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The vast majority of nanomaterials studied in light of their ability to transmit chirality to or amplify their chirality in a surrounding medium, constitute an achiral core with chirality solely installed at the surface by conjugation or encapsulation with optically active ligands. Here we present the inverse approach focusing on surface-modified cellulose nanocrystals (CNCs) with core chirality at both the molecular and the morphological level to quantify transmission and amplification of core chirality through space using a host nematic liquid crystal (N-LC) as reporter. We find that CNCs functionalized at the surface with achiral molecules, structurally related to the N-LC, exhibit better N-LC solubility, thereby serving as highly efficient chiral inducers. Moreover, functionalization with chiral molecules only marginally enhances the efficacy of helical distortion in the host N-LC matrix, indicating the high propensity of CNCs to transfer chirality from an inherently chiral core.

This series of publications describes research rendering soft polyisobutylene (PIB)-based thermoplastic elastomers 3D printable by blending with rigid chemically compatible thermoplastics. The molecular structure, morphology, physical properties, and 3D printability of such blends have been systematically investigated. The authors' first report was concerned with the rendering of soft poly(styrene-b-isobutylene-b-styrene) (SIBS) 3D printable by blending with rigid polystyrene (PS). Here they report the macromolecular engineering of SIBS/polyphenylene oxide (PPO) blends for 3D printing. PPO, a rigid high-performance thermoplastic, is compatible with the hard PS block in SIBS; however, neither PPO nor SIBS can be directly 3D printed. The microphase-separated structures and physical properties of SIBS/PPO blends are systematically tuned by controlling blending ratios and molecular weights. Suitable composition ranges and desirable properties of SIBS/PPO blends for 3D printing are optimized. The morphology and properties of SIBS/PPO blends are characterized by an ensemble of techniques, including atomic force microscopy, small-angle X-ray scattering, and thermal and mechanical properties testing. The elucidation of processing-structure-property relationship of SIBS/PPO blends is essential for 3D printing and advanced manufacturing of high-performance polymer systems.

Transfer of chirality from an adsorbed molecule to a metal nanoparticle surface, and from the resulting chiral nanoparticle to its surroundings, depends on numerous factors - structure of the adsorbed molecule, its size and shape, and its interactions with its specific environment - but is often difficult to understand and even more difficult to measure, visualize, and quantify. We examine if chirality at the nanoscale (i.e. in gold nanoparticles capped with chiral ligand molecules) is uniquely able to generate more intense responses than their organic chiral counterparts in soft condensed matter utilizing lyotropic chromonic liquid crystals (LCLCs) forming the nematic phase. As a powerful manifestation of nanoscale chiral amplification, we show that L-cysteine capped gold nanoparticles induce a tighter chiral twist within, and similar among, stacks of nematic LCLCs with several orders of magnitude fewer chiral L- cysteine ligands in comparison to the free molecular L-amino acid.

Gold nanorods functionalized with triphenylene-based discotic liquid crystal (LC) motifs show striking self-assembly behavior both on transmission electron microscopy (TEM) grids as well as in the bulk enforced by the π–π-stacking of triphenylene groups of adjacent nanorods. TEM images confirm that these discotic LC nanorods form ribbons of parallel-stacked nanorods several hundred nanometer long. The pursued silane conjugation approach to decorate the nanorods allows for the preparation of dispersions of the nanorods in the hexagonal columnar phases of parent discotic LCs, where the nanorods can be macroscopically aligned with almost 80% efficiency by a simple shearing protocol. Doping the parent host materials with about 1% by weight of the discotic LC-capped nanorods also reduces the lattice parameter and the intracolumnar packing, which gives rise to enhanced charge carrier mobility in these hosts as determined by time-of-flight measurements.

Here we report on the modular synthesis and characterization of biodegradable, controlled porous, liquid crystal elastomers (LCE) and their use as three-dimensional cell culture scaffolds. The elastomers were prepared by cross-linking of star block-co-polymers with pendant cholesterol units resulting in the formation of smectic-A LCEs as determined by polarized optical microscopy, DSC, and X-ray diffraction. Scanning electron microscopy revealed the porosity of the as-prepared biocompatible LCEs, making them suitable as 3D cell culture scaffolds. Biodegradability studies in physiological buffers at varying pH show that these scaffolds are intact for about 11 weeks after which degradation sets in at an exponential rate. Initial results from cell culture studies indicate that these smectic LCEs are compatible with growth, survival, and expansion of cultured neuroblastomas and myoblasts when grown on the LCEs for extended time periods (about a month). These preliminary cell studies focused on characterizing the elastomer-based scaffolds' biocompatibility and the successful 3D incorporation as well as growth of cells in 60 to 150-μm thick elastomer sheets.

Chemically and thermally robust liquid crystal silane-functionalized gold nanoparticles (i.e. AuNP1-AuNP3) were synthesized through silane conjugation. Colloidal dispersions of these particles with mesogenic ligands that are structurally identical (as in AuNP1, AuNP2) or compatible (as in AuNP3) with molecules of the nematic liquid crystal (N-LC) host showed superior colloidal stability and dispersibility. The thermal, optical, and electro-optic behaviors of the N-LC composites at different concentrations of each gold nanoparticle were investigated. All dispersions showed lower values for the rotational viscosity and elastic constant, but only AuNP3 with a dissimilar structure between the nanoparticle ligand and the host displayed the most drastic thermal effects and overall strongest impact on the electro-optic properties of the host. The observed results were explained considering both the structure and the density of the surface ligands of each gold nanoparticle.

Doping nematic liquid crystals with small amounts of nanoparticles can significantly alter the electro-optic response of the nematic host. Some of these effects result from nanoparticles influencing the liquid crystal/substrate interface, while other effects are caused by nanoparticles in the bulk. So far, little attention has been paid to the influence of surface interactions on the determination of bulk properties. In the present study, these effects are investigated experimentally and confirmed by numerical simulations. The splay-type Fréedericksz-transition of the nematic liquid crystal 5CB doped with CdSe quantum dots is investigated, as these dispersions are known from earlier studies to affect the initial alignment layers. In comparison, dispersions of chemically and thermally stable silanized gold nanoparticles in the apolar nematic host FELIX-2900-03 are analyzed, which are expected to be bulk-active only. A data fitting routine is presented which allows a distinction between bulk and surface effects of nanoparticle doping. For the quantum dots, an increase of pretilt angle proportional to the doping concentration is found, as well as a slight decrease of the anchoring energy of molecules at the confining substrates. The silanized gold particles show no influence on the boundary conditions up to doping concentrations of 2.5 % (w). For higher concentrations an increase of pretilt angle is reported.

Ink-jet printing of monolayer-capped gold nanoparticles is introduced as a versatile and highly efficient means to pattern the alignment of nematic liquid crystals. Any homeotropic alignment patterns can be created quickly ranging in size from 30 μm (850 dpi) to several square inches, with high accuracy that does not deteriorate with time. Depending on the alignment underlayer, intermediate configurations between homeotropic and homogeneous are also feasible. Nematic liquid crystals with both positive and negative dielectric anisotropy can be switched by applying a DC or AC electric field in the printed vertical domains with the substrate configuration determining the electro-optic response.

Fascinating nematic- and smectic-like self-assembled arrays are observed for gold nanorods partially capped with either laterally or terminally attached nematic liquid crystals upon slow evaporation of an organic solvent on TEM grids. These arrays can be manipulated and reoriented by applying an external magnetic field from quasi-planar to vertical similar to a Freedericksz transition of common organic nematic liquid crystals. Birefringence and thin film textures of these self-assembled gold nanorod arrays observed by polarized optical microscopy are strongly reminiscent of common organic nematic liquid crystal textures between crossed polarizers and, additionally, support the formation of ordered liquid crystal-like anisotropic superstructures. The ordering within these arrays is also confirmed in bulk samples using small angle X-ray scattering (SAXS).

A biocompatible, reliable, and particularly versatile synthesis of magnetic iron oxide nanoparticles (IONPs) is presented that uses iron(III) acetylacetonate Fe(acac) 3 as an iron precursor and sodium borohydride as a reducing agent. Both the reaction temperature and the concentration of the reducing agent have considerable effects on the IONP size. These dependencies can be used to prepare IONPs ranging in size from 5 to 8 nm, as determined by transmission electron microscopy (TEM). Synthesis at room temperature or with higher sodium borohydride concentrations always resulted in smaller particle sizes. Powder X-ray diffraction patterns show the presence of an iron oxide phase with a cubic unit cell and allow for the determination of the lattice parameters and average crystallite sizes for all synthesized IONPs. Transmission Mossbauer spectroscopy shows that the as-synthesized IONPs are pure magnetite (Fe 3 O 4 ) and is further used to elucidate the reaction pathway by analyzing iron intermediates formed prior to nanoparticle formation and precipitation. TEM and high-resolution TEM reveal quasi-spherical shapes and lattice fringes for most IONPs. With only minor modifi cations of the synthesis procedure, this versatile, one-pot synthesis is proven to be suitable for the production of bare (uncoated) IONPs, IONPs with hydrophilic poly(ethylene glycol), L -arginine, and L -glutamic acid coatings, as well as IONPs with hydrophobic coatings such as oleic acid. All coated IONPs were characterized by FT-IR spectroscopy. In addition, the bare IONPs could easily be modifi ed post-synthesis with a suitable capping agent using ultrasonication. To verify the biocompatibility of the IONPs, in vitro cytotoxicity studies were carried out on bare IONPs with intestinal (Caco2) and liver epithelial (HepG2) cell cultures using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Phase contrast microscopy after hematoxylin-eosin staining showed the intact morphology of the Caco2 and HepG2 cells treated with IONPs.

We demonstrate that alkylthiol-capped gold nanoclusters doped into nematic liquid crystals (N-LCs) with positive dielectric anisotropy give rise to an unprecedented dual alignment mode and electro-optical response, which has a potential impact on current liquid crystal (LC) display technologies and N-LC optical-biosensor design. By fine-tuning experimental conditions (temperature, electric field, and alignment), N-LCs doped with gold nanoclusters can be aligned and electrically reoriented either like N-LCs with a positive dielectric anisotropy in a planar cell or, alternatively, as N-LCs with a negative dielectric anisotropy in a homeotropic cell, both at lower threshold voltages than the pure N-LC.

Molecular self-organization, driven by attractive face-to-face interactions between 1 and 2,4,7-trinitrofluorenone, leads to the formation of an optically biaxial smectic A liquid crystalline phase-a long-predicted new state of ordered soft matter.

On p. 212, Torsten Hegmann and co-workers describe nematic liquid crystals (N-LCs) confined in planar liquid crystal cells after doping with small quantities of gold nanoclusters. These give rise to a dual alignment mode and electro-optic response (Freedericksz transition). By fine-tuning of experimental conditions, N-LCs doped with gold nanoclusters can be electrically reoriented and aligned either like N-LCs with a positive dielectric anisotropy (used in twisted nematic displays) in a planar cell or alternatively as N-LCs with a negative dielectric anisotropy (used in large LCD TVs based on the vertical alignment mode). We demonstrate that alkylthiol-capped gold nanoclusters doped into nematic liquid crystals (N-LCs) with positive dielectric anisotropy give rise to an unprecedented dual alignment mode and electro-optical response, which has a potential impact on current liquid crystal (LC) display technologies and N-LC optical-biosensor design. By fine-tuning experimental conditions (temperature, electric field, and alignment), N-LCs doped with gold nanoclusters can be aligned and electrically reoriented either like N-LCs with a positive dielectric anisotropy in a planar cell or, alternatively, as N-LCs with a negative dielectric anisotropy in a homeotropic cell, both at lower threshold voltages than the pure N-LC.

A biocompatible, reliable, and particularly versatile synthesis of magnetic iron oxide nanoparticles (IONPs) is presented that uses iron(III) acetylacetonate Fe(acac)3 as an iron precursor and sodium borohydride as a reducing agent. Both the reaction temperature and the concentration of the reducing agent have considerable effects on the IONP size. These dependencies can be used to prepare IONPs ranging in size from 5 to 8 nm, as determined by transmission electron microscopy (TEM). Synthesis at room temperature or with higher sodium borohydride concentrations always resulted in smaller particle sizes. Powder X-ray diffraction patterns show the presence of an iron oxide phase with a cubic unit cell and allow for the determination of the lattice parameters and average crystallite sizes for all synthesized IONPs. Transmission Mossbauer spectroscopy shows that the as-synthesized IONPs are pure magnetite (Fe3O4) and is further used to elucidate the reaction pathway by analyzing iron intermediates formed prior to nanoparticle formation and precipitation. TEM and high-resolution TEM reveal quasi-spherical shapes and lattice fringes for most IONPs. With only minor modifications of the synthesis procedure, this versatile, one-pot synthesis is proven to be suitable for the production of bare (uncoated) IONPs, IONPs with hydrophilic poly(ethylene glycol), L-arginine, and L-glutamic acid coatings, as well as IONPs with hydrophobic coatings such as oleic acid. All coated IONPs were characterized by FT-IR spectroscopy. In addition, the bare IONPs could easily be modified post-synthesis with a suitable capping agent using ultrasonication. To verify the biocompatibility of the IONPs, in vitro cytotoxicity studies were carried out on bare IONPs with intestinal (Caco2) and liver epithelial (HepG2) cell cultures using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Phase contrast microscopy after hematoxylin-eosin staining showed the intact morphology of the Caco2 and HepG2 cells treated with IONPs.