The design of nanostructured materials and their corresponding morphologies has attracted intense attention because of their effectiveness in tuning electronic, optical, magnetic, and catalytic ...properties, as well as mechanical properties. Although many technologies have been explored to fabricate nanostructured materials, templated synthesis is one of the most important approaches to fabricate nanostructured materials with precisely controlled structures and morphologies from their constituent components. In this review article, we aim to highlight the use of the self-assembly of block copolymers as an emerging and powerful tool to fabricate well-defined nanomaterials with precise control over the structural dimensions and shape, as well as over the composition and corresponding spatial arrangement. After providing a brief introduction to the synthesis of regular porous materials, including silica- and carbon-based mesoporous materials, the review focuses on the fabrication of well-ordered nanoporous polymers from the selfassembly of degradable block copolymers, in particular with gyroid-forming network morphologies, as templates for the syntheses of various materials with different entities. We highlight the principles of different templated syntheses, from the fundamentals to their practical uses in the fabrication of nanohybrids and nanoporous materials; moreover, we provide an introduction to templates, precursors, solvents, and processing. Finally, some recent examples using block copolymer structure-directed nanomaterials for applications, such as solar cells, catalysis, and drug delivery, are presented. In particular, by taking advantage of the "well-ordered" structural characteristics of the gyroid texture, the properties and applications of 3D regular nanostructures, such as the photonic behavior and optical properties of gyroid-forming nanostructures, as well as of gyroid-forming metamaterials, will be emphasized. Special attention is also given to present new developments and future perspectives in this field.
Well-ordered nanomaterials are fabricated by various templated syntheses using templates from degradable block copolymers with gyroid-forming network morphologies.
Chirality transfer is essential to acquire helical hierarchical superstructures from the self‐assembly of supramolecular materials. By taking advantage of chirality transfers at different length ...scales through intra‐chain and inter‐chain chiral interactions, helical phase (H*) can be formed from the self‐assembly of chiral block copolymers (BCPs*). In this study, chiral triblock terpolymers, polystyrene‐b‐poly(ethylene oxide)‐b‐poly(L‐lactide) (PS‐PEO‐PLLA), and polystyrene‐b‐poly(4‐vinylpyridine)‐b‐poly(L‐lactide) (PS‐P4VP‐PLLA) are synthesized for self‐assembly. For PS‐PEO‐PLLA with an achiral PEO mid‐block that is compatible with PLLA (chiral end‐block), H* can be formed while the block length is below a critical value. By contrast, for the one with achiral P4VP mid‐block that is incompatible with PLLA, the formation of H* phase would be suppressed regardless of the length of the mid‐block, giving cylinder phase. Those results elucidate a new type of chirality transfer across the phase domain that is referred as cross‐domain chirality transfer, providing complementary understanding of the chirality transfer at the interface of phase‐separated domains.
The compatibility of mid‐block and chiral block is critical to the cross‐domain chirality transfer in ABC*‐type chiral triblock terpolymers. When the mid‐block is compatible with the chiral block, chirality could transfer through the mid‐domains with limited thickness. In contrast, as the mid‐block is incompatible with the chiral block, chiral interactions will be restricted, independent with the length of mid‐block.
The significance of chirality transfer is not only involved in biological systems, such as the origin of homochiral structures in life but also in man-made chemicals and materials. How the chiral ...bias transfers from molecular level (molecular chirality) to helical chain (conformational chirality) and then to helical superstructure or phase (hierarchical chirality) from self-assembly is vital for the chemical and biological processes in nature, such as communication, replication, and enzyme catalysis. In this Account, we summarize the methodologies for the examination of homochiral evolution at different length scales based on our recent studies with respect to the self-assembly of chiral polymers and chiral block copolymers (BCPs*). A helical (H*) phase to distinguish its P622 symmetry from that of normal hexagonally packed cylinder phase was discovered in the self-assembly of BCPs* due to the chirality effect on BCP self-assembly. Enantiomeric polylactide-containing BCPs*, polystyrene-b-poly(l-lactide) (PS–PLLA) and polystyrene-b-poly(d-lactide) (PS–PDLA), were synthesized for the examination of homochiral evolution. The optical activity (molecular chirality) of constituted chiral repeating unit in the chiral polylactide is detected by electronic circular dichroism (ECD) whereas the conformational chirality of helical polylactide chain can be explicitly determined by vibrational circular dichroism (VCD). The H* phases of the self-assembled polylactide-containing BCPs* can be directly visualized by 3D transmission electron microscopy (3D TEM) technique at which the handedness (hierarchical chirality) of the helical nanostructure is thus determined. The results from the ECD, VCD, and 3D TEM for the investigated chirality at different length scales suggest the homochiral evolution in the self-assembly of the BCPs*. For chiral polylactides, twisted lamellae in crystalline banded spherulite can be formed by dense packing scheme and effective interactions upon helical chains from self-assembly. The handedness of the twisted lamella can be determined by using rotation experiment of polarized light microscopy (PLM). Similar to the self-assembly of BCPs*, the examined results suggest the homochiral evolution in the crystallized chiral polylactides. The results presented in this Account demonstrate the notable progress in the spectral and morphological determination for the examination of molecular, conformational, and hierarchical chirality in self-assembled twisted superstructures of chiral polymers and helical phases of block copolymers and suggest the attainability of homochiral evolution in the self-assembly of chiral homopolymers and BCPs*. The suggested methodologies for the understanding of the mechanisms of the chirality transfer at different length scales provide the approaches to give Supporting Information for disclosing the mysteries of the homochiral evolution from molecular level.
Supramolecular soft crystals are periodic structures that are formed by the hierarchical assembly of complex constituents, and occur in a broad variety of 'soft-matter' systems
. Such soft crystals ...exhibit many of the basic features (such as three-dimensional lattices and space groups) and properties (such as band structure and wave propagation) of their 'hard-matter' atomic solid counterparts, owing to the generic symmetry-based principles that underlie both
. 'Mesoatomic' building blocks of soft-matter crystals consist of groups of molecules, whose sub-unit-cell configurations couple strongly to supra-unit-scale symmetry. As yet, high-fidelity experimental techniques for characterizing the detailed local structure of soft matter and, in particular, for quantifying the effects of multiscale reconfigurability are quite limited. Here, by applying slice-and-view microscopy to reconstruct the micrometre-scale domain morphology of a solution-cast block copolymer double gyroid over large specimen volumes, we unambiguously characterize its supra-unit and sub-unit cell morphology. Our multiscale analysis reveals a qualitative and underappreciated distinction between this double-gyroid soft crystal and hard crystals in terms of their structural relaxations in response to forces-namely a non-affine mode of sub-unit-cell symmetry breaking that is coherently maintained over large multicell dimensions. Subject to inevitable stresses during crystal growth, the relatively soft strut lengths and diameters of the double-gyroid network can easily accommodate deformation, while the angular geometry is stiff, maintaining local correlations even under strong symmetry-breaking distortions. These features contrast sharply with the rigid lengths and bendable angles of hard crystals.
This comprehensive review, summarizes recent advances in the fabrication of well-ordered block copolymer (BCP) thin films by different methods, focusing on the development of silicon-containing BCPs ...as candidates for lithographic applications. With the advantage of Si-containing blocks, these BCPs offer much smaller feature sizes due to large segregation strength and high etch contrast for the fabrication of well-defined nanopatterns with high resolution. Considering that poly(dimethylsiloxane) (PDMS)-containing BCPs are widely studied systems among Si-containing BCPs, the possibility of using PDMS-containing BCPs for lithographic applications is demonstrated through previous and ongoing key research.
BCP lithography will lead to the development of next-generation microelectronic devices by providing a simple and scalable nanopatterning method for the fabrication of microelectronic devices in which the feature sizes and geometries are controlled by tuning the chain lengths and volume fractions of the block copolymers. The control of microdomain orientation and alignment in thin film BCPs is crucial for lithographic applications. The principles and limitations of various methods to orientation are discussed, including temperature-gradient, surface modifications, solvent annealing/evaporation and other new types of annealing process.
Directed self-assembly (DSA) of BCP on topographic or chemically patterned substrates has attracted a great attention from academic and industrial research since it offers the advantage of defect free nanopatterning at large scales. The key achievements in DSA methods are elaborated in the subsequent parts of this review. New trends for lithographic applications and the applications beyond lithography using Si-containing BCPs for nanopatterning are also discussed, and finally, concluding remarks and perspectives for BCP lithography are presented.
Metallic nanoporous materials (MNMs) with well‐ordered gyroid nanostructures are fabricated using a nanoporous polymer with gyroid nanochannels as a template. Nanoporous gyroid Ni is successfully ...fabricated to give well‐ordered MNMs with high porosity and surface area. This new approach for hybridization provides a precisely controlled method to fabricate nanohybrids and MNMs for applications.
Abstract
Squamous cell carcinomas (SCCs) comprise one of the most common histologic types of human cancer. Transcriptional dysregulation of SCC cells is orchestrated by
tumor protein p63 (TP63)
, a ...master transcription factor (TF) and a well-researched SCC-specific oncogene. In the present study, both Gene Set Enrichment Analysis (GSEA) of SCC patient samples and in vitro loss-of-function assays establish fatty-acid metabolism as a key pathway downstream of TP63. Further studies identify
sterol regulatory element binding transcription factor 1 (SREBF1)
as a central mediator linking TP63 with fatty-acid metabolism, which regulates the biosynthesis of fatty-acids, sphingolipids (SL), and glycerophospholipids (GPL), as revealed by liquid chromatography tandem mass spectrometry (LC-MS/MS)-based lipidomics. Moreover, a feedback co-regulatory loop consisting of SREBF1/TP63/
Kruppel like factor 5 (KLF5)
is identified, which promotes overexpression of all three TFs in SCCs. Downstream of SREBF1, a non-canonical, SCC-specific function is elucidated: SREBF1 cooperates with TP63/KLF5 to regulate hundreds of cis-regulatory elements across the SCC epigenome, which converge on activating cancer-promoting pathways. Indeed, SREBF1 is essential for SCC viability and migration, and its overexpression is associated with poor survival in SCC patients. Taken together, these data shed light on mechanisms of transcriptional dysregulation in cancer, identify specific epigenetic regulators of lipid metabolism, and uncover SREBF1 as a potential therapeutic target and prognostic marker in SCC.
Triply-periodic networks (TPNs), like the well-known gyroid and diamond network phases, abound in soft matter assemblies, from block copolymers (BCPs), lyotropic liquid crystals and surfactants to ...functional architectures in biology. While TPNs are, in reality, volume-filling patterns of spatially-varying molecular composition, physical and structural models most often reduce their structure to lower-dimensional geometric objects: the 2D interfaces between chemical domains; and the 1D skeletons that thread through inter-connected, tubular domains. These lower-dimensional structures provide a useful basis of comparison to idealized geometries based on triply-periodic minimal, or constant-mean curvature surfaces, and shed important light on the spatially heterogeneous packing of molecular constituents that form the networks. Here, we propose a simple, efficient and flexible method to extract a 1D skeleton from 3D volume composition data of self-assembled networks. We apply this method to both self-consistent field theory predictions as well as experimental electron microtomography reconstructions of the double-gyroid phase of an ABA triblock copolymer. We further demonstrate how the analysis of 1D skeleton, 2D inter-domain surfaces, and combinations therefore, provide physical and structural insight into TPNs, across multiple length scales. Specifically, we propose and compare simple measures of network chirality as well as domain thickness, and analyze their spatial and statistical distributions in both ideal (theoretical) and non-ideal (experimental) double gyroid assemblies.
Many sophisticated chiral materials are found in living organisms, giving specific functions and required complexity. Owing to the remarkable optical properties of chiral materials, they have drawn ...significant attention for the development of synthetic materials to give optical activities for appealing applications. In contrast to a top‐down approach, the bottom‐up approach from self‐assembled systems with chiral host–achiral guest and achiral guest–chiral host for induced circular dichroism and induced circularly polarized luminescence has greatly emerged because of its cost‐effective advantage with easy fabrication for mesoscale assembly. Self‐assembled hierarchical textures with chiral sense indeed give significant amplification of the dissymmetry factors of absorption and luminescence (gabs and glum), resulting from the formation of well‐ordered superstructures and phases with the building of chromophores and luminophores. By taking advantage of the microphase separation of block copolymers via self‐assembly, a variety of well‐defined chiral nanostructures can be formed as tertiary superstructures that can be further extended to quaternary phases in bulk or thin film. In this article, a conceptual perspective is presented to utilize the self‐assembly of chiral block copolymers with chiral communications, giving quaternary phases with well‐ordered textures at the nanoscale for significant enhancement of dissymmetry factors.
The self‐assembly of chiral block copolymers with induced circular dichroism (ICD) and induced circularly polarized luminescence (iCPL) creates the formation of well‐ordered phases with textures at the nanoscale. The dissymmetry factors for the ICD and iCPL can be greately amplified by self‐assembly with the formation of a helical phase, giving appealing applications as chiroptical thin films.
Here, we report the mechanisms of chiral transfer at various length scales in the self-assembly of enantiomeric chiral block copolymers (BCPs*). We show the evolution of homochirality from molecular ...chirality into phase chirality in the self-assembly of the BCPs*. The chirality of the molecule in the BCP* is identified from circular dichroism (CD) spectra, while the handedness of the helical conformation in the BCP* is determined from a split-type Cotton effect in vibrational circular dichroism spectra. Microphase separation of the BCP* is exploited to form a helical (H*) phase, and the handedness of helical nanostructure in the BCP* is directly visualized from transmission electron microscopy tomography. As examined by CD and fluorescence experiments, significant induced CD signals and a bathochromic shift of fluorescence emission for the achiral perylene moiety as a chemical junction of the BCPs* can be found while the concentration of the BCPs* in toluene solution is higher than the critical micelle concentration, suggesting a twisting and shifting mechanism initiating from the microphase-separated interface of the BCPs* leading to formation of the H* phase from self-assembly.
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