Organic Crystal Growth on Flexible Templates

灵活模板上的有机晶体生长

• 批准号: 0221586
• 负责人: Guangzhao Mao
• 金额: $ 22.36万
• 依托单位: Wayne State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2007-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0221586&HistoricalAwards=false
• 关键词: Organic; Crystal; Growth; Flexible; Templates

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.

毛光召，韦恩州立大学“柔性模板上的有机晶体生长”这个项目将探索使用聚合物模板控制和限制有机晶体形态的可能性。用原子力显微镜等原位方法研究了模型有机染料在二维(2-D)聚电解质模板和三维(3-D)聚电解质壳层中的成核和结晶过程。这项研究的目的是(1)了解聚电解质对有机结晶的影响；(2)将有机晶体包裹在聚电解质外壳中。本研究探索了聚电解质表面结构与新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浓缩、几何和立体化学匹配、特定的相互作用和吸附诱导的稳定来发挥模板效应。聚合物衬底与无机模板的不同之处在于，它们没有显示出外延机制中所隐含的有序性和刚性。然而，众所周知，天然聚合物可以诱导出与没有聚合物生长的晶体不同的统一习性的晶体。生物矿化研究表明，聚电解质的模板效应不需要与无机电解质相同程度的几何匹配。聚电解质由于其众多的表面构象，可能表现出丰富的立体化学控制。对于给定的晶面，可能存在多个几何匹配。伸入溶液中的链段可以稳定新生晶体的侧面。在此基础上，采用以实验为主，结合Cerius2程序的方法，研究聚电解质模板与初生染料晶体之间的界面结构。最初的实验将集中在染料在二维薄膜上的结晶，以便在分子尺度上探索动力学和结晶习性的改变。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，将重点研究聚电解质壳层内的染料结晶。壳层将由聚电解质多层组成，可以渗透到小的极性分子，但不能渗透到它们的晶体。除了聚电解质之外，支撑的磷脂双层将被用作模板，因为它们提供了中间有序和灵活性。本项目旨在作为概念验证研究。未来的工作可以超越普通的聚电解质，使用具有更高结构定义的聚合物，如两亲性聚合物、离聚体和生物聚合物。这项研究可能会在其与纳米科学和技术概念的关系方面产生更广泛的影响，特别是在材料加工、彩色显示器、信息存储、纳米复合材料、药物封装和传感器等领域。例如，被包裹的胶体可以用作微吸管的尖端，用作检测污染物的化学传感器，以及作为多相催化剂。此外，这种载体还将使P.I.继续探索有机物模板化生长的分子机制，在封装、涂层和材料加工方面具有潜在的应用。它还将有助于菲律宾与一家外国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。一些实验将在该研究所进行，其中一些表征方法是P.I.S的母校没有的。计划中的教育和推广活动包括将研究主题纳入材料工程课程，与世界桥项目相关的全球教育，在科学夏令营项目中指导底特律高中生，以及培训当地社区大学的科学教师。