Self-Assembled Bioinspired Nanocomposites

Abstract

Metrics & MoreArticle Recommendations CONSPECTUS: Bioinspired materials engineering impacts the design of advanced functional materials across many domains of sciences from wetting behavior to optical and mechanical materials. In all cases, the advances in understanding how biology uses hierarchical design to create failure and defect-tolerant materials with emergent properties lays the groundwork for engaging into these topics. Biological mechanical materials are particularly inspiring for their unique combinations of stiffness, strength, and toughness together with lightweightness, as assembled and grown in water from a limited set of building blocks at room temperature. Wood, nacre, crustacean cuticles, and spider silk serve as some examples, where the correct arrangement of constituents and balanced molecular energy dissipation mechanisms allows overcoming the shortcomings of the individual components and leads to synergistic materials performance beyond additive behavior. They constitute a paradigm for future structural materials engineering in the formation process, the use of sustainable building blocks and energy-efficient pathways, as well as in the property profiles that will in the long term allow for new classes of high-performance and lightweight structural materials needed to promote energy efficiency in mobile technologies. This Account summarizes our efforts of the past decade with respect to designing self-assembling bioinspired materials aiming for both mechanical high-performance structures and new types of multifunctional property profiles. The Account is set out to first give a definition of bioinspired nanocomposite materials and self-assembly therein, followed by an in-depth discussion on the understanding of mechanical performance and rational design to increase the mechanical performance. We place a particular emphasis on materials formed at high fractions of reinforcements and with tailor-made functional polymers using self-assembly to create highly ordered structures and elucidate in detail how the soft polymer phase needs to be designed in terms of thermomechanical properties and sacrificial supramolecular bonds. We focus on nanoscale reinforcements such as nanoclay and nanocellulose that lead to high contents of internal interfaces and intercalated polymer layers that experience nanoconfinement. Both aspects add fundamental challenges for macromolecular design of soft phases using precision polymer synthesis. We build upon those design criteria and further develop the concepts of adaptive bioinspired nanocomposites, whose properties are switchable from the outside using molecularly defined triggers with light. In a last section, we discuss how new types of functional properties, in particular flexible and transparent gas barrier materials or fire barrier materials, can be reached on the basis of the bioinspired nanocomposite design strategies. Additionally, we show new types of self-assembled photonic materials that can even be evolved into self-assembling lasers, hence moving the c...

Hierarchical Interface Engineering for Advanced Nanocellulosic Hybrid Aerogels with High Compressibility and Multifunctionality

“…[ 41 ] In addition, these hybrid aerogels also show great potential as building materials to minimize the thermal energy and humidity exchange between indoor and outdoor environments for improving the energy efficiency of residential and commercial buildings. [ 9d,e ]…”

“…Renewable, sustainable, biomass materials, such as nanocellulose fibers extracted from plants and bacteria, have gained significant research interest in recent years. [ 9 ] Nanocellulose fibers show extremely high aspect ratio and high crystallinity, making them possible to act as building blocks for generating high‐performance aerogels on the basis of nanoscale engineering. [ 9e ] In previous work, an assembly of 1D nanofibers with cellular structures has been demonstrated to successfully build compressible and ultralight aerogels, owing to the existence of interpenetrate network and structural continuity.…”

“…[ 9 ] Nanocellulose fibers show extremely high aspect ratio and high crystallinity, making them possible to act as building blocks for generating high‐performance aerogels on the basis of nanoscale engineering. [ 9e ] In previous work, an assembly of 1D nanofibers with cellular structures has been demonstrated to successfully build compressible and ultralight aerogels, owing to the existence of interpenetrate network and structural continuity. [ 5 ] Due to the comparatively weak intermolecular interactions between cellulose nanofibers, various strategies have been demonstrated to create integrated aerogels by using chemical crosslinking, [ 10 ] layer‐by‐layer electrostatic coating, [ 11 ] and silylated grafting.…”

Electrical switching of high-performance bioinspired nanocellulose nanocomposites

“…Here, we focus on nanocomposites containing CNF/polymer = 50/50 w/w, as this composition is known to reveal fundamental details on molecular engineering of bioinspired nanocomposites, and has presented a good balance between stiffness, strength, and toughness 23 . In general, higher contents of CNF reinforcements in such bioinspired nanocomposites or CNF/polymer nanopapers lead to substantial stiffening and strengthening, and a less ductile behavior as a function of the content 23 , 25 , 26 . In terms of film preparation, simple evaporation of 50/50 w/w CNF/polymer dispersions delivers homogeneous films with macroscale dimensions (typically with a diameter of 5 cm and thickness of 15 µm).…”

“…For instance, bioinspired high-performance nanocomposite materials, inspired by biological load-bearing structures, are a particular material class that would strongly benefit from encoding mechanical adaptivity. These bioinspired nanocomposites aim for highly ordered hard/soft structures at high fractions of reinforcements (typically above 50 wt%) and with precisely engineered energy-dissipation mechanisms 19 – 23 . However, installing a programmable trigger and realizing an adaptation to external signals in such bioinspired nanocomposites is highly challenging as the adaptivity has to ultimately be provided through the soft component.…”