Although challenging, fabrication of porous conducting polymeric materials with excellent electronic properties is crucial for many applications. We developed a fast in situ polymerization approach to pure polyaniline (PANI) hydrogels, with vanadium pentoxide hydrate nanowires as both the oxidant and sacrifice template. A network comprised of ultrathin PANI nanofibers was generated during the in situ polymerization, and the large aspect ratio of these PANI nanofibers allowed the formation of hydrogels at a low solid content of 1.03 wt %. Owing to the ultrathin fibril structure, PANI hydrogels functioning as a supercapacitor electrode display a high specific capacitance of 636 F g, a rate capability, and good cycling stability (∼83% capacitance retention after 10,000 cycles). This method was also extended to the preparation of polypyrrole and poly(3,4-ethylenedioxythiophene) hydrogels. This template polymerization method represents a rational strategy for design of conducing polymer networks, which can be readily integrated in high-performance devices or a further platform for functional composites.

The structural coloration of arthropods often arises from helicoidal structures made primarily of chitin. Although it is possible to achieve analogous helicoidal architectures by exploiting the self‐assembly of chitin nanocrystals (ChNCs), to date no evidence of structural coloration has been reported from such structures. Previous studies are identified to have been constrained by both the experimental inability to access sub‐micrometer helicoidal pitches and the intrinsically low birefringence of crystalline chitin. To expand the range of accessible pitches, here, ChNCs are isolated from two phylogenetically distinct sources of α‐chitin, namely fungi and shrimp, while to increase the birefringence, an in situ alkaline treatment is performed, increasing the intensity of the reflected color by nearly two orders of magnitude. By combining this treatment with precise control over ChNC suspension formulation, structurally colored chitin‐based films are demonstrated with reflection tunable from blue to near infrared.

A key requirement for the understanding of crystal growth is to detect how new layers form and grow at the nanoscale. Multistage crystallization pathways involving liquid-like, amorphous or metastable crystalline precursors have been predicted by theoretical work and have been observed experimentally. Nevertheless, there is no clear evidence that any of these precursors can also be relevant for the growth of crystals of organic compounds. Herein, we present a new growth mode for crystals of DL-glutamic acid monohydrate that proceeds through the attachment of preformed nanoscopic species from solution, their subsequent decrease in height at the surface and final transformation into crystalline 2D nuclei that eventually build new molecular layers by further monomer incorporation. This alternative mechanism provides a direct proof for the existence of multistage pathways in the crystallization of molecular compounds and the relevance of precursor units larger than the monomeric constituents in the actual stage of growth.

A solution-based, low-cost dip-coating method was explored to assemble cellulose nanocrystals (CNCs) into a uniaxial thin film, as confirmed by multiple microscopic tools on multiple length scales.Furthermore, this approach is readily modified for the coassembly of CNCs and a tough 1D nanoitemsingle-walled carbon nanotubes into a uniaxial array.

Epitaxial crystallization is the most prominent approach to achieving oriented thin films composed of semicrystalline polymers (SCPs). Nevertheless, current templates remain limited in fulfilling oriented SCPs with high-throughput coating processes. Herein, we report the first template for the epitaxial crystallization of SCPs based on a uniaxial assembly of shape-anisotropic nanocrystalscellulose nanocrystals (CNCs). The template was fabricated via a dip-coating method, leading to a uniaxial thin coating on both planar and nonplanar substrates. Such a thin coating functioned similarly to a laterally oriented SCP thin film in regulating the crystallization behaviors of poly(ε-caprolactone) (PCL). The orientational relationship between the CNC thin coating and the PCL overlayer was studied systematically by employing multiple characterization tools including scattering, diffraction, and microscopy. Moreover, the epitaxial match based on the crystallography-regulated hydrogen-bonding networks between the two layers was confirmed by molecular modeling, in agreement with the experimental results. Besides the orientational regulation, CNCs also promoted the crystallization kinetics of PCL effectively due to the nanoepitaxial effect provided by each CNC particle. We highlight this facile assembly approach to heterogeneous nuclei for the epitaxial crystallization of SCPs and its extendability of achieving thin coatings composed of 3D-oriented SCPs on ambient substrates.

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Semicrystalline polymers (SCPs) represent a group of cheap heterogeneous nuclei for crystallization. Nevertheless, cellulose, the most abundant biogenic SCP, is notorious for its poor processability. This limits its application as the orientational guiding agent in crystallization of functional compounds. Different from current polymer engineering approaches to uniaxial SCP thin films, we explored a novel approach to the uniaxial cellulose thin film via the oriented assembly of cellulose nanocrystals (CNCs) by means of a simple dip-coating technique. This thin film successfully guides the lateral crystallization of two drug compounds, which in turn reflects the uniformity of the uniaxial CNC alignment on the macroscopic scale. Furthermore, unlike traditional SCP thin films, the assembly route driven by different external forces can lead to CNC thin films with distinct orientational characters for fabrication of patterned drug thin films. The emerging colloidal assembly route to a uniaxial SCP substrate leads to unprecedented access to design heterogeneous nuclei for oriented crystallization of functional hybrids.

Biomineralization provides load-bearing and protective functions to living organisms by reinforcing soft tissues. Translation of biomineralization principles to materials science in a controlled and self-organized fashion is highly desirable but challenging. A major lesson from natural systems is that crystallization may be controlled by compartmentalization and templating. Here, we develop a crystallization technique based on graphene oxide-mediated compartmentalization and on templating prismatic growth of calcite nanocoatings via control of ionic diffusivity into the microcompartments, which results in a multistage, self-organized crystallization and represents an effective strategy for providing continuous nanocoatings and enhancing the tribological performance of polymeric surfaces under contact stresses. The present research offers a bottom-up approach of using very basic biomineralization principles for the protection of polymeric surfaces, which are of interest for biomedical applications and the fabrication of high-performance functional materials in a sustainable manner.