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Abstract Despite being predicted to be a thermodynamically equilibrium structure, the absence of direct experimental evidence of hexagonally close-packed spherical phase in single-component block copolymers raises uncomfortable concerns regarding the existing fundamental phase principles. This work presents a robust approach to regulate the phase behavior of linear block copolymers by deliberately breaking molecular symmetry, and the hexagonally close-packed lattice is captured in a rigorous single-component system. A collection of discrete A1BA2 triblock copolymers is designed and prepared through an iterative growth method. The precise chemical composition and uniform chain length eliminates inherent size distribution and other molecular defects. Simply by tuning the relative chain length of two end A blocks, a rich array of ordered nanostructures, including Frank−Kasper A15 and σ phases, are fabricated without changing the overall chemistry or composition. More interestingly, hexagonally close-packed spherical phase becomes thermodynamically stable and experimentally accessible attributed to the synergistic contribution of the two end blocks. The shorter A blocks are pulled out from the core domain into the matrix to release packing frustration, while the longer ones stabilize the ordered spherical phase against composition fluctuation that tends to disrupt the lattice. This study adds a missing puzzle piece to the block copolymer phase diagram and provides a robust approach for rational structural engineering.

Current polymer network design suffers from intrinsic trade-offs, where polymer networks with high modulus often turn out to be in short of stretchability or fracture toughness. Here, we show a novel polymer network design through polymer-nanoparticle alternating hybrids that enable integrating the non-polymeric colloid deformation into polymer network design. The new class of polymer network exhibits colloidal yielding at small deformation before conformational change at higher elongation ratios, enabling simultaneous achievement of high Young's modulus of E≈10−50MPa, high yield strength of σY∼3−5MPa, large stretchability of λ∼7−10, and high fracture energy density of Γ∼30MJ/m3. These results demonstrate a successful strategy to decouple the molecular mechanics for yield from that for stretchability or toughness, leading to new polymer networks design.

This work quantitatively explores the effect of chain length heterogeneity on self-assembly behaviors of block copolymer, focusing on the narrow distribution region. A library of discrete diblock copolymers consisting of oligo dimethylsiloxane (oDMS) and oligo lactic acid (oLA) blocks were modularly prepared with one monomer difference in composition, which form highly ordered nanostructures at room temperature. The molecular weight distribution of the oLA block was then precisely modulated through a reconstruction approach, achieving an absolute control on chain length heterogeneity. By meticulously tuning the breadth and symmetry of the distribution profile, the lattice dimension of the assembled nanostructure significantly expands, while no appreciable difference on the phase stability was observed. This work provides an explicit access to block copolymers with narrow dispersity that are not possible through conventional chemical approach, revealing the critical contribution of dispersity on self-assembly and bridging the existing gaps between experiments and theories.

Theself-assembly behaviors of fluorinated polyhedral oligomeric silsesquioxane(FPOSS)-based giant surfactants, consisting of an FPOSS cage and apolystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer tail, are studied in the bulk.The tethering point of the FPOSS cage on the PS-b-PEO diblock copolymer chain can be controlled precisely either atthe end of the PS block or the junction point between the PS and PEOblocks, resulting in topological isomer pairs with almost identicalchemical compositions but different architectures. Phase separationbetween the FPOSS head and the block copolymer tail creates a spatiallyconfined environment for the PS-b-PEO component,which are uniformly end- or junction-point-immobilized on the FPOSSlayer, providing a unique model system to study phase behaviors andchain conformation of tethered diblock copolymer in the condensedstate. The polymer tails are highly stretched because the cross-sectionalarea of FPOSS head is smaller than that of the unperturbed block copolymertail, which facilitates further phase separation between the low molecularweight PS and PEO blocks and leads to the formation of hierarchicallamellar structures among three mutually immiscible components. [ABSTRACT FROM AUTHOR]

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 shapeand 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. [ABSTRACT FROM AUTHOR]