Self-Assembled, Iridescent, Crustacean-Mimetic Nanocomposites with Tailored Periodicity and Layered Cuticular Structure

Abstract

Natural high-performance materials inspire the pursuit of ordered hard/soft nanocomposite structures at high fractions of reinforcements and with balanced molecular interactions. Herein, we develop a facile, waterborne self-assembly pathway to mimic the multiscale cuticle structure of the crustacean armor by combining hard reinforcing cellulose nanocrystals (CNCs) with soft poly(vinyl alcohol) (PVA). We show iridescent CNC nanocomposites with cholesteric liquid-crystal structure, in which different helical pitches and photonic band gaps can be realized by varying the CNC/PVA ratio. We further show that multilayered crustacean-mimetic materials with tailored periodicity and layered cuticular structure can be obtained by sequential preparation pathways. The transition from a cholesteric to a disordered structure occurs for a critical polymer concentration. Correspondingly, we find a transition from stiff and strong mechanical behavior to materials with increasing ductility. Crack propagation studies using scanning electron microscopy visualize the different crack growth and toughening mechanisms inside cholesteric nanocomposites as a function of the interstitial polymer content for the first time. Different extents of crack deflection, layered delamination, ligament bridging, and constrained microcracking can be observed. Drawing of highly plasticized films sheds light on the mechanistic details of the transition from a cholesteric/chiral nematic to a nematic structure. The study demonstrates how self-assembly of biobased CNCs in combination with suitable polymers can be used to replicate a hierarchical biological structure and how future design of these ordered multifunctional nanocomposites can be optimized by understanding mechanistic details of deformation and fracture.

Dielectric Characterization of Confined Water in Chiral Cellulose Nanocrystal Films

“…For example, we found the disordered films to possess a gradient in pitch from the top of the film to the bottom, which depends on the length of time spent by each CNC layer with liquid water. These results also suggest that air flow may direction be used to obtain patterned films of CNCs in all three dimensions, to realize the graded Bouligand structures seen in crustacean shells 8 or to fabricate naturally sourced metamaterials.…”

“…5,6 These attractive properties have motivated numerous endeavors toward fabricating multifunctional CNC nanocomposites using solution casting, melt processing, sol–gel, and template methods, 1,5,7 which may yield the typical low filling fraction nanocomposites (<40 mass %) or highly filled biomimetic composites with cholesteric self-assembled CNCs. 8,9 …”

Advanced Near‐Infrared Light‐Responsive Nanomaterials as Therapeutic Platforms for Cancer Therapy

“…The reaction was performed in a sealed autoclave or heating mantle at temperatures between 160 and 300°C. A class of hydrophilic ligands such as PAA, [91] trisodium citrate, [92] 3-mercaptopropionic acid (3-MPA), [92] tetramethylammonium hydroxide (TMAH), [93] PEG-phosphate, [94] and PEI [95] have all been used to cap UCNPs. Normally, surface modification is required to form hydrophilic surfaces on these UCNPs before employing them in bioanalytical applications.…”

Iridescent Chiral Nematic Mesoporous Organosilicas with Alkylene Spacers

“…[32] The CNCs arrange into a Bouligand structure, where the crystallites themselves are aligned in layers, but twist with a characteristic helical pitch, P. It is the repeating helicoidal structure that leads to diffraction of circularly polarized light from the CNC films. [30,[34][35][36][37][38][39][40][41][42][43][44][45][46][47] In 2010, we discovered that films of mesoporous silica with chiral nematic structure could be prepared using CNCs as a template. [30,[34][35][36][37][38][39][40][41][42][43][44][45][46][47] In 2010, we discovered that films of mesoporous silica with chiral nematic structure could be prepared using CNCs as a template.…”

“…[33] Many researchers are making new materials that take advantage of the unique properties of CNCs. [30,[34][35][36][37][38][39][40][41][42][43][44][45][46][47] In 2010, we discovered that films of mesoporous silica with chiral nematic structure could be prepared using CNCs as a template. [20] When Si(OR) 4 is condensed with CNCs in water, the resulting composite film contains silica and a chiral nematic assembly of CNCs.…”