the power conversion efficiencies (PCEs) of OSCs show rapid increase and the values have increased to over 18%. [16][17][18][19][20][21][22][23][24] However, owing to the brittle nature of small molecules, [25] the mechanical properties of polymer:NF-SMA blends are generally insufficient and can hardly meet the requirement of stretchable electronics. [26,27] The mechanical imperceptibility of OSCs requires low stiffness and high extensibility for wearable and portable applications. The human skin exhibits a ductility of about 30%, which is the benchmark for skin-wearable devices. [28] Studies have been carried out to determine the mechanical properties of nonfullerene OSCs [29][30][31] and drive the development of stretchable OSCs. [32][33][34][35] For instance, the fracture strain of the well-known PTB7-Th:(3,9-bis(2-methylene-(3-(1,1dicyanomethylene)-indanone))-5,5,11,11tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene) (ITIC) blend films decreased dramatically with the increase of ITIC, and the blend films became significantly stiffer as a result of increased elastic modulus. [26,36] Therefore, methods should be adopted to improve the stretchability and reduce the stiffness of OSCs based on polymer:NF-SMA blends.As the mechanical performance of polymer:NF-SMA blends are often poor, a representative high-efficiency Top-performance organic solar cells (OSCs) consisting of conjugated polymer donors and nonfullerene small molecule acceptors (NF-SMAs) deliver rapid increases in efficiencies. Nevertheless, many of the polymer donors exhibit high stiffness and small molecule acceptors are very brittle, which limit their applications in wearable devices. Here, a simple and effective strategy is reported to improve the stretchability and reduce the stiffness of highefficiency polymer:NF-SMA blends and simultaneously maintain the high efficiency by incorporating a low-cost commercial thermoplastic elastomer, polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS). The microstructure, mechanical properties, and photovoltaic performance of PM6:N3 with varied SEBS contents and the molecular weight dependence of SEBS on microstructure and mechanical properties are thoroughly characterized. This strategy for mechanical performance improvement exhibits excellent applicability in some other OSC blend systems, e.g., PBQx-TF:eC9-2Cl and PBDB-T:ITIC. More crucially, the elastic modulus of such complex ternary blends can be nicely predicted by a mechanical model. Therefore, incorporating thermoplastic elastomers is a widely applicable and cost-effective strategy to improve mechanical properties of nonfullerene OSCs and beyond.

The so-called lotus effect has inspired the production of highly hydrophobic wood surfaces based on a two-step process consisting of growing nanofilms on the wood substrate (Chinese fir) with silica sol followed by hydrophobization with hydrolyzed hexadecyltrimethoxysilane (HDTMS). The microstructure and chemical composition of the nanofilm coating were examined by field emission scanning electron microscopy, energy dispersive X-ray and Fourier transform infrared spectroscopy. The hydrophobicity of the treated wood was evaluated by water contact angle measurements. The results show that spherical nanoparticles were deposited uniformly on the wood surface, and the long-chain hydrophobic HDMTS was covalently linked to the surface of silica particles. The elevated hydrophobicity of wood was manifested by the water CA of about 141° on the longitudinal surface and 150° on the transverse surface.

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In this study, bark alkaline extractives from the mountain pine beetle (Dendroctonus ponderosae Hopkins) infested lodgepole pine (Pinus contorta Dougl.) was used to partially replace 30 wt % of melamine in formulating the biobased bark extractive−melamine formaldehyde (MF) resin. Results showed that the addition of the bark extractives and the type of solvent system used for resin formulation significantly affected the initial molecular weight, molecular structure, viscosity, curing behavior, postcuring thermal stability, and bonding performance of the resulting resins. The bark extractive−MF resins exhibited similar dry and wet bonding strengths to the laboratory made control MF resins formulated in the same type of solvent system. The liquid-state 13 C NMR study showed that bark extractives were reactants and incorporated into the resulting biobased MF resin structures. Bark extractives obtained from the mountain pine beetle infested lodgepole pine showed promise as a suitable partial replacement for melamine in MF resin formulations.