Supporting Information: Bio-inspired Hierarchical Macromolecule-nanoclay Hydrogels. for Robust Underwater Superoleophobicity

Transcription

1 Supporting Information: Bio-inspired Hierarchical Macromolecule-nanoclay Hydrogels for Robust Underwater Superoleophobicity By Ling Lin, 1,3 Mingjie Li, 2,3 Li Chen, 1,3 Peipei Chen, 2,3 Jie Ma, 1 Dong Han, 2 * Lei Jiang 1 * 1. Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Organic Solids, Institute of Chemistry Chinese Academy of Sciences, Beijing , P. R. China 2. National Center for Nanoscience and Technology, Beijing , China 3. Graduate University of Chinese Academy of Sciences, Beijing, , P. R. China To whom correspondence should be addressed: jianglei@iccas.ac.cn, dhan@nanoctr.cn 1

2 Figure S1 Figure S1. Oil static contact angles (CAs) on different hydrogel surfaces with increasing C clay. Red curve represents bio-inspired hierarchical surfaces, while black curve represents smooth surfaces. By constructing hierarchical surfaces, hydrogels achieve superoleophobicity. Figure S2 Figure S2. Oil static contact angles (CAs) on different C-hydrogel surfaces using n-decane as the detecting oil. Substrate (S) = hydrogel, Liquid (L) = n-decane, Medium = water (W). a) Smooth surface shows oleophobicity with an oil CA of 144.5±1.4. b) Hierarchically micro- /nanostructured surface exhibits superoleophobicity with an oil CA of 156.2±1.6. The results confirm that hydrogels with hierarchical surfaces show superoleophobicity to different oils. 2

3 Figure S3 Figure S3. Compressive properties of as-prepared traditional PNIPAAm hydrogels (Thydrogels) with different cross-linking density (chemically cross-linked by BIS). a) Stressstain curves of T-hydrogels. As the cross-linking density decreases, strain at fracture increases. b) The compressive modulus enhances with the increase of cross-linking density, calculated from the slope of initial liner area (10-20%). Compared with C-hydrogels, T- hydrogels possess low modulus and stress, which are limited for the applications. 3

4 Figure S4 Figure S4. Tensile properties of hybrid PNIPAAm-nanoclay hydrogels (C-hydrogels). a) Photographs of C- hydrgel during a tensile test. C-hydrogel can be elongated extremely, while T-hydrogel is too fragile to be applied in our experiments. b) Stress-stain curves of C- hydrogels with different clay content. The tensile strength enhances with increasing C clay, without sacrificing most of the extensibility. c) The tensile modulus of C- hydrogels increases monotonically with increasing C clay. The modulus was calculated from the slope of initial liner area (20-50%). 4

5 Figure S5 Figure S5. Dynamic underwater oil-adhesion measurements on hydrogel surfaces with different preloads (3 µl n-decane droplet as the detecting oil). a) Statistical histogram of the adhesion forces on smooth and hierarchical surfaces with increasing C clay. On hierarchical surfaces, oil adhesion is largely reduced when no preload appears. b) Statistical histogram of the adhesion forces on hierarchical surfaces with increasing C clay, when different preloads are performed. High clay content hydrogel shows robust ultra-low affinity to the oil. 5

6 Figure S6 Figure S6. The approach force curves of AFM on hydrogel surfaces with different clay content. a) The small value of force curve slope on T-hydrogel surface indicates the low surface mechanical strength. The sharp slope of force curve on C-hydrogel surface shows high surface mechanical strength. b) Statistical values of approach slopes on different clay content hydrogels. 6

7 Figure S7 Figure S7. Energy dispersive spectroscopy (EDS) images of the element distribution on the surface of different C-hydrogels, in which C belongs to PNIPAAm, Si and Mg belong to the clay. a) Surface element distribution of low clay content hydrogel (C-05). b) Surface element distribution of high clay content hydrogel (C-25). With the increase of clay content (from C- 05 to C-25), the amount of Si and Mg increases while the amount of C decreases, indicating the increased proportion of clay on the surface. 7

8 Figure S8 Figure S8 Transmission electron micrograph (TEM) images of ultrathin films of dried C- hydrogels at a magnification of a) Low clay content hydrogel (C-05). b) High clay content hydrogel (C-25). It is found that the clay is substantially exfoliated and dispersed homogeneously throughout the polymer matrix. With the increase of clay content (from C-05 to C-25), the number of exfoliated clay sheets largely increases. The arrows point at the exfoliated clay sheets. 8