This study reports the lyotropic phase behavior of two poly(ethylene oxide)-b-poly(butadiene) diblock copolymers and their cross-linking in the mesophase under retention of the mesoscopic order. The lyotropic phase behavior in water was characterized by polarized light microscopy and small-angle X-ray scattering (SAXS) in the concentration range from 0 to 100 wt % and in a temperature range between 20 and 100 °C. Depending on polymer composition and concentration micellar, hexagonal, lamellar, and cubic phases are found. Their ranges as well as pronounced coexisting phase regions were determined. Several of these mesophases were cross-linked via γ-irradiation to form mesostructured hydrogels. It is shown that the cross-linked polymer gel essentially maintains the parental lyotropic order, as proven by SAXS, polarized light microscopy, and transmission electron microscopy (TEM). TEM enables imaging of the polymer gel structure and thereby the visualization of the liquid-crystalline mesophase morphologies in themselves. The lyotropic mesophases as well as the lyotropic gels were used as templates for the synthesis of mesoporous silica, which is expected to give a negative solid copy of the ordered soft matter structure. The influence of the different templates on the silica structure formation is discussed.

Viewing from the material design perspective, the sophistication of nature in generating materials with great precision provides opportunities to learn from in order to achieve the controlled generation of functional materials with well-defined architectures, ordered periodicity, and stability. Inspired by the two-dimensionality and surface chemistry of red blood cells and blood platelets, we attempted to implement the forces induced by crystallization and phase separation of amphiphilic carbohydrate-based crystalline-coil block copolymers to induce self-assembly generating two-dimensional (2D) lamellar platelet structures. With the current generation of functional 2D platelet structures via crystallization-driven self-assembly (CDSA) of block copolymers, transitioning the existing system into a biocompatible and bioactive system is mandatory in order to bring their functionality and applicability to another level. In this study, we introduce the crystallization-driven self-assembly of d-fructose-functionalized crystalline-coil block copolymers featuring poly­(ε-caprolactone) as the crystallizable core-forming block. By fine-tuning the corona length and composition, we obtained 2D platelets ranging in the scale between nanometer (183 nm, length) to micrometer size range (2–4 μm, length), with the latter featuring intrinsically highly ordered core-crystalline structure of orthorhombic single crystals as observed by the means of electron microscopy techniques and selected-area electron diffraction (SAED) experiment. We discovered the platelet structures to grow epitaxially through the addition of free polymer, forming supersized hexagonal 2D platelets (ca. 19–21 μm), in a process akin to the growth of living polymers. The seeded growth of these platelets suggests a memory effect, providing a platform for further hierarchical self-assembly and functionalization. The overall approach presents a facile strategy in fabricating the increasingly important colloidally stable bioinspired 2D structures with characteristic features and functional properties.

The assembly of tiny magnetic particles in external magnetic fields is important for many applications ranging from data storage to medical technologies. The development of ever smaller magnetic structures is restricted by a size limit, where the particles are just barely magnetic. For such particles we report the discovery of a kind of solution assembly hitherto unobserved, to our knowledge. The fact that the assembly occurs in solution is very relevant for applications, where magnetic nanoparticles are either solutionprocessed or are used in liquid biological environments. Induced by an external magnetic field, nanocubes spontaneously assemble into 1D chains, 2D monolayer sheets, and large 3D cuboids with almost perfect internal ordering. The self-assembly of the nanocubes can be elucidated considering the dipole-dipole interaction of small superparamagnetic particles. Complex 3D geometrical arrangements of the nanodipoles are obtained under the assumption that the orientation of magnetization is freely adjustable within the superlattice and tends to minimize the binding energy. On that basis the magnetic moment of the cuboids can be explained.M agnetic particles show an intriguing self-assembly behavior, due to mutual magnetic interactions or interaction with external magnetic fields. This can already be experienced by playing with toy magnets, which can assemble into strings or clusters. For much smaller magnetic particles, the knowledge about the magnetic assembly is crucial for technical applications involving magnetorheological fluids (1), high-density magnetic storage devices, hyperthermal cancer therapy, and magnetic resonance imaging (2). These applications use small magnetic particles, in the micrometer size range for magnetorheological fluids and down to 10 nm for magnetic resonance imaging or magnetothermal cancer therapy. Decreasing the size of the particles further decreases their magnetic moment to an extent that they are not considered in those applications anymore. In consequence, the assembly of sub-15-nm magnetic nanoparticles has been scarcely explored (3). Only recently, it was reported that cube-shaped magnetic nanoparticles of 13 nm showed a surprising magnetic-field-induced assembly into helices at the air-liquid interface (4) and 9-nm magnetic nanoparticles in the presence of a magnetic field uniquely assembled into very large, nearly defectfree monolayers and 3D cubic assemblies on solid substrates (5). This triggers the question about the arrangement of the magnetic dipoles in such assemblies where an amazing answer was recently found in the case of only eight dipoles (6), and where for larger magnetic nanoparticles and their assemblies considerable complexity was observed (7, 8).Here we report very small (sub-15-nm diameter) spherical and cube-shaped iron-oxide nanoparticles with respect to their magnetic assembly behavior. The nanoparticles are sterically stabilized by oleic acid, have very narrow size distributions, and very regular shapes (SI Appendix). The controlled synthesis of...

Precipitation of lead ions by hydrogen sulfide in the presence of amphiphilic block copoloymer micelles composed of polystyrene‐b‐poly(4)vinylpridine yields PbS nanoparticles. By adjusting the reaction conditions with respect to the lead‐to‐polymer ratio, temperature or proton concentration particles of different size (2 to 20 nm) and morphology (spheres, cubes or needles) have been prepared. These particles have been characterized by powder X‐ray diffraction and High Resolution Transmission Electron Microscopy (HRTEM). At a low lead content of the polymer micelles and relevated temperatures the formation of nanocrystalline PbS needles is preferred. These exhibit a structured absorption spectrum with two peaks at 375 and 580 nm. In polymer micelles with high lead content, PbS spheres (1 to 2 nm) are formed. Growth of these particles can be induced by increasing the proton concentration, resulting in particles with diameters up to 20 nm.

Heat-up synthesis routes are very commonly used for the controlled large-scale production of semiconductor and magnetic nanoparticles with narrow size distribution and high crystallinity. To obtain fundamental insights into the nucleation and growth kinetics is particularly demanding, because these procedures involve heating to temperatures above 300 °C. We designed a sample environment to perform in situ SAXS/WAXS experiments to investigate the nucleation and growth kinetics of iron oxide nanoparticles during heat-up synthesis up to 320 °C. The analysis of the growth curves for varying heating rates, Fe/ligand ratios, and plateau temperatures shows that the kinetics proceeds via a characteristic sequence of three phases: an induction Phase I, a final growth Phase III, and an intermediate Phase II, which can be divided into an early phase with the evolution and subsequent dissolution of an amorphous transient state, and a late phase, where crystalline particle nucleation and aggregation occurs. We extended classical nucleation and growth theory to account for an amorphous transient state and particle aggregation during the nucleation and growth phases. We find that this nonclassical theory is able to quantitatively describe all measured growth curves. The model provides fundamental insights into the underlying kinetic processes especially in the complex Phase II with the occurrence of a transient amorphous state, the nucleation of crystalline primary particles, particle growth, and particle aggregation proceeding on overlapping time scales. The described in situ experiments together with the extension of the classical nucleation and growth model highlight the two most important features of nonclassical nucleation and growth routes, i.e., the formation of intermediate or transient species and particle aggregation processes. They thus allow us to quantitatively understand, predict, and control nanoparticle nucleation and growth kinetics for a wide range of nanoparticle systems and synthetic procedures.

and morphologies, are highly promising materials for water collection, smart textiles for moisture management, dual drug release, actuation, etc.Electrospinning is a versatile method for the production of thin fibers with a high surface-to-volume-ratio from a multitude of materials in a simple and straightforward way. [4] Various fiber morphologies have been realized by either controlling the spinning parameters or by using special spinning nozzles, e.g., homogenous fibers, particles, or particles immobilized on fibers (also called beaded fibers) as well as fibers with bead-on-string or pearl-necklace morphology. [5] Beaded fibers, in which beads of different shapes (i.e., spherical, spindle shape) and the joints (fiber segment between the two beads) are made up of the same polymer, already gained an edge over conventional nanofibers in providing superhydrophobicity as well as encapsulation and release of microparticle drugs from the beads. [6] Complex fiber morphologies with precisely defined composition and properties are accessible employing special spinning nozzles, which combine two or more components in either s-b-s or core-shell (c-s) fashion. [7] This method also allows to combine bioinspired structures with appropriate material properties to achieve complex functional materials with unique properties. For example, wool-like crimps were generated by spinning polymers with different mechanical properties in an s-b-s fashion, both by melt and solution electrospinning. [7b,8] Bicomponent fibers with core-shell-type beads (coaxial beadon-string morphology) are another example. The formation of these fibers is not trivial and can be realized by using a polymer solution, which contains swollen crosslinked polymeric colloids. Applying a simple spinning nozzle produced beaded fibers, in which a row of colloidal particles is embedded in the matrix polymer. [9] Alternatively, bicomponent fibers with coaxial bead-on-string structure can be obtained by combining electrospraying with electrospinning in a coaxial electrospinning setup. [10] Similar fibers have also been produced employing a coating method. [11] In this approach, a polymer solution is coated onto a supporting fiber, which further on breaks up into droplets driven by Rayleigh instability. Fibers with coaxial beadon-string morphology are very promising materials for water harvesting applications, which demands for the development of efficient large-scale production methods. [12] Bioinspired Electrospun Bicomponent Fibers Nature is an intriguing inspiration for designing a myriad of functional materials. However, artificial mimicking of bioinspired structures usually requires different specialized procedures and setups. In this study, a new upscalable concept is presented that allows to produce two bioinspired, bicomponent fiber morphologies (side-by-side and coaxial bead-on-string) using the same electrospinning setup, just by changing the employed spinning solvent. The generated fiber morphologies are highly attractive for thermoresponsive actuat...

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