Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843, USA.
ACS Appl Mater Interfaces. 2009 Oct;1(10):2338-47. doi: 10.1021/am900484q.
Thin composite films of branched polyethylenimine (BPEI) and Laponite clay platelets were prepared using layer-by-layer assembly. The film thickness was tailored by altering the pH of the aqueous mixtures used to deposit these films, resulting in growth that ranged from 0.5 to 5 nm/bilayer (BL). High-pH BPEI and low-pH clay produced the thickest films. The microstructure of tilted Laponite clay platelet stacks is observed with transmission electron microscopy when using unadjusted BPEI (pH 10.3) and pH 6 Laponite. This recipe resulted in a film with 83 wt % clay and a hardness of 0.5 GPa. In all films, the clay platelets are uniformly deposited and look analogous to a cobblestone path in atomic force microscopy surface images. Several 40-BL films, with thicknesses of 100 nm or more, exhibit reduced moduli ranging from 7 to 10 GPa and hardness of around 0.5 GPa, suggesting that these transparent films could be useful as hard coatings for plastic films. These thin coatings were also deposited onto cotton fabric. Each individual cotton fiber was uniformly coated, and the fabric has significantly more char left after burning than the uncoated fabric. Thermogravimetric analysis results reveal that fabric coated with 10 BLs of BPEI/Laponite produces up to 6 wt % char at 500 degrees C, which is almost 1 order of magnitude greater than that of untreated fabric. This initial study demonstrates that polymer/clay assemblies could improve the thermal stability of cotton and may be useful for fire safety applications.
使用层层自组装技术制备了支化聚乙烯亚胺（BPEI）和锂皂石纳米片的复合薄膜。通过改变用于沉积这些薄膜的水混合物的 pH 值来调整薄膜的厚度，导致生长范围从 0.5 到 5nm/双层（BL）。高 pH 值的 BPEI 和低 pH 值的粘土产生了最厚的薄膜。当使用未经调整的 BPEI（pH 10.3）和 pH 6 锂皂石时，通过透射电子显微镜观察到倾斜的锂皂石纳米片层堆的微观结构。该配方得到的薄膜中含有 83wt%的粘土，硬度为 0.5GPa。在所有的薄膜中，粘土薄片均匀地沉积，在原子力显微镜的表面图像中类似于鹅卵石路径。几个 40-BL 薄膜，厚度为 100nm 或更厚，表现出的弹性模量范围从 7 到 10GPa，硬度约为 0.5GPa，这表明这些透明薄膜可以用作塑料薄膜的硬涂层。这些薄膜也被沉积到棉织物上。每根单独的棉纤维都被均匀地覆盖，并且燃烧后残留的烧焦物比未涂层的织物明显更多。热重分析结果表明，用 10 层 BPEI/锂皂石涂层的织物在 500°C 时可产生高达 6wt%的烧焦物，这几乎比未处理的织物高一个数量级。这项初步研究表明，聚合物/粘土组装体可以提高棉织物的热稳定性，并且可能对消防安全应用有用。
