Ordered Block Copolymer Thin Films Studied by Guided-Wave Depolarized Light Scattering

技术说明本提案寻求资金以继续开发用于表征光学透明嵌段共聚物薄膜中各向异性纳米结构（例如层状和圆柱体）的组织的新型分析技术。从燃料电池到光电器件，纳米技术的许多应用都需要对纳米组织进行定量测量。GWDLS允许低成本、非破坏性、实时测量光学透明薄膜中的有序形成和缺陷密度。在薄膜表征方法中，GWDLS的独特之处在于它提供了薄膜中宏观长度尺度（~1 cm）上缺陷密度的平均测量。用于研究缺陷结构的位置空间方法，如原子力显微镜（AFM）和扫描电子显微镜（SEM），可以测量局部缺陷结构，但对于获得宏观区域的统计平均值是不切实际的. GWDLS技术涉及激光束耦合到由沉积在低折射率衬底上的嵌段共聚物膜组成的平面光波导的导模中。耦合到导模的光通过全内反射传播通过薄膜。当光与薄膜中的各向异性颗粒相互作用时，它产生退偏散射光，该散射光以正交偏振的导模传播。该散射光被耦合出膜并被检测。本论文的主要工作是：（1）对现有的GWDLS装置进行改造，利用光栅耦合器研究偏振光在对称的二氧化硅-聚合物-二氧化硅样品环境中的传播。(2)建立了一个理论模型，用于量化薄膜中随机取向和部分取向晶粒的GWDLS信号与统计特性之间的关系。(3)用GWDLS方法测定了具有层状和柱状结构的嵌段共聚物薄膜的有序-无序转变温度。（4）测量薄膜从无序到有序状态淬火后有序形成的动力学。(5)通过将测量信号与理论预测进行比较，获得平均晶粒尺寸的定量测量。项目所需的所有聚合物和基质将由学生准备。将使用AFM、SEM和SIMS等互补技术对薄膜进行完整的表征。 非技术性解释Balsara将担任数学和科学暑期学院的教师，该学院将大约60名来自当地高中的学生带到大学校园参加为期六周的数学和科学充实课程。通常一半的参与者是非洲裔美国人，四分之一的奇卡诺人，剩下的四分之一是亚洲人，高加索人，菲律宾人和拉丁美洲人。Garetz将继续他在理工大学大卫帕卡德技术和教育联盟中心的7年工作。他的活动包括在纽约城市科学/技术论坛上举办研讨会，来自纽约市公立学校的500名学生来到保利参加全天课程，在那里他们会见了代表高等教育中心、医院和公司的杰出工程师和技术专家。从事该项目的研究生将接受多学科的科学培训，包括聚合物、光学、光刻和非平衡热力学的合成和表征。他们在表征和操纵纳米结构薄膜方面的背景与当前和未来的技术有关。

TECHNICAL EXPLANATIONThis proposal seeks funds to continue the development of a novel analytical technique forcharacterizing the organization of anisotropic nanostructures (e.g. lamellae and cylinders)in optically transparent block copolymer thin films. Quantitative measurement oforganization is critical for many proposed applications of nanotechnology, ranging fromfuel cells to optoelectronic devices. GWDLS allows the low-cost, non-destructive, realtimemeasurement of order formation and defect density in optically transparent thinfilms. Among methods for thin-film characterization, GWDLS is unique in that itprovides an average measure of defect density over macroscopic length scales (~1 cm) ina film. Position-space methods for studying defect structure, such as atomic forcemicroscopy (AFM) and scanning electron microscopy (SEM), can measure local defectstructure, but are impractical for obtaining statistical averages over macroscopic regions.The GWDLS technique involves the coupling of a laser beam into a guided mode of aplanar optical waveguide consisting of a block copolymer film deposited on a lowrefractive index substrate. Light coupled into a guided mode propagates through the filmby total internal reflection. As the light interacts with anisotropic grains in the film, itgenerates depolarized scattered light which propagates in guided modes with orthogonalpolarization. This scattered light is coupled out of the film and detected. In the proposedwork, we will (1) Modify the current GWDLS apparatus to study the propagation ofpolarized light in a symmetric silica-polymer-silica sample environment using a gratingcoupler. (2) Develop a theoretical model for quantifying the relationship between theGWDLS signal and statistical properties of randomly oriented and partially orientedgrains in thin films. (3) Use GWDLS to determine the order-disorder transitiontemperature of block copolymer thin films with both lamellar and cylindrical order. (4)Measure the kinetics of order formation in thin films after quenching from the disorderedto the ordered state. (5) Obtain a quantitative measure of the average grain size bycomparing the measured signal with theoretical predictions. All of the polymers andsubstrates required for the project will be prepared by the students. Completecharacterization of the films using complementary techniques such as AFM, SEM, andSIMS will be carried out. NON-TECHNICAL EXPLANATIONBalsara will serve as a faculty instructor in the Math and Science Summer Academywhich brings approximately 60 students from local high schools to the University campusto participate in a six-week enrichment program in math and science. Typically half ofthe participants are African American, one quarter Chicano, and the remaining quarterAsian, Caucasian, Filipino and Latino. Garetz will continue his 7-year involvement withPolytechnic University's David Packard Center for Technology and EducationalAlliances. His activities include conducting workshops at the New York CityScience/Technology Forum where 500 students from New York City public schoolscome to Poly for a full-day program where they meet outstanding engineers andtechnologists representing centers of higher education, hospitals, and corporations. Thegraduate students working on this project will receive multidisciplinary scientific trainingencompassing synthesis and characterization of polymers, optics, lithography, and nonequilibriumthermodynamics. Their background in characterization and manipulatingnanostructured thin films is relevant for current and future technologies.