Organic Crystal Growth on Flexible Templates

毛光召，韦恩州立大学“柔性模板上的有机晶体生长“本项目将探索使用聚合物模板对有机晶体进行形态控制和限制的可能性。模型有机染料的成核和结晶将在二维（2-D）模板上进行研究，并在三维（3-D）壳层原子力显微镜和其他原位方法。本研究的目的是（1）了解聚电解质对有机结晶的影响;（2）将有机晶体封装在聚电解质壳层中。本研究探索了聚电解质表面结构与初生晶体习性之间的丰富相互作用。聚电解质通过晶格离子的预富集、几何和立体化学匹配、特异性相互作用和吸附诱导稳定化等途径发挥模板作用。聚合物衬底不同于无机模板，因为它们不显示外延机制中隐含的顺序和刚性。然而，已知天然聚合物诱导具有均匀习性的晶体，其不同于在没有聚合物的情况下生长的那些晶体。生物矿化研究表明，聚电解质的模板效应不需要与无机对应物相同程度的几何匹配。聚电解质由于其许多表面构象而可显示丰富的立体化学控制。对于给定的晶面，可能存在若干几何匹配。突出到溶液中的片段可以稳定初生晶体的侧面。基于上述概念，一种主要由实验组成的方法，但也利用Cerius 2程序，将被用来研究纳米模板和新生染料晶体之间的界面结构。最初的实验将集中在2-D薄膜上的染料结晶，使动力学和晶体习性修改可以在分子尺度上探测。动力学参数包括临界过饱和度、pH、诱导时间和结晶速率。晶体习性变量包括尺寸、形状取向和与模板结构的相关性。在第二阶段，研究将集中在染料结晶内壳。壳层将由可渗透小极性分子但不能渗透其晶体的多层膜组成。除了聚电解质，支持磷脂双层将被用作模板，因为它们提供了中间秩序和灵活性。该项目旨在作为概念验证研究。未来的工作可以超越一般的聚电解质，使用更高的结构定义的聚合物，如两亲性聚合物，离聚物，和biopolymers.This研究可能有更广泛的影响，在其关系的概念，纳米科学和技术，特别是在材料加工，彩色显示，信息存储，纳米复合材料，药物封装和传感器等领域。 例如，包封的胶体可以用作微量移液器的吸头，用作检测污染物的化学传感器，以及用作多相催化剂。继续探索有机模板生长的分子机制，在封装，涂层和材料加工中具有潜在的应用。这也将有助于中国人民解放军与国外研究机构建立长期的合作和交流：马克斯普朗克胶体和界面研究所。一些实验将在研究所进行，采用研究所没有的一些表征方法。的家乡机构。计划的教育和推广活动包括将研究课题纳入材料工程课程，与世界桥计划相关的全球教育，在科学夏令营计划中指导底特律高中学生，以及培训当地社区学院的科学教师。

Guangzhao Mao, Wayne State University"Organic Crystal Growth on Flexible Templates"This project will to explore the possibility of morphological control and confinement of organic crystals using polymeric templates. The nucleation and crystallization of model organic dyes will be studied on two-dimensional (2-D) polyelectrolyte templates, and in three-dimensional (3-D) polyelectrolyte shells by atomic force microscopy and other in situ methods. The proposed research aims at (1) understanding the effect of polyelectrolytes on organic crystallization; and (2) encapsulating organic crystals in polyelectrolyte shells.This research explores the rich interplay between the surface structure of polyelectrolytes and the habit of nascent crystals. Polyelectrolytes exert templating effect via preconcentration of lattice ions, geometric and stereochemical match, specific interactions, and adsorption-induced stabilization. Polymeric substrates differ from inorganic templates in that they do not show the order and rigidity implicit in the epitaxial mechanisms. However natural polymers are known to induce crystals of a uniform habit that is different from those grown without the polymers. Research in biomineralization has shown that the templating effect of polyelectrolytes does not require the same degree of geometric match as the inorganic counterparts. Polyelectrolytes may display rich stereochemical control because of their many surface conformations. There may exist several geometric matches for a given crystal face. Segments protruding into solution may stabilize side faces of the nascent crystal. Based on the above notions, an approach consisting primarily of experiments, but also utilizing the Cerius2 program, will be used to study the interfacial structure between the polyelectrolyte template and the nascent dye crystal. Initial experiments will focus on the crystallization of dyes on 2-D thin films so that the kinetics and crystal habit modification can be probed at the molecular scale. The kinetic parameters include critical supersaturation, pH, induction time, and rate of crystallization. The crystal habit variables include size, shape orientation, and correlation to the template structure. In the second stage, the study will focus on the dye crystallization inside the polyelectrolyte shell. The shell will consist of polyelectrolyte multilayers permeable to small polar molecules but not their crystals. In addition to the polyelectrolytes, supported phospholipid bilayers will be used as templates because they provide intermediate order and flexibility. This project is intended as a proof-of-concept study. Future work can go beyond the generic polyelectrolytes using polymers with higher architectural definitions such as amphiphilic polymers, ionomers, and biopolymers.This research may have broader impact in terms of its relationship to the concept of nano-science and technology especially in areas such as materials processing, color displays, information storage, nanocomposites, drug encapsulation, and sensors. For example, the encapsulated colloids can be used as tips for micropipettes, as chemical sensors to detect pollutants, and as heterogeneous catalysts.Also, the support will allow the P.I. to continue exploring the molecular mechanisms in the templated growth of organic with potential applications in encapsulation, coatings, and materials processing. It will also help the P.L to establish long-term collaboration and exchanges with a foreign research institution: the Max-Planck-Institute of Colloids and Interfaces. Some experiments will be conducted at the Institute with a number of characterization methods not present at the P.I.'s home institution. The planned educational and outreach activities include incorporation of research topics into materials engineering curricula, global education associated with the World Bridge program, mentoring of Detroit high school students in the Science Summer Camp program, and training science teachers from local community colleges.