Influence of Ionomer Loading and Substrate Wettability on the Morphology of Ionomer Thin Films Using Coarse-Grained Solvent Evaporation Simulations,Macromolecules

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Influence of Ionomer Loading and Substrate Wettability on the Morphology of Ionomer Thin Films Using Coarse-Grained Solvent Evaporation Simulations
Macromolecules ( IF 5.1 ) Pub Date : 2020-12-28 , DOI: 10.1021/acs.macromol.0c01303
Takuya Mabuchi _{1,

2} , Sheng-Feng Huang ₂ , Takashi Tokumasu ₂

Affiliation

Coarse-grained molecular dynamics simulations were performed to understand the evolution of ionomer morphologies in solutions during solvent evaporation. To reproduce experimental fabrication conditions, the simulation conditions, such as evaporation and sedimentation rate, were determined based on a dimensionless parameter, the Péclet number, providing a direct link between simulation results and experimental findings. The effects of ionomer loading and substrate wettability on the morphologies of ionomer thin films after drying were investigated extensively, which exhibit similar trends reported in experiments. At low ionomer loading, a discontinuous patchy film with a minimum thickness of ≈3 nm was formed on the hydrophobic substrate, whereas a high-coverage continuous film of ≈2 nm thickness was found on the hydrophilic substrate. At high ionomer loading, regardless of the substrate wettability, a lamellar-like morphology with multiple water-rich layers was observed, although the stability of the layer structures and the ionomer surface roughness differ between the substrate types because the substrate wettability strongly affects the adsorption behaviors of ionomers and water as the first layer in the interfacial region. Our findings of a decrease in the degree of phase segregation with increasing thickness suggest an eventual collapse of the lamellar structure at a certain thickness within a few tens of nanometers or even thinner.

中文翻译：

粗粒溶剂蒸发模拟对离聚物负载量和底物润湿性对离聚物薄膜形貌的影响

进行了粗粒度的分子动力学模拟，以了解溶剂蒸发过程中溶液中离聚物形态的演变。为了重现实验制造条件，基于无量纲参数Péclet数确定了模拟条件，例如蒸发和沉降速率，从而提供了模拟结果与实验结果之间的直接联系。广泛研究了离聚物负载量和基质润湿性对干燥后离聚物薄膜形态的影响，在实验中也显示出相似的趋势。在低离聚物负载下，在疏水性基材上形成了最小厚度约为≈3nm的不连续膜，而在亲水性基材上却发现了厚度约为≈2nm的高覆盖率连续膜。在高离聚物负载下，无论基质的可湿性如何，均会观察到具有多个富水层的层状形态，尽管基质类型之间的层结构稳定性和离聚物表面粗糙度有所不同，因为基质的可湿性会严重影响吸附离子聚合物和水作为界面区域第一层的行为我们发现，随着厚度的增加，相偏析程度降低，这表明层状结构最终会在几十纳米甚至更薄的厚度范围内坍塌。尽管在基材类型之间层结构的稳定性和离聚物表面粗糙度是不同的，因为基材的润湿性强烈影响作为界面区域中第一层的离聚物和水的吸附行为。我们发现，随着厚度的增加，相偏析程度降低，这表明层状结构最终会在几十纳米甚至更薄的厚度范围内坍塌。尽管在基材类型之间层结构的稳定性和离聚物表面粗糙度是不同的，因为基材的润湿性强烈影响作为界面区域中第一层的离聚物和水的吸附行为。我们发现随着厚度的增加，相偏析程度降低，这表明层状结构最终会在数十纳米甚至更薄的厚度范围内坍塌。

更新日期：2021-01-12

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