2.2 Materials synthesis
Preparation of MMT nanosheets. Put 6.0 g MMT and 500 mL deionized
water in a beaker and sonicate for 1 h. After that, a yellow turbidity
dispersion was obtained. Separate the precipitation with a centrifuge
(9000 rpm, 5 min) and collect the transparent solution MMT nanosheet
colloid. Finally, the colloid was concentrated by a rotary evaporator at
a concentration of 3.2 wt%.
Preparation of PAAS solution. First, the PAA solution was
obtained by condensation polymerization of BPDA and DABA (molar ratio of
100:99.5) in DMAc (10 wt% solid content) at 5 oC for
12 h. KH550 was then added and stirred for 3 h (KH550: BPDA was 0.01:1).
Last, the PAAS solution was prepared by adding TEA (2.0 mol equivalent
to BPDA) to the mixture at room temperature and stirring for 4 h.
Surface treatment of PI substrate. The method was to cover one
side of the DABPPI with 25 wt% NaOH solution for 25 min and then wash
it thoroughly and dry it.
Preparation of the bioinspired polyimide composite film. A
certain amount of MMT colloid was put into a three-neck flask and
diluted to 2 wt% with deionized water. Subsequently, PAAS solution was
added slowly with gentle agitation (the mass ratio of MMT to PAAS was
1:1). After continuous stirring for 4 h, uniform glue was obtained. The
surface-treated PI was sandwiched on the flange ring, and the composite
glue (20 mL) was poured onto the PI. The flange ring was placed in an
oven and set the heating program to 50 ℃/4 h, 100 ℃/1 h, 150 ℃/1 h, and
220 ℃/1 h. Finally, the bioinspired polyimide composite film was gained
and named MMT-PI.
Preparation of the bioinspired MMT film, MMT-PVA, and MMT-CMC.The specific preparation steps can be seen in Supporting
Information .
Preparation of the coated PU foam. The PU foam was cut into 10
cm×10 cm×1 cm and then dipped in the MMT-PAAS solution for 10 min. The
coated PU foam was placed in an oven and set the heating program to 50
℃/4 h, 80 ℃/1 h. The coated PU foam was named MMT/PAAS-PU.