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Thermosetting polyimide (PI) foams (PIFs) are usually synthesized through chemical foaming; however, this approach is environmentally toxic, and it is difficult to regulate the cell structure, remold the foam, and increase the foam compressive strength. The development of microcellular PIFs with ultrahigh compressive strength and high volume expansion ratio remains a challenge. Herein, thermoplastic PI with a branched structure and flexible ether bonds was synthesized through solution polymerization, and microcellular thermoplastic PIFs (TPIFs) with ultrahigh strength were fabricated via supercritical-carbon-dioxide foaming using 2,4,6-triamino pyrimidine (TAP) as a chain-extender monomer. Subsequently, a lattice model of a closed tetrakaidecahedral cell was used to clarify the relation between the foam compressive strength and polymer cell structure. Experimental results indicate that the optimal thermal imidization temperature is 230 °C and that the resulting branched structure considerably improves viscoelasticity, flame retardancy, and foaming performance. A TAP content of 0.75 g results in branched-structure TPIFs with a mean cell size of 16.8 μm. Notably, at high temperatures and pressures, the compressive strength of TPIFs with 0.75 g TAP is more than nine times of that of TPIFs without TAP. Increasing the TAP content beyond 0.75 g results in a crosslinked structure. Backward differentiation shows that TPIF compression is constant at 0.14–0.18 in the [0,0,1] lattice direction. The proposed physical foaming method is environment-friendly and can sustainably produce TPIFs with a high volume expansion ratio, an adjustable microcellular structure, and outstanding mechanical properties. [Display omitted] • Branched thermoplastic polyimide (TPI) synthesized via solution polymerization. • TPI offers superb flame resistance and recyclability for fireproofing. • Microcellular TPI foams are fabricated by supercritical CO 2 foaming. • TPI foams exhibit uniform structure and strong compressive strength. • Lattice model clarifiies the relationship between compressive strength and polymer cell structure. [ABSTRACT FROM AUTHOR]

Addressing water pollution issues is directly related to green sustainable development. In this work, a heterostructure polyurethane-based (PU) sponge was prepared by a facile "dip-adhere" strategy to achieve simultaneous and efficient removal of oils and dyes from water. This innovatively designed sponge comprises two functional layers. The hydrophobic/lipophilic octadecylamine-molybdenum disulfide coated PU sponge (ODA-MoS 2 @PU) layer exhibits excellent sorption capacity, ranging from 37.35 to 63.52 times its own weight, for eight organic solvents (DMSO, isopropanol, n-hexane, petroleum ether, n-butanol, glycol, acetone, xylene) and five oils (soybean oil, olive oil, gasoline, diesel, and lubrication). Furthermore, it exhibits robust stability in extreme environments and maintains a high separation efficiency (99 % after 50 separations). The photocatalytic/superhydrophilic polydopamine-molybdenum disulfide coated PU sponge (PDA-MoS 2 @PU) layer demonstrates great photocatalytic degradation efficiency for dyes (96.80 % for methylene blue and 97.39 % for methyl orange). Consequently, the heterostructure PU sponge holds application potential in environment remediation. [Display omitted] • A dual-functional heterostructure sponge was prepared. • Continuous oil-water separation was realized with the oil-gathering device. • The simultaneous treatment of removing oils and dyes was achieved. [ABSTRACT FROM AUTHOR]