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Supporting Information
Superelastic Polyimide Nanofiber-Based Aerogels Modified with Silicone
Nanofilaments for Ultrafast Oil/Water Separation
Ying Shena, Dawei Li*a
, Lanlan Wang a, Yuqi Zhoua, Feng Liua, Huiping Wua,
Bingyao Deng*a and Qingsheng Liua
a. Key Laboratory of Eco-Textiles (Ministry of Education), Nonwoven Technology Laboratory, Jiangnan University, Wuxi 214122, China.
Corresponding Authors
Dawei Li — E-mail: [email protected]
Bingyao Deng — E-mail: [email protected]
Material
Polyimide (P84) staple fiber with a liner density of 2.2 dtex and a length of 50-80 mm was provided by Evonik (Austria) (Table S1). The chemical structure of P84 is listed as following:
The EVONIK official website lists the characteristics of P84 fibers. More information
about P84 could be found here:
https://www.p84.com/product/p84/en/pages/polyimide-fibres.aspx Table S1 Characteristics of P84 staple fiber.
Property Typical Value
Length 50-80 mm
Liner density 2.2 dtex
Tenacity 38 cN/tex
Elongation 30%
Density 1.41 g cm-3
Characterization
To determine the dimensional change of NFAs during process, the radius and height were measured using a vernier caliper before and after welding and coating, respectively. The microscopic morphologies of the PI nanofibers were investigated by scanning electron microscopy (SEM, SU1510, Corporation, Japan). To determine the length of short PI nanofibers, the dispersion was casted onto the aluminum foil and then dried in a vacuum oven. The dried nanofiber and as-prepared NFAs were sputter
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coated with gold at 20 mA for 30 s and observed by SEM with an accelerating voltage of 15 kV. The length of the short-cut nanofibers was measured based on the SEM images using ImageJ (National Institutes of Health, USA). 100 nanofibers were randomly picked for each sample. The major pore size of NFAs was also determined by measuring the perimeter of 100 major pores. Chemical elements were qualitatively analyzed by energy dispersive spectroscopy (EDS). The specific surface area (SBET) of
NFAs was tested by N2 adsorption method using a Autosorb iQ (Quantachrome
Instrument Co., USA) automatic specific area tester. The chemical compositions were analyzed by Fourier transform infrared (FT-IR) spectroscopy (Nicolet is 10, Thermo Fisher Scientific Co., Ltd, USA) in the range of 400-4000 cm-1. The size of water microspheres was determined by a Zeta potential analyzer (ZetaPlus, NanoBrook, USA).
The compression tests were performed on HY-940FS (Shanghai Yiyi Instrument Co., China) equipped with a 50-N load cell. In these tests, cylindrical sample with a diameter of ~20 mm and a thickness of ~16 mm was employed, while the compressive rate during loading and unloading was set as 3 mm min-1.
Figure S2. Photograph of the dispersion of PI nanofiber in tert-butanol (a), SEM image (b) and fiber length distribution (c) of the dispersed PI nanofibers.
Figure S1. SEM image of PI nanofibers with an average diameter of 261.48 ± 65.15 nm.
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Figure S3. (a) Photo showing the unwelded PI-NFAs. (b) SEM image of the resultant fibrous cellular architecture. (c) Compressive strain-stress curves. (d) Optical profiles of the unwelded PI-NFAs and welded PI-NFAs. (e) SEM image showing unwelded PI-NFAs without welding among fibers. (f) SEM image of welded PI-NFAs exhibited obvious welded 3D fibrous networks with strong bonding among the fibers.
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Figure S4Si elemental mapping of (a1, a2) PI-NFAs, (b1, b2) SiNFs/PI-NFA3, (c1, c2)
SiNFs/PI-NFA6, (d1, d2) SiNFs/PI-NFA12, (e1, e2) SiNFs/PI-NFA18 and (f1, f2)
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Figure S5 SEM images and EDX spectra of the external part (a1, a2, a3) and the
internal part (b1, b2, b3) of the composite SiNFs/PI-NFA18.
Figure S6 SEM images showing the hierarchical cellular structures of PI-NFAs (a), SiNFs/PI-NFA3 (b), SiNFs/PI-NFA6 (c), SiNFs/PI-NFA12 (d), SiNFs/PI-NFA18 (e)
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Figure S7 (a) N2 adsorption-desorption isotherms and (b) DFT pore size distribution
of various NFAs.
Figure S8 Absorption capacity dependence on the viscosity of liquids.
Figure S9 Log normal droplet size distribution of the surfactant-free water-in-hexane emulsion before separation.
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Figure S10 Major pore size distribution of SiNFs/PI-NFA12.
Figure S11 FT-IR spectra of SiNFs/PI-NFA12 before and after separation of
petroleum ether (a) and hexane (b) from water, and after squeezing and evaporation of petroleum ether (a) and hexane (b).
The chemical structure after separation experiment was investigated. As shown in Figure S11, the peaks at 3000 - 2800 cm-1 were characteristic asymmetric and
symmetric vibration of C-H groups of petroleum ether and n-hexane, respectively. It clearly demonstrated that the oil was captured by SiNFs/PI-NFA12 in the coalescence
selective process. After squeezing and evaporation, nearly all of the oils were removed from SiNFs/PI-NFA12.
Figure S12 SEM images of SiNFs/PI-NFA12 after circular separation.
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divided by its volume. The porosity of the aerogel was determined by the following formula: 0 0 / 100% V m p V − = (1)
where p is the apparent density of the aerogel, V0 is the volume of the cellular
materials, m is the mass of the solid constituents, and ρ is the density of solid constituents. In this work, the densities of the fiber constituents were measured based on the ISO 10119:2002 standard. In a typical case of the SiNFs/PI-NFA3 with a
density of 6.54 mg cm-3, the solid constituents in aerogels are the PI nanofibers (93.86
wt %, 1.41 g cm-3) and SiNFs (6.14 wt %, 2.2 g cm-3). Therefore, 0.006138 0.000401
1 100% 99.55%
1.41 2.2
p= − − =
（2）
Table S2 Parameters of SiNFs/PI-NFAs with different SiNFs contents. Aerogels PI-NFAs SiNFs/
PI-NFA3 SiNFs/ PI-NFA6 SiNFs/ PI-NFA12 SiNFs/ PI-NFA18 SiNFs/ PI-NFA24 SiNFs content (wt %) 0 6.14 8.34 10.31 21.53 33.78 Shrinkage (v/v, %) 0 3.28 3.45 3.96 6.63 8.60 Density (mg cm-3) 5.29 6.54 7.11 7.31 8.76 9.41 SBET (m2 g-1) 22.807 27.789 29.181 31.675 47.704 31.829 Porosity (%) 99.62 99.55 99.51 99.50 99.43 99.41 Table S3 Quant results of the Si elemental mapping of SiNFs/PI-NFAs.
NFAs Internal part (wt %) External part (wt %)
PI-NFAs 0 0 SiNFs/PI-NFA3 2.50 3.24 SiNFs/PI-NFA6 8.15 9.71 SiNFs/PI-NFA12 12.41 13.92 SiNFs/PI-NFA18 14.79 17.67 SiNFs/PI-NFA24 20.67 25.48
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Table S4 Decomposition temperature (Td), temperatures at 5% weight-loss (T5%), and
the temperature max weight-loss (Tmax) of these NFAs.
NFAs Td (oC) T5% (oC) Tmax (oC) Unwelded PI-NFAs 430 486 637 PI-NFAs 430 451 612 SiNFs/PI-NFA3 430 481 634 SiNFs/PI-NFA6 430 497 638 SiNFs/PI-NFA12 430 514 648 SiNFs/PI-NFA18 430 497 638 SiNFs/PI-NFA24 430 360 632 Movies
Water and oil droplet adhesion Movie S1.mp4
Selective absorption of SiNFs/PI-NFA12
in air Movie S2.mp4
Selective absorption of SiNFs/PI-NFA12
under water Movie S3.mp4
Effective separation of SiNFs/PI-NFA12
for layered oil/water mixtures Movie S4.mp4
Separation process of