S. Luo et al.
Polymer 218 (2021) 123522
providing a new method for preparing new oil–water separation
of nitrogen before recrystallizing with n-heptane to obtain the com-
pound 3,3′-diallyl-4,4′-biphenol (DABP). 1H NMR (600 MHz, DMSO‑d6)
δ 9.313 (m, 1H), 7.197 (m, 2H), 6.821 (m, 1H), 5.976 (m, 1H), 5.040 (m,
2H), 3.321 (m, 2H), as shown in Scheme 1.
membranes.
2. Experimental
2.1. Materials
2.4. Polymer synthesis
4,4′-dihydroxydiphenyl, potassium carbonate (K2CO3), allyl bro-
mide, octamethylcyclotetrasiloxane (D4), dimethyldichlorosilane, kar-
stedt’s catalyst solution, and 1,1,3,3-tetramethyldisiloxane (TMDS)
were purchased from Macklin Industrial Corporation, China. PVDF
(Solef 6010; Mw = 600 000 g molꢀ 1) was obtained from Solvay
Advanced Polymers L.L.C (Alpharetta, GA, USA). Kg-23 chain extender
was obtained from Mendeleyev University of Chemical Technology,
Russia. Toluene, anhydrous magnesium sulfate, magnesium sulfate
anhydrous, dimethylformamide (DMF), acetone, tetrahydrofuran (THF),
anhydrous calcium chloride, anhydrous calcium chloride, and anhy-
drous ethanol were obtained from Beijing Chemical Industry, Beijing,
China. Distilled water obtained with a laboratory water-purification
system (Smart-Q15 Shanghai Hitech Instruments Co., Ltd., China) was
used throughout. All solvents were used as received without further
purification.
TMDS, TTDS, and 2H-PDMS-10 were placed three flasks. After add-
ing excess DABP, they were heated to 110 ◦C for 10 min. Then, 50
μL of
Karstedt’s catalyst was added, and the reaction was allowed to proceed
for 10 h. To remove the toluene solvent and low-boiling-point copol-
ymer, rotary evaporation was performed. Three DABP/PDMS copolymer
samples with different segment ratios (hereafter denoted as DPn, where
n = 0, 1, and 8) were obtained, as shown in Scheme 2. 1H NMR as shown
in Fig. S1.
DP0: 1H NMR (600 MHz, DMSO‑d6) δ 9.26–9.06 (m, 1H), 7.30–7.12
(m, 2H), 6.81 (m, 1H), 2.59–2.54 (m, 2H), 1.59 (m, 2H), 0.56 (m, 2H),
0.13 to ꢀ 0.07 (m, 6H).
DP1: 1H NMR (600 MHz, Chloroform-d) δ7.37–7.23 (m, 1H), 6.96(m,
1H), 6.92–6.75 (m, 1H), 3.96 (m, 1H), 2.68 (m, 1H), 1.92–1.62 (m, 2H),
0.68 (m, 2H), 0.22 to ꢀ 0.02 (m, 9H).
DP8: 1H NMR (600 MHz, Chloroform-d) δ 7.50–7.42 (m, 1H), 6.95
(m, 1H), 6.87–6.77 (m, 1H), 2.69 (m, 2H), 1.72 (m, 2H), 0.71–0.63 (m,
2H), 0.31 to ꢀ 0.04 (m, 30H).
2.2. Characterization techniques
1H NMR spectra were obtained using a nuclear magnetic resonance
(NMR) spectrometer (Avance 600, Bruker) with CDCl3 as solvent and
tetramethylsilane as an internal reference. Fourier transform infrared
(FT-IR) spectra were obtained with an FT-IR system (Nexus 670, Nicolet)
within the range of 4000–400 cmꢀ 1 at room temperature. The samples
were mixed with KBr and pressed into flasks. The morphologies and
microspheres of the copolymer were observed with a scanning electron
microscopy (SEM, FEI XI, 30 ESEM FEG), and the elemental composition
of the copolymer membranes was characterized using and energy-
dispersive spectrometer (EDS, EDAX Genesis XM2) connected to the
SEM. Water contact angles were obtained with a Drop Shape Analyzer
2.5. Membrane fabrication
To fabricate the copolymer that was used as the scaffold for the
microsphere-coated membrane, a doping solution was prepared by
adding 10% (w/v) PVDF into the mixed solvent with DMF and acetone
(3:2, v/v), followed by stirring at room temperature for 6 h until the
polymer was dissolved completely. Electrospun membranes were ob-
tained through the accumulation of charged (16 kV) nanofibers on a
collector (12 cm from the nozzle) at a flow rate of 0.5 mL/h. To form the
surface structure of the two kinds of coated membranes with well-
shaped polymer microspheres, 2% DPn with 2% PVDF (w/v) were
mixed solvent with DMF and THF (3:2, v/v), which were electrospun to
fabricate the hierarchical membrane. The electrospinning parameters
were as follows: applied voltage of 16 kV, receiving distance of 12 cm,
and feeding rate of 0.5 mL/h. The schematic of the electrospinning de-
vice is shown in Fig. 1. Finally, the fabricated double-layer membranes
were carefully taken out of the barrel and dried in an oven at 50 ◦C for
more than 24 h. All membranes were fabricated at room temperature
with relative humidity less than 50%.
(DSA100, Kruss). Droplets of deionized water from a 4 μL syringe were
dropped perpendicularly onto the membrane surface at room tempera-
ture. Each membrane was measured five times, and the mean value was
recorded. The thermal properties of all samples were studied by DSC
(DSC, PerkinElmer). In a nitrogen atmosphere, about 3–5 mg of sample
was heated from 30 ◦C to 250 ◦C at a rate of 10 ◦C minꢀ 1. Thermogra-
vimetric measurement (TGA) was performed in dynamic mode using a
TA instrument (Q500 thermal analyzer, TA) with nitrogen atmosphere
(flow rate = 60 mL minꢀ 1). The sample was under nitrogen atmosphere
and heated from room temperature to 800 ◦C (10 ◦C minꢀ 1).
2.6. Oil–water separation
2.3. Synthesis of monomer
To measure the oil–water separation performance of PVDF/DPn
membranes, they were fixed between a glass funnel and a beaker with an
effective separation area of 4.41 cm2. To induce contact between the oil
phase and membrane, the oil–water separation equipment was placed at
an angle of 45◦, and 30 mL of n-hexane mixed with 30 mL of water was
poured into the upper glass funnel. Separation was achieved by gravity.
To ensure completed separation, the system was maintained for 5–10
min, and then two barrels were used to collect oil and water. The
calculation formula of separation efficiency was as follows:
D4, TMDS, and Kg-23 catalyst were placed in a three-neck flask, and
the reaction was heated to 80 ◦C under nitrogen atmosphere for 12 h.
After purification, the viscous, transparent oil terminated hydrogen
siloxane monomer was obtained and denoted as 2H-PDMS-10. Yield:
about 86%. 1H NMR (600 MHz, Chloroform-d) δ 4.71 (m, 2H), 0.28 to
ꢀ 0.04 (m, 60H).
TMDS, dimethyldichlorosilane, and deionized water were added,
and the solution was mixed for three days at room temperature. Then,
the crude product was neutralized, dried, and distilled under reduced
pressure. A colorless transparent liquid was obtained and denoted as
v1
v2
Φ =
(1)
1
TTDS. Yield: about 82%. As shown in Scheme 1. H NMR (600 MHz,
where ϕ is the separation efficiency, and v1 and v2 are the volume of oil
before and after separation (mL), respectively. The calculation formula
of oil–water separation flux was as follows:
Chloroform-d) δ 4.71 (m, 1H), 0.21 (m, 6H), 0.09 (m, 3H).
4,4′-Dihydroxydiphenyl, K2CO3, and bromopropene were placed in a
flask. The reaction was heated to 85 ◦C for 8 h, and then a large amount
of distilled water was added to the reaction to obtain white crystals,
which were rinsed and dried. The dried product was followed to Claisen
Rearrangement, which was heated at 205 ◦C for 2 h under the protection
V
At
Flux =
(2)
2