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This work aims to systematically examine the topology effect on the self-assembly of block copolymers. Compositionally, symmetric polystyrene-block-polydimethylsiloxane block copolymers (BCPs) with different chain topologies (diblock, three-arm star-block, and four-arm star-block) and various molecular weights are synthesized. These purposely designed block copolymers are used as a model system to investigate the topology effect on order-to-disorder transition temperature (TODT) by temperature-resolved small-angle X-ray scattering experiments. An increase of the TODTis observed when the arm number of BCPs with equivalent arm length (i.e., molecular weight) is increased from one to four. Based on the random-phase approximation (RPA), Flory–Huggins interaction parameter (χ) is determined from the regression of the measured TODT. The observation by differential scanning calorimetry also demonstrates the shifting of the endothermic peak from the order-to-disorder transition of star-blocks to the higher temperature region, consistent with the scattering experiments and the RPA prediction.

Structured diblock copolymer liquids consisting exclusively of “soft” segments with glass-transition temperatures well below room temperature have not been studied extensively in the literature in terms of self-assembly properties to date. Despite their “soft nature”, these types of diblock copolymers are capable of forming well-ordered topologies at low temperatures. This ability is attributed to their low dispersity indices (Đ) and relatively high Flory–Huggins interaction parameter, χ, between the chemically different involved blocks. Herein, we report a comprehensive study of the synthesized copolymers on molecular and thermal characterization, along with the structure–property relationship of two types of polydiene-b-polysiloxane copolymers by manipulating the monomer’s ratio during synthesis. Emphasis was given to the self-assembly behavior when the molecular characteristics (volume fraction and degree of polymerization) of the involved blocks varied to assess the limits of the phase stability. Specially, poly(butadiene) (PB1,2) or poly(isoprene) (PI1,4) was utilized as the first segment, while poly(dimethylsiloxane) (PDMS) was used as the second block in all cases. The molecular characteristics’ diversity combined with the ability to design/synthesize block copolymers with well-ordered phases ranging from spheres, cylinders, lamellar, and finally network structures is quite promising for nanotechnology applications in soft electronics. Also, the inherent properties of the copolymers, such as thermal stability, hydrophobicity, and flexibility, render them potential candidates for stretchable and/or wearable applications.

The polygenic nature of autism spectrum disorder (ASD) requires the identification of converging genetic pathways during early development to elucidate its complexity and varied manifestations.

This work demonstrates a simple approach to control the orientation of the self-assembled nanostructured block copolymer thin films of polystyrene-block-polydimethylsiloxane (PS-b-PDMS) by functionalization of the oxide layer (SiO2) on the Si substrate followed by thermal annealing under low-pressure environmental conditions. The substrate can be functionalized through two-step grafting of hydroxy-terminated polystyrene brush (PS–OH brush) followed by hydroxy-terminated polydimethylsiloxane brush (PDMS–OH brush) onto the wafer substrate. By controlling the grafting ratio of PS–OH and PDMS–OH brushes, the affinities of the PS and PDMS blocks with the substrates can be fine-tuned to provide a neutral substrate in order to form perpendicular cylinders from the bottom after thermal annealing. Owing to the vacuum-driven orientation [i.e., thermal annealing under low-pressure environment conditions (∼10–4Pa)], the orientation of the cylinders can be controlled at the air/polymer interface. Interestingly, by combining the vacuum-driven approach with substrate functionalization, perpendicular cylinders from the air/polymer interface and substrate/polymer interface can be generated, respectively. Consequently, well-aligned perpendicular cylinders with long-range ordering can be fabricated by the self-alignment process.

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-block-polydimethylsiloxane (PS-b-PDMS), is chosen to demonstrate vacuum-driven orientation for solving the notorious low-surface-energy problem of silicon-based BCP nanopatterning. By taking advantage of the pressure dependence of the surface tension of polymeric materials, a neutral air surface for the PS-b-PDMS thin film can be formed under a high vacuum degree (∼10–4Pa), allowing the formation of the film-spanning perpendicular cylinders and lamellae upon thermal annealing. In contrast to perpendicular lamellae, a long-range lateral order for forming perpendicular cylinders can be efficiently achieved through the self-alignment mechanism for induced ordering from the top and bottom of the free-standing thin film.

Three new high-entropy alloys of the Ni–Al–Cr–Mo–W system were produced by vacuum arc melting and assessed concerning their microstructure and sliding wear resistance. The NiAl content was kept constant at 60 at.%, and three alloys, namely NiAl–25Cr–7.5Mo–7.5W, NiAl–20Cr–10Mo–10W and NiAl–15Cr–12.5Mo–12.5W, were investigated by changing the relative ratios between Cr–Mo–W. All microstructures were found to consist of primary phases, eutectic microconstituent, a small amount of Al–Cr-based intermetallic phases and precipitated phases after spinodal decomposition. Adiabatic conditions, originated from the presence of tungsten with the highest melting point and its leading role in the initiation of solidification, were proved to affect the extent and morphology of features like the eutectic microconstituent. In particular, higher concentrations of W–Mo caused more powerful adiabatic conditions and, thus, thicker eutectic growing radially in a partitioning mode. The sliding wear response of the produced system seems to follow the classical sliding wear laws of Archard. This behaviour is further supported by multiple factors, such as the nature of the oxide phases being formed upon sliding and the integrity and rigidity of the interface between the primary and secondary phases.

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’ systems1. 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 both2,3. ‘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.

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 perpendicularly oriented cylinders followed by lateral ordering of the cylinders. This discovery provides an insight into the mechanisms of confined self-assembly of BCP for the engineering of nanostructured thin films with controlled orientation and long-range order.

In this work, we present a novel small molecule based on dithienylthienothiadiazole units (named SM1) acting as an efficient component in ternary blend organic solar cells to modify the hole extraction at the interface. Our findings show that the SM1 suppresses the surface recombination and enhances the open-circuit voltage (Voc). By introducing SM1 in a host system composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), we obtained Vocvalues of up to 0.75 V and fill factors larger than 70% for the ternary blends. As a consequence, the power conversion efficiency is improved by about 30% compared to P3HT:PCBM binary devices. Interestingly, external quantum efficiency and absorption spectra in the near-infrared region do not show any contribution of SM1 in dried films. Instead, the addition of the small molecule improves the Vocby reducing the surface recombination losses. To shed light on the recombination processes, we carried out Fourier-transform photocurrent spectroscopy and impedance spectroscopy measurements. This work shows that the ternary concept can also have functionalities other than photosensitization and can even act as a morphology-directing agent or an interface modifier.

A combined experimental and self-consistent-field theoretical (SCFT) investigation of the phase behavior of poly(stryrene-b-dimethylsiloxane-b-styrene) (PS-b-PDMS-b-PS, or SDS32) thin films during solvent vapor annealing is presented. The morphology of the triblock copolymer is described as a function of the as-cast film thickness and the ratio of two different solvent vapors, toluene and heptane. SDS32 formed terraced bilayer morphologies even when the film thickness was much lower than the commensurate thickness. The morphology transitioned between bilayer cylinders, bilayer perforated lamellae, and bilayer lamellae, including mixed structures such as a perforated lamella on top of a layer of in-plane cylinders, as the heptane fraction during solvent annealing increased. SCFT modeling showed the same morphological trends as a function of the block volume fraction. In comparison with diblock PS-b-PDMS with the same molecular weight, the SDS32 offers a simple route to produce a diversity of well-ordered bilayer structures with smaller feature sizes, including the formation of bilayer perforated lamellae over a large process window.

A conjugated donor–acceptor polymer, poly[4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-2,7-diyl-alt-5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl] (PIDT-TPD), is blended with the fullerene derivative [6,6]phenyl-C61-butyric acid methyl ester (PC61BM) for the fabrication of thin and solution-processed organic photodetectors (OPDs). Systematic screening of the concentration ratio of the blend and the molecular weight of the polymer is performed to optimize the active layer morphology and the OPD performance. The device comprising a medium molecular weight polymer (27.0 kg/mol) in a PIDT-TPD:PC61BM 1:1 ratio exhibits an external quantum efficiency of 52% at 610 nm, a dark current density of 1 nA/cm2, a detectivity of 1.44 × 1013Jones, and a maximum 3 dB cutoff frequency of 100 kHz at −5 V bias. These results are remarkable among the state-of-the-art red photodetectors based on conjugated polymers. As such, this work presents a functional organic active material for high-speed OPDs with a linear photoresponse at different light intensities.

We report on the photovoltaic parameters, photophysical properties, optoelectronic properties, self-assembly, and morphology variations in a series of high-performance donor–acceptor (D–A) π-conjugated polymers based on indacenodithiophene and quinoxaline moieties as a function of the number-average molecular weight (Mn̅), the nature of aryl substituents, and the enlargement of the polymer backbone. One of the most important outcome is that from the three optimization approaches followed to tune the chemical structure toward enhanced photovoltaic performance in bulk heterojunction solar cell devices with the fullerene derivative [6,6]-phenyl-C71-butyric acid methyl ester as the electron acceptor, the choice of the aryl substituent is the most efficient rational design strategy. Incorporation of thienyl rings as substituents versus phenyl rings accelerates the electron–hole extraction process to the respective electrode, despite the slightly lower recombination lifetime and, thus, improves the electrical performance of the device. Single-junction solar cells based on ThIDT-TQxT feature a maximum power-conversion efficiency of 7.26%. This study provides significant insights toward understanding of the structure–properties–performance relationship for D–A π-conjugated polymers in solid state, which provide helpful inputs for the design of next-generation polymeric semiconductors for organic solar cells with enhanced performance.