New Insights into Spin Coating of Polymer Thin Films in Both Wetting and Nonwetting Regimes
New Insights into Spin Coating of Polymer Thin Films in Both Wetting and Nonwetting Regimes
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DOI：
10.1021/acs.langmuir.2c02206
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发表时间：
2022-10-06
期刊：
影响因子：
3.9
通讯作者：
Chen, Wei
中科院分区：
文献类型：
--
作者：
Jiang, Yuxin;Minett, Margaret;Chen, Wei
旋涂是在平面基底上制造聚合物薄膜的常用方法。薄膜厚度 (h) 和旋转速率 (w) 之间已建立的 Meyerhofer 关系（h 与 w-1/2 成比例）使得可以通过调整旋转速率和其他实验参数来制备具有所需厚度的薄膜。 1/2 指数已被先前涉及在硅晶片上制备的有机薄膜的研究所验证。在这项研究中，88% 和 >99% 的水解聚（乙烯醇）（PVOH）聚合物被吸附并从水溶液中旋涂到四种不同的基材上。通过将不同分子量的聚（二甲基硅氧烷）（PDMS）共价连接到硅片（SiO2）上来制备基底。原子力显微镜图像表明，随着 PDMS 分子量的增加，PVOH 薄膜从 SiO2 上的稳定转变为亚稳态，然后转变为不稳定。值得注意的是，这里研究的聚合物-基底系统都没有表现出 Meyerhofer 模型预测的厚度-旋转速率分布。基于实验结果，提出了一个更通用的吸附沉积模型，将总旋涂厚度解耦为两个分量——吸附厚度（h1）和旋涂厚度（h2）。前者解释聚合物-基底相互作用，后者取决于聚合物浓度和旋转速率。在不稳定的系统中，发现指数类似于 0，因为在旋转过程中在溶液-基底界面处发生滑移，并且旋转沉积厚度为 0。在亚稳态和稳定系统中，出现了旋转沉积厚度和旋转速率之间的普遍关系，与所检查的每种聚合物的基底类型和聚合物浓度无关。我们的研究结果表明薄膜稳定性和聚合物-基底相互作用在旋涂应用中的重要性。
Spin coating is a common method for fabricating polymer thin films on flat substrates. The well-established Meyerhofer relationship between film thickness (h) and spin rate (w), h proportional to w-1/2, enables the preparation of thin films with desired thickness by adjusting the spin rate and other experimental parameters. The 1/2 exponent has been verified by previous studies involving organic thin films prepared on silicon wafers. In this study, 88% and >99% hydrolyzed poly(vinyl alcohol) (PVOH) polymers were adsorbed and spin-coated from an aqueous solution onto four different substrates. The substrates were prepared by covalently attaching poly(dimethylsiloxane) (PDMS) of different molecular weights onto silicon wafers (SiO2). Atomic force microscopy images indicate that the PVOH films transitioned from stable on SiO2, to metastable, and then to unstable as PDMS molecular weight was increased. Notably, none of the polymer-substrate systems studied here exhibited the thickness-spin rate profile predicted by the Meyerhofer model. Based on the experimental results, a more general adsorption-deposition model is proposed that decouples the total spin coated thickness into two components -the adsorbed thickness (h1) and the spin-deposited thickness (h2). The former accounts for polymer-substrate interactions, and the latter depends on polymer concentration and spin rate. In unstable systems, the exponents were found to be similar to 0 because slip takes place at the solution-substrate interface during spin and the spin-deposited thickness is 0. In metastable and stable systems, a universal relationship between spin-deposited thickness and spin rate emerged, independent of the substrate type and polymer concentration for each polymer examined. Our findings indicate the importance of film stability and polymer-substrate interactions in the application of spin coating.