Leniart Arkadiusz A, Pula Przemyslaw, Tsai Esther H R, Majewski Pawel W
Department of Chemistry, University of Warsaw, Warsaw 02089, Poland.
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
Macromolecules. 2020 Dec 22;53(24):11178-11189. doi: 10.1021/acs.macromol.0c02026. Epub 2020 Dec 1.
We report a facile method of ordering block copolymer (BCP) morphologies in which the conventional two-step casting and annealing steps are replaced by a single-step process where microphase separation and grain coarsening are seamlessly integrated within the casting protocol. This is achieved by slowing down solvent evaporation during casting by introducing a nonvolatile solvent into the BCP casting solution that effectively prolongs the duration of the grain-growth phase. We demonstrate the utility of this solvent evaporation annealing (SEA) method by producing well-ordered large-molecular-weight BCP thin films in a total processing time shorter than 3 min without resorting to any extra laboratory equipment other than a basic casting device, ., spin- or blade-coater. By analyzing the morphologies of the quenched samples, we identify a relatively narrow range of polymer concentration in the wet film, just above the order-disorder concentration, to be critical for obtaining large-grained morphologies. This finding is corroborated by the analysis of the grain-growth kinetics of horizontally oriented cylindrical domains where relatively large growth exponents (1/2) are observed, indicative of a more rapid defect-annihilation mechanism in the concentrated BCP solution than in thermally annealed BCP melts. Furthermore, the analysis of temperature-resolved kinetics data allows us to calculate the Arrhenius activation energy of the grain coarsening in this one-step BCP ordering process.
我们报道了一种排列嵌段共聚物（BCP）形态的简便方法，其中传统的两步浇铸和退火步骤被一步法所取代，在该一步法中，微相分离和晶粒粗化在浇铸过程中无缝整合。这是通过在浇铸过程中引入非挥发性溶剂来减缓溶剂蒸发实现的，该非挥发性溶剂有效地延长了晶粒生长阶段的持续时间。我们通过在总处理时间短于3分钟的情况下制备出有序的大分子量BCP薄膜，证明了这种溶剂蒸发退火（SEA）方法的实用性，除了基本的浇铸设备（如旋涂或刮涂器）外，无需任何额外的实验室设备。通过分析淬火样品的形态，我们确定湿膜中聚合物浓度在略高于有序-无序浓度的相对较窄范围内，对于获得大晶粒形态至关重要。对水平取向圆柱状畴的晶粒生长动力学分析证实了这一发现，其中观察到相对较大的生长指数（1/2），这表明在浓BCP溶液中缺陷湮灭机制比在热退火BCP熔体中更快。此外，对温度分辨动力学数据的分析使我们能够计算出这种一步法BCP排列过程中晶粒粗化的阿仑尼乌斯活化能。
