Light Driven Transport and Mechanistic Aspects of Relief Structure Formation in Azopolymer Films

这项研究的主要目的是进一步系统地研究偶氮功能化聚合物薄膜中的光驱动聚合物传质这一新现象，在中等光强和大大低于其玻璃化转变温度的情况下。在偶氮苯功能化聚合物薄膜上实现了大调制深度(6000A)表面浮雕光栅(SRG)的全光全息制作，无需任何前、后处理。对各种偶氮苯功能化聚合物体系中这种新颖的光驱动表面变形和SRG形成过程的系统研究已经建立了一些重要的研究成果和结论。这包括对这种全光学过程的基本理解、机理和确定可能的器件应用。该过程是通过光场梯度进行聚合物质量传输的结果，并且在聚合物膜表面启动。已经提出了一些驱动力的模型和机制。由PI建立的梯度力模型描述了在无定形偶氮苯聚合物薄膜中观察到的这种独特的光加工过程中的宏观行为。该模型利用单一的粘弹性参数，提供了进一步将实验建立的变形行为与分子水平过程和分子结构细节联系起来的机会。通过研究在选定的写入条件下定制大分子的SRG过程，可以将光塑化变形层的粘弹性参数与分子结构细节关联起来，重点进一步探索在先前的NSF资助下发现的异常的光驱动输运现象。在这种全光学过程中，几乎所有具有偶氮官能化的聚合物都可以在中等光强下进行所需的微细和非光学掺杂，而不需要任何后处理。了解这类材料中的基本光物理过程可能会导致光子技术的重要器件和制造工艺。直接刻写所需的图案有望成为课堂上使用这种不寻常的光学和聚合物物理现象进行简单而戏剧性的演示和学习的工具。

The principal objective of the proposed research is to further the systematic investigation of the novel phenomenon of photodriven polymer mass transport in azo functionalized polymer films, at modest light intensities and substantially below their glass transition temperatures. All-optical holographic fabrication of large modulation depth (6000A) surface relief gratings (SRG) have been achieved on azobenzene-functionalized polymer films, without any pre- and/or post-processing. A systematic investigation of this novel photodriven surface deformation and SRG formation process in a variety of azobenzene functionalized polymer systems has established a number of critical research findings and conclusions. This includes the fundamental understanding, the mechanism and identifying possible device applications of this all-optical process. The process is a result of polymer mass transport by optical field gradients and is initiated at the polymer film surface. A number of models and mechanisms for the driving force have proposed. The gradient force model developed by the PI describes the macroscopic behavior observed in this unique photofabrication process in amorphous azobenzene polymer film. This model utilizing a single viscoelastic parameter has presented the opportunity to further connect the experimentally established deformation behavior to molecular level processes and molecular structural details. The viscoelastic parameter of the photoplasticized deformation layer can be correlated with the molecular structural details by investigating the SRG process in tailored macromolecules under selected writing conditions.The focus of this further explore the unusual light-driven transport phenomenon discovered under prior NSF funding. In this all-optical process, desired micro and nonopatterning may be carried out in practically all polymers with some azo functionalization, at modest light intensities without any post processing. Understanding the fundamental photophysical processes in this class of materials may lead to important devices and fabrication processes for photonic technologies. Direct inscription of desired patterns is expected to serve as a simple and dramatic demonstration and learning tool for the classroom using this unusual optical and polymer-physical phenomenon.