Micro/Nano-patterning of Thin Polymer Films

发展不依赖于传统刻蚀技术的、图案尺寸等可以动态调控的微图案化方法是当前国际上的研究热点。高分子由于可以通过可控聚合调控其预定结构和尺寸，并且具有易于加工和可以嵌入多种化学功能团等特点，是制备不依赖于传统刻蚀技术的价廉、高产的微图案化的理想材料。因而设计具有特定结构的高分子，利用高分子的丰富的相态结构和其在外场等作用下的性质，发展高分子图案化方法、技术和原理具有重要意义。本论文利用高分子的尺度和结构特征以及对外场的响应特性，研究其自组装形成微、纳米图案的影响因素和机理，掌握了调控图案形态、尺寸、表面性质的规律，实现了稳定、有序的智能图案的动态设计。主要内容如下：（1）利用冷凝的水蒸汽液滴为模板，在PS、PMMA等均聚物薄膜上制备了微米尺寸的规则孔洞结构。研究了溶剂性质、聚合物溶液粘度、环境湿度等对规则孔洞形成的影响，观察了孔洞形成的中间过程，提出了孔洞形成的机理。（2）研究了高分子均聚物和以聚合物为基体的发光小分子薄膜在外场（电场、温度场）作用下的长程有序规则排列图案的形成条件和机理，以及外场作用对高分子有序结构的影响因素。静电力和温度梯度使薄膜变得不稳定，表面产生具有一定波长和周期的起伏波，这种波动逐渐增强使薄膜破裂最终形成规则结构。（3）通过研究发现薄膜厚度、溶剂对不同链段的选择性以及溶剂蒸汽处理时间对嵌段共聚物薄膜表面形态的演变有重要影响。对于对称双嵌段共聚物PS-b-PMMA薄膜，在PMMA的选择性溶剂蒸汽中，通过改变溶剂蒸汽对PS-b-PMMA薄膜的溶胀程度和处理时间，得到规则孔洞到条纹转变的一系列纳米结构和规则小球到条纹转变的一系列纳米结构。溶剂蒸汽改变了薄膜边界条件，使富集在基底的PMMA向薄膜表面迁移，使其表面形貌和组成发生变化。通过将此体系与均聚物和短链嵌段共聚物共混，改变链段间的界面张力，可以调控纳米结构的尺寸。更进一步，得到的纳米结构图案化的薄膜具有环境敏感性。当将其置于对PS嵌段具有选择性的溶剂蒸汽中时，变换薄膜的边界条件，表面形貌和性质发生了反转。The fabrication, characterization and manipulation of micro/nano-systems bring together physics, chemistry, materials science and biology in an unprecedented way. The ability to fabricate micro/nanostructures by non-conventional method is essential in the future development of functional devices that incorporates micro/nanoscale features. In this respect, polymers are potentially ideal micro/nanoscale building blocks because of their natural length scale, well-defined architecture, controlled synthesis, ease of processing and wide range of chemical functionality that can be incorporated. In this thesis, we investigated the mechanisms to pattern polymer surfaces at different length scales. The chemical and physical properties of the nanostructured surfaces have been studied. Main contents are as follows: . (1) By water droplet templating, micrometer scale regular holes are prepared in PS> PMMA thin films. The influences of solvent properties, polymer molecular weight, and the humidity of atmosphere on the pattern formation are investigated. The formation mechanism of regular holes is proposed. (2) We research the formation condition and mechanism of long-range ordered patterns in homopolymer and polymer-based photo luminescent material thin films under external fields (electric field-, temperature gradient field). Electrostatic force and temperature gradient destabilize the polymer film and induce the fluctuation on the surface, which can be further amplified and result in regular patterns in the film. (3) We investigate the time development of the microdomain structure in symmetric diblock copolymer PS-b-PMMA thin films via PMMA-selective solvent vapor treatment. By varying the swelling degree of PS-b-PMMA thin films and annealing time, a series of nanostructures developing from highly ordered nanoscale depressions to stripes or from highly ordered nanoscale spheres to stripes can be obtained. Solvent vapor changes film boundary condition, attracts the PMMA-rich layer at the substrate upward, and changes the surface morphology and component. By blending the system with homopolymers and short-chain block copolymer, the interfacial tension between the two blocks is changed and the size of nanostructures can be controlled. Furthermore, The resulted nanostructures turn out to be sensitive to environmental stimuli. By switching the film boundary condition to PS-selective solvent vapor, their morphologies and surface properties can be reversibly switchable