Elongated PEO-based nanoparticles bind the high-density lipoprotein (HDL) receptor scavenger receptor class B I (SR-BI).

Targeting cell-surface receptors with nanoparticles (NPs) is a crucial aspect of nanomedicine. Here, we show that soft, flexible, elongated NPs with poly-ethylene-oxide (PEO) exteriors and poly-butadiene (PBD) interiors - PEO-PBD filomicelles - interact directly with the major high-density lipoprotein (HDL) receptor and SARS-CoV-2 uptake factor, SR-BI. Filomicelles have a ~ 6-fold stronger interaction with reconstituted SR-BI than PEO-PBD spheres. HDL, and the lipid transport inhibitor, BLT-1, both block the uptake of filomicelles by macrophages and Idla7 cells, the latter are constitutively expressing SR-BI (Idla7-SR-BI). Co-injections of HDL and filomicelles into wild-type mice reduced filomicelle signal in the liver and increased filomicelle plasma levels. The same was true with SCARB1-/- mice. SR-BI binding is followed by phagocytosis for filomicelle macrophage entry, but only SR-BI is needed for entry into Idla7-SR-BI cells. PEO-PBD spheres did not interact strongly with SR-BI in the above experiments. The results show elongated PEO-based NPs can bind cells via cooperativity among SR-BI receptors on cell surfaces.

Single-step process to improve the mechanical properties of carbon nanotube yarn.

Carbon nanotube (CNT) yarns exhibit low tensile strength compared to conventional high-performance carbon fibers due to the facile sliding of CNTs past one another. Electron beam (e-beam) irradiation was employed for in a single-step surface modification of CNTs to improve the mechanical properties of this material. To this end, CNT yarns were simultaneously functionalized and crosslinked using acrylic acid (AA) and acrylonitrile (AN) in an e-beam irradiation process. The chemical modification of CNT yarns was confirmed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and scanning electron microscopy (SEM). The best improvement in mechanical properties was achieved on a sample treated with an aqueous solution of AA and subsequent irradiation. CNT yarn treatment with AA enhanced the strength (444.5 ± 68.4 MPa) by more than 75% and the modulus (21.5 ± 0.6 GPa) by more than 144% as compared to untreated CNT yarn (strength 251 ± 26.5 MPa and modulus 8.8 ± 1.2 GPa).

Metal/Ion Interactions Induced p-i-n Junction in Methylammonium Lead Triiodide Perovskite Single Crystals.

Hybrid perovskites, as emerging multifunctional semiconductors, have demonstrated dual electronic/ionic conduction properties. We report a metal/ion interaction induced p-i-n junction across slightly n-type doped MAPbI3 single crystals with Au/MAPbI3/Ag configuration based on interface dependent Seebeck effect, Hall effect and time-of-flight secondary ion mass spectrometry analysis. The organic cations (MA+) interact with Au atoms, forming positively charged coordination complexes at Au/MAPbI3 interface, whereas iodine anions (I-) can react with Ag contacts, leading to interfacial ionic polarization. Such metal/ion interactions establish a p-doped region near the Au/MAPbI3 interface due to the formation of MA+ vacancies, and an n-doped region near the Ag/MAPbI3 interface due to formation of I- vacancies, consequently forming a p-i-n junction across the crystal in Au/MAPbI3/Ag configuration. Therefore, the metal/ion interaction plays a role in determining the surface electronic structure and semiconducting properties of hybrid perovskites.

Improving mechanical properties of carbon nanotube fibers through simultaneous solid-state cycloaddition and crosslinking.

Individual carbon nanotubes (CNTs) exhibit exceptional mechanical properties. However, difficulties remain in fully realizing these properties in CNT macro-assemblies, because the weak inter-tube forces result in the CNTs sliding past one another. Herein, a simple solid-state reaction is presented that enhances the mechanical properties of carbon nanotube fibers (CNTFs) through simultaneous covalent functionalization and crosslinking. This is the first chemical crosslinking proposed without the involvement of a catalyst or byproducts. The specific tensile strength of CNTFs obtained from the treatment employing a benzocyclobutene-based polymer is improved by 40%. Such improvement can be attributed to a reduced number of voids, impregnation of the polymer, and the formation of covalent crosslinks. This methodology is confirmed using both multiwalled nanotube (MWNT) powders and CNTFs. Thermogravimetric analysis, differential scanning calorimetry, x-ray photoelectron spectroscopy, and transmission electron microscopy of the treated MWNT powders confirm the covalent functionalization and formation of inter-tube crosslinks. This simple one-step reaction can be applied to industrial-scale production of high-strength CNTFs.

Block Copolymers: Synthesis, Self-Assembly, and Applications.

Research on block copolymers (BCPs) has played a critical role in the development of polymer chemistry, with numerous pivotal contributions that have advanced our ability to prepare, characterize, theoretically model, and technologically exploit this class of materials in a myriad of ways in the fields of chemistry, physics, material sciences, and biological and medical sciences. The breathtaking progress has been driven by the advancement in experimental techniques enabling the synthesis and characterization of a wide range of block copolymers with tailored composition, architectures, and properties. In this review, we briefly discussed the recent progress in BCP synthesis, followed by a discussion of the fundamentals of self-assembly of BCPs along with their applications.

Unexpected Molecular Weight Effect in Polymer Nanocomposites.

The properties of the interfacial layer between the polymer matrix and nanoparticles largely determine the macroscopic properties of polymer nanocomposites (PNCs). Although the static thickness of the interfacial layer was found to increase with the molecular weight (MW), the influence of MW on segmental relaxation and the glass transition in this layer remains to be explored. In this Letter, we show an unexpected MW dependence of the interfacial properties in PNC with attractive polymer-nanoparticle interactions: the thickness of the interfacial layer with hindered segmental relaxation decreases as MW increases, in sharp contrast to theoretical predictions. Further analyses reveal a reduction in mass density of the interfacial layer with increasing MW, which can elucidate these unexpected dynamic effects. Our observations call for a significant revision of the current understandings of PNCs and suggest interesting ways to tailor their properties.

Synthesis and photoluminescent properties of geometrically hindered cis-tris(diphenylaminofluorene) as precursors to light-emitting devices.

A novel highly luminescent tris-fluorenyl ring-interconnected chromophore tris(DPAF-C9) was synthesized using a C3 symmetrical triaminobenzene core as the synthon. This structure bears three light-harvesting 2-diphenylamino-9,9-dialkylfluorenyl (DPAF) ring moieties with each attached by two branched 3',5',5'-trimethylhexyl (C9) arms. A major stereoisomer was chromatographically isolated and characterized to possess a 3D structural configuration of cis-conformer in a cup-form. Molecular calculation at B3LYP/6-31G* level revealed the unexpected stability of this cis-cup-conformer of tris(DPAF-C9) better than that of the stereoisomer in a propeller-form and the trans-conformer. The structural geometry is proposed to be capable of minimizing the aggregation related self-quenching effect in the condensed phase. Fluorescence emission wavelength of tris(DPAF-C9) was found to be in a close range to that of PVK that led to its potential uses as the secondary blue hole-transporting material for enhancing the device property toward the modulation of PLED performance.

CdS/C60 binary nanocomposite films prepared via phase transition of PS-b-P2VP block copolymer.

We demonstrate the well-defined control of phase transition of a polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer from spherical micelles to lamellar structures, in which CdS and C60 nanoparticles (NPs) are selectively positioned at the P2VP domains. The CdS NPs are in situ synthesized using PS-b-P2VP block copolymer templates that are self-assembled in PS-selective solvents. The CdS-PS-b-P2VP micellar structures are transformed to lamellar phase by adjusting a solvent selectivity for both blocks. In addition, a binary system of CdS/C60 embedded in PS-b-P2VP lamellar structures (CdS/C60-PS-b-P2VP) is fabricated by embedding C60 molecules into P2VP domain though charge-transfer complexation between pyridine units of PS-b-P2VP and C60 molecules. The CdS/C60-PS-b-P2VP nanostructured films are characterized by transmission electron microscopy (TEM) and UV-Vis spectrometer.

Hollow flower micelles from a diblock copolymer.

A poly(2-vinylpyridine)-block-poly(2-(4-vinylphenyl)pyridine) (P2VP106-b-PVPPy95) coil-coil diblock copolymer forms hollow flower micelles in a mixed solvent of methanol and water (95/5, v/v) in a one step process. The geometry and composition of the micelles allow formation of a Pt-Au bimetallic dendritic nanocatalyst with a Pt leaf at room temperature.

Molecular level ordering in poly(2-vinylpyridine).

The reaction between atactic poly(2-vinylpyridine) and 1,4-dibromobutane leads to formation of long-range 3D molecular ordering in polymer chains mainly because the side group (pyridine) of the polymer chain changes to a syndotactic configuration. This may enable the production of functional molecular devices that operate on a 3D atomic scale.

Uni-molecular hollow micelles from amphiphilic homopolymer poly(2-(4-vinylphenyl)pyridine).

Amphiphilic homopolymer poly(2-(4-vinylphenyl)pyridine) (PVPPy) forms hollow micelles with uni-molecular thickness in a tetrahydrofuran/water (95/5 v/v) azeotropic solvent. Depending on the pH of the media, the micelles may be transformed to vesicles.

Programmable bipolar and unipolar nonvolatile memory devices based on poly(2-(N-carbazolyl)ethyl methacrylate) end-capped with fullerene.

A novel polymer, poly(2-(N -carbazolyl)ethyl methacrylate) end-capped with fullerene (PCzMA-C(60) ), has been synthesized via living anionic polymerization. Electrically programmable flash memory devices were easily fabricated with this polymer by using solution coating and metal deposition. This polymer was found in these devices to exhibit bipolar and unipolar switching behaviors with a high ON/OFF current ratio, a long retention time, high reliability, and low power consumption. The excellent properties and easy processability of this polymer open up the possibility of the mass production of high performance nonvolatile memory devices at low cost.

Well-Defined Ambipolar Block Copolymers Containing Monophosphorescent Dye.

Well-defined ambipolar block copolymers containing carbazole, oxadiazole moieties, and only one homoleptic iridium(III) complex between the carbazole and oxadiazole blocks were successfully synthesized by sequential living anionic polymerization with controlled molecular weights (Mw), a narrow molecular weight distribution (Mw/Mn < 1.15), and a high conversion yield (98-100%). The optimum conditions for the successful controlled synthesis of an oxadiazole-containing the homopolymer of poly(2-phenyl-5-(6-vinylpyridin-3-yl)-1,3,4-oxadiazole) have been established by controlling the nucleophilicity strength of the carbanion. In addition, the location and concentration of the homoleptic iridium(III) complex were controlled by linking it to 1,1-diphenylethylene, which exhibits monoaddition characteristics in the main chain of the block copolymer.

Structural and electrical characterization of a block copolymer-based unipolar nonvolatile memory device.

Electronic devices based on a series of synthesized block copolymers are demonstrated. In particular, a block copolymer system with a lamellar structure exhibits unipolar switching behavior. This study provides a simple strategy based on the adjustment of the block ratio in block copolymers to control the polymer morphology and thus the electrical and switching properties of polymer-based memory devices.

Effect of solvent composition on transformation of micelles to vesicles of rod-coil poly(n-hexyl isocyanate-block-2-vinylpyridine) diblock copolymers.

The self-aggregation behavior of an amphiphilic rod-coil block copolymer of poly(n-hexyl isocyanate-block-2-vinylpyridine) (PHIC(189)-b-P2VP(228)) (f(P2VP) = 0.78, M(n) = 24.5K) in a tetrahydrofuran (THF)/water system was examined using dynamic light scattering (DLS), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM). The presence of a certain amount of water in the THF-based polymer solution induced a morphological transition from spherical solid micelles to open mouth platelike vesicles. The size of the aggregates increased with an increase in water content in the mixed solvent of THF/water. In the range of 30-40% water, the polymer formed vesicles with an interdigitated architecture of poly(n-hexyl isocyanate) (PHIC) at the center of the membrane and with the poly(2-vinylpyridine) (P2VP) block forming the outer layers and pointing toward the solvent. However, at higher water contents, the thickness of the bilayer increased due to the rearrangement of the vesicle membrane from a flip-flop to a lamellar architecture. After the degradation of the PHIC from the vesicles at basic pH, hollow spherical aggregates remained stable. After removing the THF from the mixed solvent using dialysis, large-sized compound vesicles were formed.

The fabrication of nanopatterns with Au nanoparticles-embedded micelles via nanoimprint lithography.

We fabricated nanopatterns with Au nanoparticles-embedded micelles (Au-micelles) by self-assembly of block copolymers via nanoimprint lithography. The micelle structure prepared by self-assembled block copolymers was used as a template for the synthesis of Au nanoparticles (Au NPs). Au NPs were synthesized in situ inside the micelles of polystyrene-block-poly(2-vinylpyridine) (PS- b-P2VP). Au-micelles were arranged on the trenches of the polymer template, which was imprinted by nanoimprint lithography. The fabrication of line-type and dot-type nanopatterns was carried out by the combined method. In addition, multilayer nanopatterns of the Au-micelles were also proposed.

Nonaqueous nanoscale metal transfer by controlling the stickiness of organic film.

Nanoscale metal patterns were successfully reproduced on top of a functional organic layer by a direct metal-transfer technique (DMT). A gold film deposited on the protruding features of a stamp was transferred to the organic layer by controlling its stickiness through a two-step thermal treatment. The process was also suitable for the transfer of highly adhesive metal materials to the stamp surface by using an additional gold layer. Chromium nanowires at 70 nm half-pitch were faithfully produced without any damage to the organic active layer.

Fabrication of an open Au/nanoporous film by water-in-oil emulsion-induced block copolymer micelles.

Water-in-oil (W/O) emulsion-induced micelles with narrow size distributions of approximately 140 nm were prepared by sonicating the polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer in the toluene/water (50:1 vol %). The ordered nanoporous block copolymer films with the hydrophilic P2VP interior and the PS matrix were distinctly fabricated by casting the resultant solution on substrates, followed by evaporating the organic solvent and water. The porous diameter was estimated to be about 70 nm. Here, we successfully prepared the open nanoporous nanocomposites, the P2VP domain decorated by Au (5+/-0.4 nm) nanoparticles based on the methodology mentioned. We anticipate that this novelty enhances the specific function of nanoporous films.

Location control of Au/CdS nanoparticles in block copolymer micelles.

Micellar core-embedded Au or CdS nanoparticles (NPs), in which the number of NPs was controlled by a solid type or a solution type of metallic precursors and by their amounts, were constructed using a block copolymer as a template. The location of NPs located at the micellar core was dramatically changed to the corona by the solvent-induced micellar core-corona inversion. By mixing the synthetic methods demonstrated, harmonious Au/CdS NPs with different particle sizes, numbers, and positions in the micellar core were also prepared.