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• A biomimetic brush-like polymer with a catechol structure (ADD) was designed and developed. • The Ca 3 (PO 4) 2 was deposited on soy flour and mixed with ADD to develop a biomineralized adhesive. • The dry and wet shear strength of resultant plywood increased by 118.8% and 750%, respectively. • The adhesive has outstanding coating performance, mildew resistance, flame retardancy. The development of a formaldehyde-free soy flour adhesive with good coating ability, mildew resistance, and flame retardancy while maintaining high bond strength, is urgent but presents a challenge. Inspired by the strong adhesive performance derived from the brush-like structure of gecko toes, a brush-like polymer with a catechol group was synthesized to improve the adhesive behavior of soy flour adhesives. Prompted by the high strength derived from the biomineralized structure of oysters, Ca 3 (PO 4) 2 was sedimented on soy protein and combined with the brush-like polymer to construct a biomineralized structure, which endowed the resultant adhesive with mildew resistance and flame retardancy while maintaining high bond strength. The dry and wet shear strengths of the bonded plywood by the resultant adhesive increased by 118.8 % and 750 % relative to those of the unmodified adhesive. Moreover, the resultant adhesive possessed outstanding coating performance, superior mildew resistance (no mildew for 7 d), and high toughness (4.05 J of the work of adhesion). The limiting oxygen index of the resultant adhesive was increased from 26.4 % to 30.1 %. Thus, developing a system combined with a bioinspired biomineralized strategy and a brush-like polymer can potentially offer a template for the fabrication of hydrogels, functionalized surfaces, and composite materials. [ABSTRACT FROM AUTHOR]

The development of a water-retaining soybean flour-based adhesive with high water resistance, interfacial adhesion and mildew resistance is significant in replacing petroleum-based aldehyde-based resin. Drawing inspiration from lobster shells, soybean flour (SF), self-synthesized epoxy hyperbranched hydroxyethyl cellulose (EH) and calcium phosphate (CaP) oligomers were employed to prepare organic-inorganic hybrid composite adhesives based on hyperbranched structure. The EH component, abundant in active groups, enhanced the interfacial adhesion of the adhesives and served as an organic carrier for the mineralization of CaP oligomers. Prior to adhesive solidification, CaP oligomers mineralized to form an inorganic film akin to milk skin, which prevented water evaporation, resulting in a water retention time of 100 min for the adhesive. During adhesive curing, CaP oligomers with fluid-like behavior polymerized and mineralized, ultimately forming a continuous inorganic network of CaP crystals. This network, combined with the organic substrates (SF and EH), constituted an organic-inorganic hybrid structure, which bolstered the water and mildew resistance (20 days) of the adhesives. The prepressing intensity and wet shear strength of the resultant plywood increased by 168% and 396% to 0.67 MPa and 1.39 MPa, respectively, compared to those of the unmodified adhesive. The strength reached the leading level of the reported soybean flour adhesives. The biomimetic strategy employed here can be extended to high-performance gels and membrane materials, offering a novel modification approach for bio-composites. • Organic-inorganic hybrid composite adhesive based on hyperbranched structure was constructed. • Hyperbranched polymers enhanced interfacial adhesion and system compatibility. • CaP oligomers mineralized to form an inorganic film like milk skin to prevented water evaporation. • The adhesive has water retention, water resistance bonding performance and mildew resistance. • The strategy has significant reference for the research of gels, films and composites. [ABSTRACT FROM AUTHOR]

In this study, a strong and multifunctional soy protein adhesive was designed and developed. It was then combined with wood units to prepare a clean and electromagnetic shielding wood-based panel via simple hot press. Specifically, bio-based raw material was prepared by grafting pyrrole (PY) and dopamine hydrochloride (DOPA) in sequence on to soy protein isolate (SPI), and then combined with AgNO 3 and a self-synthesized bio cross-linker epoxidized quercetin (EQC), to develop a strong and conductive soy protein-based adhesive with mildew-proof and flame-retardant properties. A covalent cross-linked structure and noncovalent bond (hydrogen bonds and ionic bonds) were formed among SPI, EQC, DOPA, and Ag+. As well, a hybrid structure was formed via in situ polymerization of Ag NPs, resulting in an adhesive with improved water resistance. Thus, the dry and wet shear strengths of plywood bonded with resultant adhesive increased by 78% and 52.4%, respectively, relative to those of the SPI adhesive. The modified adhesive exhibited good mildew resistance (shelf life ＞ 15 d) due to the natural antibacterial properties of quercetin, and the dynamic equilibrium of Ag NPs and Ag+ in the presence of DOPA. Meanwhile, the LOI of the modified adhesive was 41.3%, which is higher than that of SPI, improving flame retardancy of the resultant plywood. Notably, the obtained adhesive exhibited conductivity owing to the presence of polypyrrole (up to 7.09 S/cm), which can be used to develop reflection-based particle board with electromagnetic shielding ability. This study provides a high-potential and feasible strategy for developing multifunctional biomass composites to replace metal and polymer materials, which is an important and practical approach to promote sustainable development of materials and reduce carbon emissions. [Display omitted] • Pyrrole and dopamine were grafted on soy protein to obtain functional raw material (MSPI). • MSPI combined with epoxidized quercetin as a bio cross-linker and Ag+, to develop a wood adhesive. • The dry and wet shear strength of resultant plywood increased by 78% and 52.4%, respectively. • The resultant adhesive has antimildew property, flame retardancy, low environmental impact. • The resultant adhesive has conductivity and can be used to make electromagnetic shielding panel. [ABSTRACT FROM AUTHOR]