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This work aims to demonstrate a facile method for the controlled orientation of nanostructures of block copolymer (BCP) thin films. A simple diblock copolymer system, polystyrene

Cold-crystallized PDLA was studied by time-resolved VCD analysis, providing molecular level insights for crystallization via intra- and inter-chain chiral interactions.

This paper presents a facile method for fabricating a thin-film sample with a high asymmetry value of induced circularly polarized luminescence (iCPL) (|g

Inspired by Mantis shrimp, this work aims to suggest a bottom-up approach for the fabrication of nanonetwork hydroxyapatite (HAp) thin film using self-assembled polystyrene

Significant enhancement of segment-scale chirality, as measured by vibrational circular dichroism (VCD), is observed in the helical phase (H*) of polylactide-based chiral block copolymers (BCPs*) due to the mesoscale chirality of the microphase-separated domains. Here, we report a weaker, yet meaningful, enhancement on the VCD signal of a double gyroid phase (DG) as compared to a double diamond phase (DD) and disordered phase from the same diblock BCPs*. Residual VCD enhancement indicates a weak degree of chiral symmetry breaking, implying the formation of a chiral double gyroid (DG*) instead of the canonical achiral form. Calculations on the basis of orientational self-consistent field theory, comparing coupling between the segmental-scale preference of an intradomain twist and morphological chirality, show that a transition between DG and DG* takes place above the critical chiral strength, driving a weak volume asymmetry between the two enantiomeric single networks of DG*. The formation of nanostructures with controllable mesoscale chiral asymmetry indicates a pathway for the amplification of optical activity driven by self-assembly.

Here, we aim to comprehend the mechanism of the order–order transition (OOT) from nonequilibrium, metastable phase to equilibrium phase. Polystyrene-block-polydimethylsiloxane (PS-PDMS) block copol...

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 (g

Spiral hierarchical superstructures were found in the self-assembly of chiral block copolymers (BCPs*) composed of a chiral poly(l-lactide) (PLLA) and an achiral polystyrene (PS) as major and minor blocks, respectively. The PLLA helical chain with semiflexible rod-like character as compared to the random coil of PS results in self-assembly with a conformational asymmetry effect overwhelming the compositional one. Consequently, instead of the forming PS cylinder microdomains in the PLLA matrix, a smectic liquid-crystal-like bilayer sandwiched with PLLA and PS microdomains will be formed. Owing to twisting and bending due to the chiral cholesteric liquid-crystal-like force field combined with steric hindrance at the chiral interface, the forming bilayers (twisted ribbon) will develop into either a concentric lamellar texture from scrolling or roll-cake textures from spiraling. This study might bring a concept for the formation of spiral hierarchical superstructures from self-assembled bilayers for device application.

Herein, we aim to examine the topological effects of block copolymer architecture on the self-assembly of lamellae-forming star-block copolymers (BCPs) composed of polystyrene (PS) and poly(dimethy...

Herein, we aim to suggest a facile method for fabrication of Ni-based nanonetworks via templated electroless plating using mesoporous polymers as templates. With the control of spinodal decomposition for the polymer/crystalline solvent mixture, it is feasible to fabricate mesoporous polystyrene with controlled porosity and pore size as well as its distribution that could serve as a template for templated electroless plating. By taking advantage of the development of reduced Ni from the electroless plating, nanoporous Ni spheres with controlled micrometer-sized particle could be directly acquired, providing the feasibility as heterogeneous catalysts in aimed reactions. With the high specific surface area, the fabricated nanonetwork Ni gave rise to superior performance for catalytic hydrogenation of unsaturated organics and polymers. With the magnetic properties of Ni, catalyst recyclability could be simply achieved by magnetic field. This approach is simple and cost-effective to create nanoporous Ni spheres with high catalytic efficiency and well selectivity for hydrogenation performance.

The interplay between polymer-polymer and polymer-solvent interactions as well as interactions that impose secondary structures determines the conformation of polymer chains in dilute solution. Polypeptoids-poly(

Herein, we aim to create new phases with chiral sense from the self-assembly of block copolymers (BCPs). The main idea is to create a BCP with a chiral block, yielding BCPs with a helical polymer chain for self-assembly in the bulk; this BCP system is denoted as a chiral BCP (BCP*). With the introduction of chirality effects in BCP self-assembly, a helical phase (H*) with hexagonally packed twisted cylinders can be obtained. By taking advantage of the homochiral evolution from a monomer to a polymer chain and further extending to a hierarchical superstructure, controlled chirality of H* can be achieved; this phase is, therefore, referred to as one of the mesochiral phases from the self-assembly of BCPs*. A methodology to scrutinize chirality transfers at different length scales for BCP* self-assembly was, therefore, developed by using electronic circular dichroism, vibrational circular dichroism, and electron microscopy tomography for the examination of monomer chirality (optical activity of the molecule), polymer chain chirality (intrachain chiral interactions), and hierarchical chirality (twisting of multichain mesodomain attributable to interchain chiral interactions), respectively. The chirality effects and the corresponding homochiral evolution during BCP self-assembly have been proven to be experimentally generic and supported by the tilted chiral lipid bilayer model and orientational self-consistent field theory. Most interestingly, the formed helical cylinder can serve as the stepping stone for the formation of a network phase, namely, a gyroid, via twisting to yield a wide region for the formed network phase. With the easy development of the gyroid phase, a platform technology, referred as templated syntheses, for the fabrication of nanonetwork-structured materials was, therefore, developed. Consequently, various gyroid-structured materials could be fabricated via templated atomic layer deposition, electroplating, electroless plating, sol–gel reaction, and polymerization to yield well-ordered nanonetwork semiconductive, metallic, ceramic, and polymeric materials after template removal. Note that the hidden chirality of the gyroid can be defined by using the dihedral (torsion) angle concept from the simplified building unit with a tripod texture. With the controlled chirality of the helical cylinder and chiral network, it is appealing and promising to fabricate chiral materials by combining the mesochiral self-assembly and platform technology of templated syntheses, yielding well-ordered nanohybrids and nanoporous materials with helical sense. By taking advantage of the deliberate structuring, the fabrication of chiral metamaterials with appealing applications in negative refractive index materials, devices with giant optical activity, and beam splitters can be expected.

Herein, we aim to develop a facile method for the fabrication of mechanical metamaterials from templated polymerization of thermosets including phenolic and epoxy resins using self-assembled block copolymer, polystyrene-polydimethylsiloxane with tripod network (gyroid), and tetrapod network (diamond) structures, as templates. Nanoindentation studies on the nanonetwork thermosets fabricated reveal enhanced energy dissipation from intrinsic brittle thermosets due to the deliberate structuring; the calculated energy dissipation for gyroid phenolic resins is 0.23 nJ whereas the one with diamond structure gives a value of 0.33 nJ. Consistently, the gyroid-structured epoxy gives a high energy dissipation value of 0.57 nJ, and the one with diamond structure could reach 0.78 nJ. These enhanced properties are attributed to the isotropic periodicity of the nanonetwork texture with plastic deformation, and the higher number of struts in the tetrapod diamond network in contrast to tripod gyroid, as confirmed by the finite element analysis.

The development of well ordered nanonetwork materials from basic building blocks to the bulk phase is examined by simplifying the scattering from the form factor of a sphere convoluted with the nodes of the structure factor, providing a simple methodology for studying the formation of well ordered nanonetwork materials., The development of well ordered nanonetwork materials (in particular gyroid-structured materials) has been investigated using a block-copolymer template for templated electroless plating as an example system for the examination of network formation using X-ray scattering. By taking advantage of the nucleation and growth mechanism of templated electroless plating, gyroid-structured Au was successfully fabricated through the development of Au nanoparticles, then tripods and branched tripods, and finally an ordered network. Each stage in the development of the network phase could then be examined by combining real-space transmission electron microscopy observations with reciprocal-space small-angle X-ray scattering results. The fingerprint scattering profile of the building block for the network (i.e. the tripod of the gyroid) could be well fitted with the form factor of an effective sphere, and the diffraction results from the ordered network could thus be reasonably addressed. As a result, the examination of well ordered network materials can be simplified as the scattering from the form factor of a sphere convoluted with the nodes of its structure factor, providing a facile method of identifying the network phases from X-ray scattering data.

Herein, we aim to examine the order-order transition (OOT) of self-assembled block copolymer (BCP) under spatial confinement using double gyroid (DG) structured polystyrene-block-polydimethylsiloxane (PS-PDMS) thin film as an exemplary system for three-dimensional (3D) visualization of phase transitions. An interesting OOT from DG to hexagonally perforated lamellae (HPL) can be found after thermal annealing, and the morphological evolution and corresponding mechanism for the OOT was systematically investigated by 3D transmission electron microscopy (3D TEM). Our results revealed that the phase transition of DG nanostructure in thin film was different from that in bulk, which is attributed into the surficial/interfacial effects and the effect of confinement on BCP self-assembly. This work provides a feasible method to prepare DG-nanostructured thin film and presents a model system for the examination of morphological evolution from metastable to phase with higher thermodynamic stability in the thin-film state through the OOT.

We explore the generality of the influence of segment chirality on the self-assembled structure of achiral–chiral diblock copolymers. Poly(cyclohexylglycolide) (PCG)-based chiral block copolymers (BCPs*), poly(benzyl methacrylate)-b-poly(d-cyclohexylglycolide) (PBnMA-PDCG) and PBnMA-b-poly(l-cyclohexyl glycolide) (PBnMA-PLCG), were synthesized for purposes of systematic comparison with polylactide (PLA)-based BCPs*, previously shown to exhibit chirality transfer from monomeric unit to the multichain domain morphology. Opposite-handed PCG helical chains in the enantiomeric BCPs* were identified by the vibrational circular dichroism (VCD) studies revealing transfer from chiral monomers to chiral intrachain conformation. We report further VCD evidence of chiral interchain interactions, consistent with some amounts of handed skew configurations of PCG segments in a melt state packing. Finally, we show by electron tomography [3D transmission electron microscope tomography (3D TEM)] that chirality at the monomeric and intrachain level ultimately manifests in the symmetry of microphase-separated, multichain morphologies: a helical phase (H*) of hexagonally, ordered, helically shaped tubular domains whose handedness agrees with the respective monomeric chirality. Critically, unlike previous PLA-based BCP*s, the lack of a competing crystalline state of the chiral PCGs allowed determination that H* is an equilibrium phase of chiral PBnMA-PCG. We compared different measures of chirality at the monomer scale for PLA and PCG, and argued, on the basis of comparison with mean-field theory results for chiral diblock copolymer melts, that the enhanced thermodynamic stability of the mesochiral H* morphology may be attributed to the relatively stronger chiral intersegment forces, ultimately tracing from the effects of a bulkier chiral side group on its main chain.

A series of cubic network phases was obtained from the self-assembly of a single-composition lamellae (L)-forming block copolymer (BCP) polystyrene-block-polydimethylsiloxane (PS-b-PDMS) through solution casting using a PS-selective solvent. An unusual network phase in diblock copolymers, double-primitive phase (DP) with space group of [Formula: see text] , can be observed. With the reduction of solvent evaporation rate for solution casting, a double-diamond phase (DD) with space group of [Formula: see text] can be formed. By taking advantage of thermal annealing, order–order transitions from the DP and DD phases to a double-gyroid phase (DG) with space group of [Formula: see text] can be identified. The order–order transitions from DP (hexapod network) to DD (tetrapod network), and finally to DG (trigonal planar network) are attributed to the reduction of the degree of packing frustration within the junction (node), different from the predicted Bonnet transformation from DD to DG, and finally to DP based on enthalpic consideration only. This discovery suggests a new methodology to acquire various network phases from a simple diblock system by kinetically controlling self-assembling process.

The synthesis of two (2) novel triblock terpolymers of the ABC type and one (1) of the BAC type, where A, B and C are chemically different segments, such as polystyrene (PS), poly(butadiene) (PB1,4) and poly(dimethylsiloxane) (PDMS), is reported, moreover, their corresponding molecular and bulk characterizations were performed. Very low dimensions are evident from the characterization in bulk from transmission electron microscopy studies, verified by small-angle X-ray data, since sub-16 nm domains are evident in all three cases. The self-assembly results justify the assumptions that the high Flory–Huggins parameter, χ, even in low molecular weights, leads to significantly well-ordered structures, despite the complexity of the systems studied. Furthermore, it is the first time that a structure/properties relationship was studied for such systems in bulk, potentially leading to prominent applications in nanotechnology and nanopatterning, for as low as sub-10 nm thin-film manipulations.

By taking advantage of chirality transfer, nanonetwork with controlled chirality can be obtained from self-assembly., Nanonetwork-structured materials can be found in nature and synthetic materials. A double gyroid (DG) with a pair of chiral networks but opposite chirality can be formed from the self-assembly of diblock copolymers. For triblock terpolymers, an alternating gyroid (GA) with two chiral networks from distinct end blocks can be formed; however, the network chirality could be positive or negative arbitrarily, giving an achiral phase. Here, by taking advantage of chirality transfer at different length scales, GA with controlled chirality can be achieved through the self-assembly of a chiral triblock terpolymer. With the homochiral evolution from monomer to multichain domain morphology through self-assembly, the triblock terpolymer composed of a chiral end block with a single-handed helical polymer chain gives the chiral network from the chiral end block having a particular handed network. Our real-space analyses reveal the preferred chiral sense of the network in the GA, leading to a chiral phase.

Well-ordered perpendicular cylinders of star-block copolymers (BCPs) composed of polystyrene and poly(dimethylsiloxane) blocks with high aspect ratio can be achieved by using a combination of architecture effect (entropy effect) and surface air plasma treatment (enthalpy effect). An interesting morphological evolution from disordered texture to hexagonally packed cylinders with perpendicular orientation has been observed, in which perpendicular cylinders are initiated at the top surface and bottom substrate of the thin film, followed by a self-alignment process, resulting in span-thru cylinders through the thin film. The self-alignment process is systematically examined by a combination of real space imaging using transmission electron microscopy, reciprocal space imaging using grazing incidence small-angle X-ray scattering, and three-dimensional tomography. The experimental results reveal a unique mechanism for the formation of highly ordered BCP thin films via surface-induced nucleation of perpendicular...

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.

Here we aim to develop a facile emulsion-based method to prepare tripod gold nanoparticles (AuNPs) with high suspension stability in an aqueous environment. A gyroid-structured polymer template formed by the hydrolysis of a degradable block copolymer, polystyrene (PS)-b-poly(l-lactide), is used for the fabrication of AuNPs. Also, a successful emulsification of dichloromethane (DCM) in the aqueous phase is developed by using thiolated polyethylene glycol (PEG-SH) as the stabilizer. Subsequently, the nanohybrids of PS/Au can be fabricated by templated electroless plating, and then selectively dissolving in the DCM dispersive phase. Most interestingly, a dedicated process for the simultaneous release of the tripod AuNPs from the dissolution of PS associated with PEG-SH at the interface of the emulsion is achieved, giving PEG-SH-functionalized tripod AuNPs dispersed in the aqueous phase, which significantly improves the suspension stabilization of tripod AuNPs. The in situ temperature-programmed electrospray-differential mobility analysis provides a quantitative, statistical analysis of mobility diameter, dynamic shape factor, polydispersity, and colloidal stability.

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 {\it 2D interfaces} between chemical domains; and the {\it 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 {\it network chirality} as well as {\it domain thickness}, and analyze their spatial and statistical distributions in both ideal (theoretical) and non-ideal (experimental) double gyroid assemblies., 13 pages, 7 figures, 3 pages supporting pdf

A nanoporous Ni/NiO/C nanocomposite with a gyroid nanostructure was fabricated by using a nanoporous polymer with gyroid nanochannels as a template. The polymer template was obtained from the self-assembly of a degradable block copolymer, polystyrene-b-poly(L-lactide) (PS-PLLA), followed by the hydrolysis of PLLA blocks. Templated electroless plating followed by calcination was performed to create a precisely controlled Ni/NiO gyroid nanostructure. After carbon coating, a well-interconnected nanoporous gyroid Ni/NiO/C nanocomposite can be successfully fabricated. Benefiting from the well-interconnected nanoporous structure with ultrafine transition metal oxide and uniform carbon coating, the gyroid nanoporous Ni/NiO/C nanocomposite electrodes exhibited high specific capacities at various rates (1240 mA h g−1 at 0.2 A g−1, 902 mA h g−1 at 2 A g−1 and 424 mA h g−1 at 10 A g−1) and excellent cyclability (809 mA h g−1 at 1 A g−1 after 1000 cycles, average coulombic efficiency 99.86%). This research demonstrates a universal approach for constructing a nanostructured electrode with explicitly controlled block copolymer phase separation.

Controlling the orientation of nanostructured block copolymer (BCP) thin films is essential for next-generation lithography. However, obtaining BCP with perpendicular orientation remains a challenge because of the surface selectivity to the different blocks. This challenge is especially severe for silicon-containing BCPs which is notorious for its high surface energy difference between constituted blocks. Here, we demonstrate a new approach to achieve perpendicular orientation with high aspect ratio using a combination of architecture effect (entropy effect) and surface air plasma treatment (enthalpy effect). Specifically, perpendicular cylinders of star-block copolymers composed of polystyrene and poly(dimethylsiloxane) blocks can be formed from the bottom substrate to the top surface of the thin film.

We demonstrate a new, facile gas-phase electrostatic approach to successfully quantify equivalent surface area of graphene oxide (GO) colloid on a number basis. Mobility diameter (dp,m)-based distribution and the corresponding equivalent surface area (SA) of GO colloids (i.e., with different lateral aspect ratios) were able to be identified by electrospray-differential mobility analysis (ES-DMA) coupled to a condensation particle counter (CPC) and an aerosol surface area analyzer (ASAA). A correlation of SA ∝ dp,m2.0 was established using the ES-DMA-CPC/ASAA, which is consistent with the observation by the 2-dimensional image analysis of size-selected GOs. An ultrafast surface area measurement of GO colloid was achieved via a direct coupling of ES with a combination of ASAA and CPC (i.e., measurement time was 2 min per sample; without size classification). The measured equivalent surface area of GO was ∼202 ± 7 m2 g–1, which is comparable to Brunauer–Emmett–Teller (BET) surface area, ∼240 ± 59 m2 g–1. The...