摘要
Thin films of block copolymers （BCPs） are widely accepted as potentially important materials in a host of technological applications including nano- lithography. In order to induce domain separation and form well-defined structural arrangements, many of these are solvent-annealed （i.e. solvent swollen） at moderate temperatures. The use of solvents can be challenging in industry from an environmental point of view as well as having practical/cost issues. However, a simple and environmentally friendly alternative to solvo-thermal annealing for the periodically ordered nanoscale phase separated structures is described herein. Various asymmetric polystyrene-b-poly（ethylene oxide） （PS-b-PEO） thin films were annealed in a compressible fluid, supercritical carbon dioxide （scCO2）, to control nanodomain orientation and surface morphologies. For the first time, periodic well defined, hexagonally ordered films with sub-25 nm pitch size were demonstrated using a supercritical fluid （SCF） process at low temperatures and pressures. Predominant swelling of PEO domains in scCO2 induces nanophase separation, scCO2 serves as green alternative to the conventional organic solvents for the phase segregation of BCPs with complete elimination of any residual solvent in the patterned film. The depressurization rate of scCO2 following annealing was found to affect the morphology of the films. The supercritical annealing conditions could be used to define nanoporous analogues of the microphase separated films without additional processing, providing a one-step route to membrane like structures without affecting the ordered surface phase segregated structure. An understanding of the BCP self- assembly mechanism can be realized in terms of the deviation in glass transition temperature, melting point, viscosity, interaction parameter and volume fraction of the constituent blocks in the scCO2 environment.
块共聚物 BCP 的薄电影广泛地在大量工艺的应用包括 nanolithography 作为潜在地重要的材料被接受。以便导致领域分离并且形成明确的结构的安排，这些中的许多是退火溶剂的即在中等温度肿的溶剂。溶剂的使用能在从象有 practical/cost 问题一样的一个环境观点的工业是挑战性的。然而，为周期性地订的 nanoscale 阶段的 solvo 热的退火的一种简单、环境地友好的选择分开了结构此处被描述。各种各样的不对称的 polystyrene-b-polyethylene 氧化物 PS-b-PEO 薄电影在可压缩的液体被退火， supercritical 二氧化碳 scCO < 潜水艇 class= “ a-plus-plus ” > 控制 nanodomain 取向和表面形态学的 2 </sub>, 。第一次，有 sub-25 nm 沥青尺寸的周期的明确的、六角形地订的电影在低温度和压力用一个 supercritical 液体 SCF 过程被表明。在 scCO 的 PEO 领域的占优势的胀大 < 潜水艇 class= “ a-plus-plus ” > 2 </sub> 导致 nanophase 分离。scCO < 潜水艇 class= “ a-plus-plus ” > 2 </sub> 在有图案的电影与任何剩余溶剂的完全的消除为 BCP 的阶段分离用作对常规器官的溶剂其他的绿色。scCO 的 depressurization 率 < 潜水艇 class= “ a-plus-plus ” > 退火的 2 </sub> 追随者被发现影响这些电影的形态学。退火调节的 supercritical 能被用来定义没有另外的处理， microphase 的 nanoporous 类似物分开了电影，如同没有影响订的表面的结构分阶段执行分离结构，提供一条一步舞线路给膜。BCP 的理解自己组装机制能在 scCO 在玻璃转变温度，融化的点，粘性，相互作用参数和成分块的卷部分以偏差被认识到 < 潜水艇 class= “ a-plus-plus ” > 2 </sub> 环境。
