特定晶面的衬底，以及由有机硫和有机硅烷试剂制备的自组装膜。 拟议的工作将表明，通过使用适当设计的基板，可以实现增强的成核速率，特定的生长方向，和多晶型选择性。 ***

9408923 Ward This research describes strategies for controlled heterogeneous nucleation and growth of organic crystals at molecular interfaces, with emphasis on the use of substrates based on specific crystal faces of molecular crystals, and self-assembled films prepared from organosulfur and organosilane reagents. The proposed work will demonstrate that enhanced nucleation rates, specific growth orientations, and polymorph selectivity can be achieved through the use of properly designed substrates. In the case of molecular crystal substrates, these characteristics will be examined in the context of ledge-directed epitaxial nucleation, in which prenucleation aggregates are stabilized and oriented by interfacial interaction between two low energy planes of the aggregate and a geometrically similar substrate ledge. Organosulfur and organosilane films provide molecular functionality capable of specifically interacting with functional groups of molecules in the prenucleation aggregate. Atomic force microscopy of dynamic, in situ, crystal growth will also be examined. It is anticipated that these studies will lead to greater understanding of the critical factors responsible for nucleation and growth of organic crystals, and the rational design of solid substrates for controlled crystallization of technologically important reagents and materials. %%% Molecular crystals, defined as solids consisting of molecular components assembled in the crystalline state by weak, but numerous intermolecular interactions, exhibit numerous properties of fundamental and technological interest. These include electrical conductivity, superconductivity and ferromagnetism, nonlinear optical behavior, pharmaceutical activity, and photographic sensitizers. The interest in these materials also stems from the ability to rationally control bulk properties through molec ular design, a strategy commonly referred to as "crystal engineering." While there has been considerable study of the intermolecular interactions that direct solid-state packing in molecular crystals, investigations of their nucleation and growth, particularly at the molecular level, has been rather limited. This research describes strategies for controlled heterogeneous nucleation and growth of organic crystals at molecular interfaces, with emphasis on the use of substrates based on specific crystal faces of molecular crystals, and self-assembled films prepared from organosulfur and organosilane reagents. The proposed work will demonstrate that enhanced nucleation rates, specific growth orientations, and polymorph selectivity can be achieved through the use of properly designed substrates. ***