Chiral block copolymers (BCPs*) comprising chiral entities were designed to fabricate helical architectures (i.e., twisted morphologies) from self-assembly. A new helical phase (H*) with P622 symmetry was discovered in the self-assembly of poly(styrene)-b-poly(l-lactide) (PS-PLLA) BCPs*. Hexagonally packed, interdigitated PLLA helical microdomains in a PS matrix were directly visualized by electron tomography. The phase diagram of the PS-PLLA BCPs* was also established. Phase transitions from the H* phase to the stable cylinder and gyroid phases were found after long-time annealing, suggesting that the H* is a long-lived metastable phase. In contrast to racemic poly(styrene)-b-poly(d,l-lactide) BCPs, chiral interaction significantly enhances the incompatibility between achiral PS and chiral PLLA blocks in the PS-PLLA BCPs* and can be estimated through the determination of the interaction parameter.

Developments of single crystal ED patterns in melt-crystallized poly(trimethylene terephthalate) (PTT) have been successfully achieved. Five different zonal electron diffraction patterns containing a total of 14 independent reflections were obtained. The PTT structure under strain-free conditions was identified as a triclinic structure with a ) 4.5 Å, b ) 6.3 Å, c ) 18.2 Å, R ) 97.5°, ) 91.4°, and γ ) 111.7°with a calculated density of 1.44 g/cm 3 . On the basis of the corresponding reflections in ED patterns, each significant diffraction peak in wide-angle X-ray diffraction powder pattern was identified and indexed.A much more precise determination of the unit cell parameters has been thus achieved. They are a ) 4.53 Å, b ) 6.20 Å, c ) 18.70 Å, R ) 97.6°, ) 93.2°, and γ ) 110.1°. Unlike poly(butylene terephthalate), structure deformation has not been found in PTT fibers after removal of the extension. This specific feature may explain the better performance in resilience recovery for PTT as compared to PET and PBT. Banded spherulite with negative birefringence has been observed in PTT under polarized light microscopy. The formation of banded spherulites is attributed to lamellar twisting. The twisting mechanism was evidenced by the observations of wavylike morphology from reflected light microscopy and transmission electron microscopy. The geometry of crystal lamellae has been identified according to lamellar morphology and its correlated single-crystal ED patterns. The PTT lamellae grow from the basal plane consisting of a and b axes. In connection with the observed morphology, we suggest that the lamellar twisting is attributed to the tilted chain stems which are nonorthogonal to fold surface. The nonorthogonal geometry results from the growth of PTT lamellae with triclinic structure where internal stress is gradually accumulated so as to drive the crystal twist along the radial direction of spherulite.

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.

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The engineering of structures across different length scales is central to the design of novel materials with controlled macroscopic properties. Herein, we introduce a unique class of self-assembling materials, which are built upon shape-and volume-persistent molecular nanoparticles and other structural motifs, such as polymers, and can be viewed as a size-amplified version of the corresponding small-molecule counterparts. Among them, "giant surfactants" with precise molecular structures have been synthesized by "clicking" compact and polar molecular nanoparticles to flexible polymer tails of various composition and architecture at specific sites. Capturing the structural features of small-molecule surfactants but possessing much larger sizes, giant surfactants bridge the gap between small-molecule surfactants and block copolymers and demonstrate a duality of both materials in terms of their self-assembly behaviors. The controlled structural variations of these giant surfactants through precision synthesis further reveal that their selfassemblies are remarkably sensitive to primary chemical structures, leading to highly diverse, thermodynamically stable nanostructures with feature sizes around 10 nm or smaller in the bulk, thin-film, and solution states, as dictated by the collective physical interactions and geometric constraints. The results suggest that this class of materials provides a versatile platform for engineering nanostructures with sub-10-nm feature sizes. These findings are not only scientifically intriguing in understanding the chemical and physical principles of the self-assembly, but also technologically relevant, such as in nanopatterning technology and microelectronics. giant molecules | shape amphiphiles | hybrid materials | microphase separation | colloidal particles P hysical properties of materials are dictated by the hierarchical arrangements of atoms, molecules, and supramolecular assemblies across different length scales. The construction and engineering of structures at each length scale, especially at the 2-to 100-nm scale (1), are critically important in achieving desired macroscopic properties. As the traditional top-down lithography techniques face serious challenges in fabricating 2D and 3D nanostructured materials with sub-20-nm feature sizes (2), the bottom-up approach based on self-organization or directed assembly of functional molecules provides a promising alternative. The past decades have witnessed the development of diverse self-assembly building blocks ranging from small-molecule surfactants (3), block copolymers (4), and dendrimers (5) to DNAs (6, 7), peptides (8), and proteins (9). Notably, these motifs have enabled the programmed self-assembly of nanomaterials as demonstrated in DNA-coated nanoparticles (10-13). These studies have greatly improved our understanding of the thermodynamics and kinetics of self-assembly processes and opened enormous possibilities in modern nanotechnology.Noncovalent interactions, such as hydrogen bonding, amphiphilic effect, π-π interacti...

Nanoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-b-poly(l-lactide) (PS-PLLA), followed by the hydrolysis of PLLA blocks. A well-defined nanohybrid material with SiO2 gyroid nanostructure in a PS matrix can be obtained using the nanoporous PS as a template for sol-gel reaction. After subsequent UV degradation of the PS matrix, a highly porous inorganic gyroid network remains, yielding a single-component material with an exceptionally low refractive index (as low as 1.1).

A series of liquid crystalline polyethers has been synthesized from 1-(4-hydroxy-4‘-biphenylyl)-2-(4-hydroxyphenyl)propane and α,ω-dibromoalkanes [TPP(n)]. From the differential scanning calorimetry experiments, the TPP(n=odd)s show multiple phase transitions during cooling and heating. For each TPP(n=odd) the supercooling dependence of these transitions is found to be small. A phase diagram of the transition temperatures and the enthalpy and entropy changes of the transitions with respect to the number of methylene units (n) for TPP(n=odd)s have been obtained. Analyses have been conducted regarding the contributions of both the mesogenic groups and the methylene units to the differently ordered structures. Identification of the ordered structures in each phase has been carried out by combining wide angle X-ray powder and fiber diffraction experiments at different temperatures with polarized light and transmission electron microscopy experiments on the liquid crystal morphology and defects. It is found that for TPP(n≤13)s the highest temperature transition is from the isotropic melt to a nematic phase. However, for TPP(n≥15)s, the isotropic melt directly converts to a smectic F phase having a monoclinic unit cell (a pseudohexagonal packing tilted toward a side). The WAXD fiber patterns for this phase show that the chain orientation is parallel to the fiber direction. For TPP(n≤13)s formation of a smectic F phase with a monoclinic unit cell from the nematic phase can also be determined and the WAXD fiber pattern shows that the chain orientation is at an angle ranging between 0 and 20° with respect to the fiber direction. With an increase in the number of methylene units, this angle gradually decreases until n = 15, where this angle becomes zero. Further cooling leads to a smectic crystal G phase for all TPP(n=odd)s, and the different chain orientations with respect to the fiber direction in the WAXD fiber patterns still exist. TPP(n≤9)s remain in the smectic crystal G phase down to their glass transition temperatures, while TPP(n≥11)s form a smectic crystal H phase (a tilted herringbone, orthorhombic packing tilted toward the b-axis side, and a > b) in a low temperature range.

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