2.1 Materials
MMT powder (the model is PGN sodium-based MMT) was purchased from Nanocor Inc., America. Its color is dark white, with an average particle size of 5 μm, and its cation exchange capacity (CEC) is 120±1.2 meq/100g. 4,4’-Diaminobenzanilide (DABA) and 4,4’-biphthalic anhydride (BPDA) were purchased from J&K Scientific Ltd., China. N, N-dimethyl acetamide (DMAc, water≤50 ppm), triethylamine (TEA, 99.5%), (3-aminopropyl) triethoxysilane (KH550, 99%), and sodium hydroxide (NaOH, 97%) were supplied by Energy Chemical Co., Ltd., China. Polyvinyl alcohol (PVA, DP ≈ 1750±50) was purchased from Sinopharm Chemical Reagent Co., Ltd., China. Carboxymethyl cellulose (CMC, M.W. = 700000) was purchased from Aladdin Biochemical Technology Co., Ltd., China. PI substrates, made by DABA and BPDA were obtained from Wu Xi Shun Xuan New Materials Co., Ltd., China, and named DABPPI. PU foam with a density of 30 kg/m3 was purchased from Langfang PU products factory, China. DABA and BPDA were dried in a vacuum oven at 80oC and 150 oC for 8 h before use, respectively. Other chemicals were used as received.