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Through billions of years of evolution and natural selection, biological systems have developed strategies to achieve advantageous unification between structure and bulk properties. The discovery of these fascinating properties and phenomena has triggered increasing interest in identifying characteristics of biological materials, through modern characterization and modeling techniques. In an effort to produce better engineered materials, scientists and engineers have developed new methods and approaches to construct artificial advanced materials that resemble natural architecture and function. A brief review of typical naturally occurring materials is presented here, with a focus on chemical composition, nano-structure, and architecture. The critical mechanisms underlying their properties are summarized, with a particular emphasis on the role of material architecture. A review of recent progress on the nano/micro-manufacturing of bio-inspired hybrid materials is then presented in detail. In this case, the focus is on nacre and bone-inspired structural materials, petals and gecko foot-inspired adhesive films, lotus and mosquito eye inspired superhydrophobic materials, brittlestar and Morpho butterfly-inspired photonic structured coatings. Finally, some applications, current challenges and future directions with regard to manufacturing bio-inspired hybrid materials are provided.

In this study, a series of biobased polyols were prepared from olive, canola, grape seed, linseed, and castor oil using a novel, solvent/catalyst-free synthetic method. The biobased triglyceride oils were first oxidized into epoxidized vegetable oils with formic acid and hydrogen peroxide, followed by ring-opening reaction with castor oil fatty acid. The molecular structures of the polyols and the resulting polyurethane were characterized. The effects of cross-linking density and the structures of polyols on the thermal, mechanical, and shape memory properties of the polyurethanes were also investigated.

Bio-based polyols from epoxidized soybean oil and castor oil fatty acid were developed using an environmentally friendly, solvent-free/catalyst-free method. The effects of the molar ratios of the carboxyl to the epoxy groups, reaction time, and reaction temperature on the polyols' structures were systematically studied. Subsequently, polyurethane films were prepared from these green polyols. Properties of the new, soy-castor oil based polyurethane films were compared with two other polyurethane films prepared from castor oil and methoxylated soybean oil polyol, respectively. Thermal and mechanical tests showed that the polyurethane films prepared from the new polyols exhibited higher glass transition temperatures, tensile strength, Young's modulus, and thermal stability because of the higher degree of cross-linking in the new polyols. Moreover, the novel polyols, prepared using the solvent-free and catalyst-free synthetic route, were 100% bio-based and facilitate a more environmentally friendly and economical process than conventional soy-based polyols used for polyurethane production.Footnotes † Electronic supplementary information (ESI) available. See

Materials with multifunctionality or multiresponsiveness, especially polymers derived from green, renewable precursors, have recently attracted significant attention resulting from their technological impact. Nowadays, vegetable‐oil‐based waterborne polyurethanes (WPUs) are widely used in various fields, while strategies for simultaneous realization of their self‐healing, reprocessing, shape memory as well as high mechanical properties are still highly anticipated. We report development of a multifunctional castor‐oil‐based waterborne polyurethane with high strength using controlled amounts of dithiodiphenylamine. The polymer networks possessed high tensile strength up to 38 MPa as well as excellent self‐healing efficiency. Moreover, the WPU film exhibited a maximum recovery of 100 % of the original mechanical properties after reprocessing four times. The broad glass‐transition temperature of the samples endowed the films with a versatile shape‐memory effect, including a dual‐to‐quadruple shape‐memory effect.

The Hansen solubility parameters of a soy-castor oil-based polyol and a petroleum-based polyol are investigated to evaluate their miscibility for polyurethane blends. The two polyols were found to be miscible at different ratios over a temperature range from 25 to 90 °C. Blends with different ratios of these two polyols were used to prepare polyurethane foams. With increasing levels of bio-based polyol content, the density of the open cell foams increased. The thermal stability of the polyurethane foams improved, and their thermal conductivity increased, with increasing bio-content, while the foam’s compression strength decreased. This study provides a method to evaluate polyol blends for the preparation of polymeric materials that balances economic and environmental considerations.

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A solvent-free and scalable method was developed for the preparation of soybean-oil-based polyols by a thiol–ene photo-click reaction with a homemade photochemical reactor. The effect of reaction parameters, including photoinitiators, reaction time, molar ratios of thiols to carbon–carbon double bonds, and power of the mercury lamp, on the structures of the resulting polyols was investigated. The mechanism of the thiol–ene photo-click reaction was also discussed. On the basis of these novel polyols, several polyurethanes were prepared using different diisocyanates (aliphatic, cycloaliphatic, and aromatic isocyanate) and characterized. The resulting polyurethane films possess good performance, including the highest glass transition temperature of 41.3 °C, tensile strength of 15.7 MPa, and elongation at break of 471.0%.