Chen Xia-Chao, Ren Ke-Feng, Chen Jia-Yan, Wang Jing, Zhang He, Ji Jian
MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, China.
Phys Chem Chem Phys. 2016 Nov 16;18(45):31168-31174. doi: 10.1039/c6cp05419f.
Introducing wrinkling or rough features into substrates is of great practical significance to construct various functional surfaces. Due to the sensitivity of assembled units towards environmental stimuli, the internals of layer-by-layer films can be readily adjusted to generate various micro- and nanostructures. We previously described a self-roughening polyelectrolyte multilayer (PEM) to facilitate the introduction of surface microstructures. In the present work, the growth process of PEI/PAA multilayer films was investigated and the mean size of the surface microstructures was found to increase linearly with the film thickness. The spontaneous formation of these surface features can be attributed to swelling-induced film deformation during the assembling process, which is similar to the surface wrinkling of hydrogels undergoing a volume phase transition. When exposed to saturated humidity, the internal stress as well as the surface microstructures can be diminished spontaneously, leading to a flat surface over the substrates. Given the effect of the underlying film thickness on the characteristic wavelength of the surface wrinkles, multiscale surface microstructures can be readily realized by means of spatially presetting the distribution of the film thickness.
在基底中引入皱纹或粗糙特征对于构建各种功能表面具有重要的实际意义。由于组装单元对环境刺激的敏感性，层层薄膜的内部结构可以很容易地进行调整以产生各种微纳结构。我们之前描述了一种自粗糙化聚电解质多层膜（PEM），以促进表面微结构的引入。在本工作中，研究了PEI/PAA多层膜的生长过程，发现表面微结构的平均尺寸随膜厚度呈线性增加。这些表面特征的自发形成可归因于组装过程中溶胀诱导的膜变形，这类似于经历体积相变的水凝胶的表面皱纹。当暴露于饱和湿度时，内部应力以及表面微结构会自发减小，从而使基底表面变平。考虑到底层膜厚度对表面皱纹特征波长的影响，通过空间预设膜厚度的分布可以很容易地实现多尺度表面微结构。
