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A facile route to fabricate size-tunable superparamagnetic/polymeric core/shell nanoparticles with uniform distribution was introduced based on metal-free atom transfer radical polymerization at ambient temperature.

The ON/OFF ratio and long-term stability are two important issues for flexible organic-inorganic hybrid perovskite (OHP) resistive random access memory (RRAM) for practical applications. In this work, polyvinylammonium (PVAm) is applied to partially replace methylamine ions (MA

Photocatalytic CO

A silane based AIE probe (APTS-TPE) was prepared through the incorporation of (3-Aminopropyl)triethoxysilane (APTS) and tetraphenylethylene (TPE), and applied for in-situ visual monitoring of the silica growth in Stober process. The TPE groups in the APTS-TPE structure can be anchored in the -Si-O-Si- molecular network and exhibited strong fluorescence emission owing to the restriction of intramolecular motion of TPE group. Real-time in-situ particles size analysis and photoluminescence (PL) intensity analysis were carried out to follow the evolution of PL intensity with particle size. The relationship between silica size and PL intensity in parallel experiments were also discussed. Compared with traditional characterization methods, this method has the potential application for silica industrial production and fundamental research, with the advantage of sensitive, rapid and non-invasive.

An unconventional but robust strategy to fabricate uniform hybrid inorganic–organic core–shell superparamagnetic magnetite (Fe3O4) colloidal nanoclusters in situ was introduced based on water-soluble multi-arm star-shaped brush-like block copolymers as multifunctional polymeric nanoreactors, composed of poly(ethylene oxide) (PEO) as the main chain, poly(acrylic acid) (PAA) as functional graft chains, and the second PEO block as a shell (i.e., multi-arm star-shaped brush-like block copolymer [(PEO-g-PAA)-b-PEO]18) with different molecular weights and grafting densities. FeCl3 and FeCl2 as precursors of Fe3O4 were loaded into the graft chain PAA template domain of a multi-arm star-shaped brush-like block copolymer [(PEO-g-PAA)-b-PEO]18 polymeric nanoreactors, followed by an in situ reaction to form Fe3O4 nanoclusters. The dimensions of the clusters can be tuned precisely by changing the chain lengths of the PEO backbones of the PAA grafting region. In addition, the density of the subunits can also be tailored by adjusting grafting density of the PAA side chains, determined by the molar ratio of ethoxyethyl glycidyl ether (EEGE) to EO during the anionic copolymerization. The Fe3O4 colloidal nanocrystal clusters with superparamagnetic behavior at room temperature are highly water-dispersed because of the hydrophilic ligands of the surface-tethered PEO polymer shell.

An unconventional but robust route to fabricate highly pure α-Al2O3 colloidal nanocrystals with tunable surface chemistry and dimensions was introduced based on semi-aromatic polyamide (PA6Py) with pyridine rings as a functional matrix. The surface ligands of α-Al2O3 nanocrystals can be tuned by choosing different carboxyl-terminated polymers (e.g., PS and PEO).

Although polyamide-co-polyether, the most important co-polyamide species, has achieved big success, the inadequate biocompatibility still restricts it further application in biomedical area. In this paper, polydimethylsiloxane (PDMS) segment is introduced into copolymer to replace polyether segment, which is intended to fulfill the copolymer with improved surface performance. Two prepolymer condensation process was used to synthesis the novel PA1212-b-PDMS series, which is constructed by PDMS flexible segment (Mn = 1000 g/mol) and PA1212 rigid segment (Mn = 1000, 3000, 5000, 7000, 10,000 g/mol). FTIR and 1H NMR were carried out to evidence the success of the copolymerization and verify the chemical structure. Melting and crystallization behavior, thermal stability, and crystal structure of the series were characterized by DSC, TG and XRD, respectively. To explore the potential usage of the copolymers, mechanical properties were thoroughly investigated. The series possess tunable toughness and rigidity corresponding to different chain compositions. When Mn of PA1212 segment is above 5000 g/mol, the copolymer presents typical tough and stiff feature with an ultimate elongation rate of around 500% and a fair tensile strength around 35 MPa. More than that, the platelet adhesion and activation test was conducted to estimate the biocompatibility of the polymers. The contact angel goniometry and XPS were further utilized to understand their surface performance. The as-prepared copolymers give distinct-different performance from homo-polyamide and polyamide-co-polyether. Barely cell adhesion on the surface indicates the greatly improved biocompatibility achieved by the series, which promises the mechanical-property-adjustable novel co-polyamide a broad prospect in biomedical area.

A simple one-pot double in-situ synthetic method was proposed to fabricate transparent semi-aromatic polyamides (SAPA) nanocomposites with upconversion nanoparticles (UCNP) as nanophase contents by combining hydrothermal method with melt polycondensation method. The key to this method is that the nanoparticles and polyamides were prepared in one-pot by simply mixing polyamides monomers and UCNP precursors as the raw materials without preparing polyamides or nanoparticles in advance. This approach enables the simple fabrication of transparent upconversion luminescent semi-aromatic polyamides nanocomposites with UCNP uniformly dispersed and can be extend to other kinds of polyamides and functional nanoparticles to prepare various polyamide nanocomposites.

Photo-induced metal free ATRP method was employed for the synthesis of star-shaped polymers. By using 21-Br-β-CD as the macroinitiator, 10-phenylphenothiazine as the photoredox catalyst, star-shaped PtBA homopolymers were synthesized. The photo-induced ATRP displayed all the characteristics of controlled/living polymerization systems and the good light control over the polymerization process. The successful chain extension with MMA demonstrated the high livingness of PtBA “arms” and good controllability of the Photo-induced metal free ATRP. Finally, the achieved PtBA-b-PMMA star-shaped copolymers were used as templates for the preparation of precisely size-tunable CdSe quantum dots after a simple hydrolyzing process.

Although lots of works have been done on the hydrolysis of synthetic biodegradable polymers, the methods for monitoring the degradation process still suffer from some disadvantages, especially in terms of detection speed and non-invasive manners. In this work, a fast, non-invasive visualization monitoring platform was developed for hydrolytic degradation of bio-degradable polymers based on aggregation-induced emission (AIE) technique. We synthesized and introduced an amphiphilic AIE probe to the commercial polylactide (PLA) matrix through a simple co-precipitation process. Amphiphilic AIE probes gradually entered the aqueous media during the hydrolytic degradation process of PLA matrix, which exhibited fluorescence evolution. The variation of fluorescence emission corresponding to the evolution of PLA mass loss could be easily observed by naked eyes. Compared to traditional characterization techniques based on mass loss and molar mass measurements by sampling, this method is sensitive, fast and non-invasive, and has the potential to become a standard method for commercial bio-degradable product testing.

Despite significant works for monitoring the homogeneous polymerization system, the monitoring of heterogeneous polymerization process (e.g. emulsion polymerization) with aggregation-induced emission (AIE) technique still remains a challenge. Herein, we first synthesized amphiphilic poly (ethylene oxide) methyl ether methacrylate (PEGMA) based AIE probe which was then used for the monitoring of conventional emulsion polymerization process. The classic polymerization mechanism and different stages of emulsion polymerizations were relived from the viewpoint of fluorescence emission. The movement of AIE probes in the three phases of emulsions during the polymerization process and the swelling effect on fluorescence emission have been discussed thoroughly. We believe this work can promote the application of AIE technique in on-line visual monitoring for emulsion polymerization industry and fundamental research.

Based on the electrostatic interaction, prepared γ-Fe2O3 nanoparticles with high positive charges (+ 45 mv) were modified by negative charged ligninsulfonate (LS, - 34 mv) to synthensize LS/γ-Fe2O3 composite. LS is low-price, environmentally friendly and renewable biomacromolecule. The LS/γ-Fe2O3 composite were applied in a Pickering miniemulsion polymerization as the only stabilizer, without any auxiliary comonomers and surfactants. The surface anchored γ-Fe2O3 induced the formation of strawberry-like hybrid latex particles who were endowed with superparamagnetic functional properties. Furthermore, the effect of the ratios of LS to γ-Fe2O3 on the stability of the LS/γ-Fe2O3 composites was investigated. The content of γ-Fe2O3 in the LS/γ-Fe2O3 composites should be lower than 66.7 wt%, or the stability of the Pickering miniemulsion polymerization would be destroyed, owing to the charge neutralization behavior of the LS and γ-Fe2O3. Within this range, the latex particle size increased with the increasing of γ-Fe2O3 content.

Programmable photoactuation enabled by graphene: Graphene sheets aligned in liquid crystalline elastomers are capable of absorbing near-infrared light. They thereafter act as nanoheaters and provide thermally conductive pathways to trigger the nematic-to-isotropic transition of elastomers, leading to macroscopic mechanical deformation of nanocomposites. Large strain, high actuation force, high initial sensitivity, fast reversible response, and long cyclability are concurrently achieved in nanocomposites.

Organic-inorganic nanocomposites composed of polymers and nanoparticles offer a vast design space of potential material properties, depending heavily on the properties of these two constituents and their spatial arrangement. The ability to place polymers in direct contact with functional nanoparticles via strong bonding, that is, stable chemical interaction without the dissociation of surface capping polymers, provides a means of preventing nanoparticles from aggregation and increasing their dispersibility in nanocomposites, and promises opportunities to explore new properties and construction of miniaturized devices. However, this is still a challenging issue and has not yet been largely explored. Here, we report an unconventional strategy to create in situ organic-inorganic nanocomposites comprising monodisperse ferroelectric nanoparticles directly and permanently tethered with ferroelectric polymers by capitalizing on rationally designed amphiphilic star-like diblock copolymer as nanoreactors. The diameter of ferroelectric nanoparticles and the chain length of ferroelectric polymers can be precisely tuned. The dielectric and ferroelectric properties of nanocomposites containing different sizes of ferroelectric nanoparticles were scrutinized. Such bottom-up crafting of intimate organic-inorganic nanocomposites offers new levels of tailorability to nanostructured materials and promises new opportunities for achieving exquisite control over the surface chemistry and properties of nanocomposites with engineered functionality for diverse applications in energy conversion and storage, catalysis, electronics, nanotechnology, and biotechnology.

Star-like amphiphilic triblock copolymers were rationally designed and synthesized by combining two sequential atom-transfer radical polymerization reactions with a click reaction. Subsequently, a family of uniform magnetic/plasmonic core/shell nanoparticles was crafted by capitalizing on these triblock copolymers as nanoreactors. The diameter of the magnetic core and the thickness of the plasmonic shell could be independently and accurately controlled by varying the molecular weights (i.e., the chain lengths) of the inner and intermediate blocks of the star-like triblock copolymers, respectively. The surface plasmonic absorption of core/shell nanoparticles with different core diameters and shell thicknesses was systematically studied and theoretically modeled. This robust strategy provides easy access to a large variety of multifunctional nanoparticles with large lattice mismatches for use in optics, optoelectronics, catalysis, or bioimaging.

Atom transfer radical polymerization (ATRP) of 4-vinylpyridine, t-butyl acrylate, and styrene in sequential order from a β-cyclodextrin core yielded an amphiphilic star-like triblock copolymer, poly(4-vinylpyridine)-block-poly(t-butyl acrylate)-block-polystyrene (P4VP-b-PtBA-b-PS). Subsequently, star-like triblock copolymer composed of inner hydrophilic P4VP blocks, central hydrophobic PtBA blocks, and outer hydrophobic PS blocks with well-defined molecular architecture and molecular weight of each block was judiciously exploited as nanoreactor for synthesis of precisely shaped hairy plasmonic/semiconductor Au/TiO2 core/shell nanoparticles. The resulting Au/TiO2 nanoparticles were intimately and permanently tethered with outer PS chains that enabled the superior solubility of nanoparticles in nonpolar solvents. The PS chains on the surface of these bifunctional nanoparticles were carbonized by annealing in an inert atmosphere (i.e., yielding carbon-coated Au/TiO2 nanoparticles). In comparison to a widely ...

We developed an unconventional route to produce uniform and intimately contacted semiconducting organic-inorganic nanocomposites for potential applications in thermoelectrics. By utilizing amphiphilic star-like PAA-b-PEDOT diblock copolymer as template, monodisperse PEDOT-functionalized lead telluride (PbTe) nanoparticles were crafted via the strong coordination interaction between PAA blocks of star-like PAA-b-PEDOT and the metal moieties of precursors (i.e., forming PEDOT-PbTe nanocomposites). As the inner PAA blocks are covalently connected to the outer PEDOT blocks, the PEDOT chains are intimately and permanently tethered on the PbTe nanoparticle surface, thereby affording a well-defined PEDOT/PbTe interface, which prevents the PbTe nanoparticles from aggregation, and more importantly promotes the long-term stability of PEDOT-PbTe nanocomposites. We envision that the template strategy is general and robust, and offers easy access to other conjugated polymer-inorganic semiconductor nanocomposites for use in a variety of applications.

A viable strategy for uniform organo-silica hybrid nanoparticles and nanocapsules was developed. The key to our strategy is the implementation of spherical star-like homopolymers and diblock copolymers with well-controlled molecular weights that form unimolecular micelles in solution as nanoreactors. Organo-silica hybrid nanoparticles were crafted by introducing trimethoxysilyl functionalities to the arm of star-like homopolymers. Quite intriguingly, organo-silica hybrid nanocapsules with an interior cavity were created when the trimethoxysilyl moieties were incorporated into the outer block of star-like diblock copolymers. The diameter of hybrid nanoparticles and the shell thickness of hybrid nanocapsules can be readily tailored via the living polymerization of star-like homopolymer and diblock copolymer nanoreactors, respectively. These hybrid nanoparticles and nanocapsules may find promising applications in polymer nanocomposites, water purification, separation, catalysis, and drug delivery. We envision that the nanoreactor strategy is general and robust. By rationally designing nonlinear yet structurally regular polymers possessing metal-containing units, other exotic metal- and metal oxide-containing nanostructures can also be easily accessed for a variety of applications.

A series of novel water-soluble multi-arm star-shaped brush-like block copolymers, composed of poly(ethylene oxide) (PEO) as the main chain, poly(acrylic acid) (PAA) as functional graft chains, and a second PEO block as the shell (i.e., multi-arm star-shaped brush-like block copolymer (PEO-g-PAA)-b-PEO) with different molecular weights and grafting density, were rationally designed and synthesized by a combination of anionic copolymerization and atom transfer radical polymerization (ATRP). The anionic ring-opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was conducted first by using α-cyclodextrin (α-CD) with 18 hydroxyl groups and diphenylmethyl sodium (DPMNa) as co-initiator system. The monomer reactivity ratios for EO and EEGE were also determined: r1(EO) = 1.18 ± 0.03 and r2(EEGE) = 0.79 ± 0.01, respectively. Then the resulting multi-arm star-shaped copolymers of poly(EO-co-EEGE) with hydroxyls as end functional groups were utilized as star-shaped macroinitiators to sequentially initiate the anionic ring-opening polymerization of monomer EO for the second block hydrophilic homopolymer PEO chain grown on the first block poly(EO-co-EEGE) arm end, and then the ethoxyethyl groups of the star-shaped block copolymers of poly(EO-co-EEGE)-b-PEO obtained were removed by hydrolysis. The formed multi-arm star-shaped block copolymers of EO and glycidol (Gly) with multi-pendant hydroxymethyls (star-shaped block copolymer poly(EO-co-Gly)-b-PEO) were then esterified by the reaction of the pendant hydroxyl groups of glycidol units of copolymers with 2-bromoisobutyryl bromide, and the resulting star-shaped brush-like macroinitiators were used to initiate the grafting polymerization of t-butyl acrylate (tBA) by ATRP technique. Finally, the tert-butyl ester groups of PtBA grafting side chains were selectively hydrolyzed in trifluoroacetic acid ​(TFA) to obtain the water-soluble multi-arm star-shaped brush-like block copolymer (PEO-g-PAA)-b-PEO. The water-soluble star-shaped brush-like (PEO-g-PAA)-b-PEO, which consisted of a functional PAA domain as the core and a hydrophilic PEO domain as the shell, were exploited as polymeric nanoreactors to structure-direct in situ fabrication of CdSe quantum dots (QDs) colloidal nanocrystal clusters composed of primary CdSe nanocrystals as subunits, with the secondary structures of CdSe nanocrystals. Spherical CdSe colloidal nanocrystal clusters were intimately and permanently capped with hydrophilic PEO chains on the surface to render the resulting clusters with high water dispersible property.

A one-step in situ nanoconfined pyrolysis strategy was developed to anchor highly active single Co atoms on the P,N-doped porous carbon@carbon nanotube coaxial nanocables (Co-P,N-CNT), which exhibit remarkable enhanced ORR electrocatalytic activity in both acidic and alkaline media.

A series of optically active polyamides, PAnLATs (n = 9–12), were prepared by polycondensation of l-tartrate-derived diacid with achiral aliphatic diamines in which the number of the methylene is from 9 to 12. The monomers could be obtained easily, and the synthesis of the polyamides is facile. The number-average molecular weight (M̅n) of PA9LAT, PA10LAT, PA11LAT, and PA12LAT is 35 500, 24 400, 35 800, and 20 900 g/mol, respectively, and the related polydispersity index is 3.4, 3.3, 3.4, and 3.0. These polyamides display intense optical activity in solution. Particularly, the stronger ellipticities and different circular dichroism (CD) images were presented when the polymers were evaluated in the solid state. The crystalline properties of the polymers were studied to illuminate the enhanced aggregation-induced CD. Moreover, PA9LAT and PA11LAT have similar crystal parameters, and PA10LAT is similar to PA12LAT, which revealed why the chirality of the polyamides displays an odd–even effect. On the other hand, the solubility of the polymers in organic solvents was studied, and thermogravimetric-differential thermal analyzer was utilized to characterize the thermal properties.

Unimolecular core–shell and hollow polymer nanoparticles with well-defined dimensions were crafted using spherical core–shell star-like diblock copolymers as templates. Monodisperse and structurally stable star-like diblock copolymers composed of inner degradable core blocks and outer photo-cross-linkable shell blocks were synthesized via a combination of two living polymerization techniques, namely, coordination–insertion ring opening polymerization (ROP) followed by reversible addition–fragmentation chain-transfer polymerization (RAFT). Subsequently, uniform unimolecular core–shell nanoparticles were successfully produced by photo-cross-linking the shell blocks of star-like diblock copolymers. The core diameter and shell thickness of nanoparticles are determined by molecular weights of inner core block and outer shell block, respectively, thereby rendering nanoparticles with tunable structural characteristics. The cross-linking density of nanoparticles can be readily controlled by varying the exposure t...

A novel class of polymer, star-like poly(tert-butyl acrylate) (PtBA) capped with 4-isocyano-4′-(prop-2-yn-1-yloxy)biphenyl (CNBP), with a well-defined size was synthesized via atom transfer radical polymerization (ATRP) and click reaction (i.e., azide–alkyne cyclization). The star-like architecture was composed of 21 separate arms connected to a high-functionality β-cyclodextrin (β-CD) core. The inner star-like PtBA blocks were hydrolyzed into poly(acrylic acid) (PAA), yielding star-like CNBP-capped PAA (i.e., star-like PAA-CNBP). The starlike polymers were characterized by gel permeation chromatography (GPC) and dynamic light scattering (DLS) to confirm narrow size distribution, as well as being examined by proton nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectroscopy (FTIR), Raman, and atomic force microscopy (AFM) to verify successful attachment of the click-functionalized capping agent (i.e., CNBP) with structural similarity to low molar mass liquid crystal, 4-cyano-4′-pentylbiphenyl (5CB). Structure and phase behavior were evaluated by AFM and optical imaging. Star-like PAA-CNBP was found to possess improved solubility in a liquid crystal host and interesting surface structures.

A new class of star-shaped coil–rod diblock copolymer polystyrene-block-poly(3-hexylthiophene) (PS-b-P3HT) with well-defined structures and the ratio of coil to rod blocks were synthesized by a combination of atom transfer radical polymerization, the Grignard metathesis method, and click reaction. The star-shaped PS-b-P3HT diblock copolymers covalently connected to a β-cyclodextrin (β-CD) core were composed of 21-arm coil-like PS inner blocks and rod-like conjugated polymer P3HT outer blocks with narrow molecular weight distribution. The intermediate and final products were systematically characterized and confirmed by gel permeation chromatography (GPC), 1H nuclear magnetic resonance (1H-NMR), and Fourier transfer infrared (FTIR) spectroscopy. The optical properties of star-shaped PS-b-P3HT were examined by UV-Vis absorption and photoluminescence (PL) measurements. In comparison to the linear P3HT, due to their compact structure and the introduction of PS blocks, the optical properties of 21-arm, star-shaped PS-b-P3HT were altered. The star-shaped PS-b-P3HT formed unimolecular micelles in good solvent as revealed by dynamic light scattering (DLS) and atomic force microscopy (AFM) studies.

Cadmium telluride (CdTe) tetrapods were synthesized via multiple injections of the Te precursor by utilizing bifunctional ligands. Subsequently, tetrapod-shaped semiconducting inorganic-organic nanocomposites (i.e., P3HT-CdTe tetrapod nanocomposites) were produced by directly grafting conjugated polymer ethynyl-terminated poly(3-hexylthiophene) (i.e., P3HT-≡) onto azide-functionalized CdTe tetrapods (i.e., CdTe-N3) via a catalyst-free click chemistry. The intimate contact between P3HT and CdTe tetrapod rendered the effective dispersion of CdTe tetrapods in nanocomposites and facilitated their efficient electronic interaction. The success of coupling reaction was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The grafting density of P3HT chains on the CdTe tetrapods was estimated by thermogravimetric analysis. The photophysical properties of P3HT-CdTe tetrapod nanocomposites were studied using UV-vis and photoluminescence spectroscopies. These intimate semiconducting conjugated polymer-tetrapod nanocomposites may offer a maximized interface between conjugated polymers and tetrapods for efficient charge separation and enhanced charge transport regardless of their orientation for potential application in hybrid solar cells with improved power conversion efficiency.

The dielectric relaxation properties of poly(methylmethacrylate) (PMMA), polystyrene-block-poly(methylmethacrylate) (PS-b-PMMA) diblock copolymers and PS/PMMA blends were investigated by broadband dielectric spectroscopy in the frequency range from 0.01 Hz to 1 MHz and temperature range from − 40 to 150 °C. By parametric fitting techniques, an α relaxation process associated with the glass transition, the secondary β relaxation process due to localized motions of side groups, and the conductivity at low frequencies were identified and modeled for all samples. Based on the modeling results, the characteristic relaxation time, fragility index, activation energies, and relaxation strength of PMMA and PS-b-PMMA diblock copolymers were compared. It was found that the structural α relaxation of the copolymers was suppressed compared with that of PMMA. The covalent chemical bonds that link PS and PMMA blocks in the diblock copolymers are therefore assumed to dominate over the PMMA–PMMA, PMMA–PS and PS–PS bonds that exist in the PMMA and PS/PMMA samples, accounting for the suppression of the cooperative structural α relaxation and for larger activation energies of the localized β relaxation of the diblock copolymers. Further, the activation energy barriers of localized β relaxations in the copolymers are observed to increase, above the glass transition temperature.

Earning their stripes: A hierarchical assembly of micelles composed of an amphiphilic diblock copolymer, poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP), were made by combining controlled evaporative self-assembly of the confined PS-b-P4VP toluene solution in a cylinder-on-Si geometry with spontaneous self-assembly of micelles. This method gave microscopic stripes of nanometer-sized PS-b-P4VP micelles within the stripes (see pictures).

In situ precision synthesis of monodisperse hairy plasmonic nanoparticles with tailored dimensions and compositions by capitalizing on amphiphilic star-like diblock copolymers as nanoreactors are reported. Such hairy plasmonic nanoparticles comprise uniform noble metal nanoparticles intimately and perpetually capped by hydrophobic polymer chains (i.e., “hairs”) with even length. Interestingly, amphiphilic star-like diblock copolymer nanoreactors retain the spherical shape under reaction conditions, and the diameter of the resulting plasmonic nanoparticles and the thickness of polymer chains situated on the surface of the nanoparticle can be readily and precisely tailored. These hairy nanoparticles can be regarded as hard/soft core/shell nanoparticles. Notably, the polymer “hairs” are directly and permanently tethered to the noble metal nanoparticle surface, thereby preventing the aggregation of nanoparticles and rendering their dissolution in nonpolar solvents and the homogeneous distribution in polymer matrices with long-term stability. This amphiphilic star-like block copolymer nanoreactor-based strategy is viable and robust and conceptually enables the design and synthesis of a rich variety of hairy functional nanoparticles with new horizons for fundamental research on self-assembly and technological applications in plasmonics, catalysis, energy conversion and storage, bioimaging, and biosensors.

Extending the spectral absorption of organolead halide perovskite solar cells from visible into near-infrared (NIR) range renders the minimization of non-absorption loss of solar photons with improved energy alignment. Herein, we report on, for the first time, a viable strategy of capitalizing on judiciously synthesized monodisperse NaYF4 :Yb/Er upconversion nanoparticles (UCNPs) as the mesoporous electrode for CH3 NH3 PbI3 perovskite solar cells and more importantly confer perovskite solar cells to be operative under NIR light. Uniform NaYF4 :Yb/Er UCNPs are first crafted by employing rationally designed double hydrophilic star-like poly(acrylic acid)-block-poly(ethylene oxide) (PAA-b-PEO) diblock copolymer as nanoreactor, imparting the solubility of UCNPs and the tunability of film porosity during the manufacturing process. The subsequent incorporation of NaYF4 :Yb/Er UCNPs as the mesoporous electrode led to a high efficiency of 17.8 %, which was further increased to 18.1 % upon NIR irradiation. The in situ integration of upconversion materials as functional components of perovskite solar cells offers the expanded flexibility for engineering the device architecture and broadening the solar spectral use.

The ability to synthesize a diverse spectrum of one-dimensional (1D) nanocrystals presents an enticing prospect for exploring nanoscale size- and shape-dependent properties. Here we report a general strategy to craft a variety of plain nanorods, core-shell nanorods, and nanotubes with precisely controlled dimensions and compositions by capitalizing on functional bottlebrush-like block copolymers with well-defined structures and narrow molecular weight distributions as nanoreactors. These cylindrical unimolecular nanoreactors enable a high degree of control over the size, shape, architecture, surface chemistry, and properties of 1D nanocrystals. We demonstrate the synthesis of metallic, ferroelectric, upconversion, semiconducting, and thermoelectric 1D nanocrystals, among others, as well as combinations thereof.

A series of novel amphiphilic 21-arm, starlike diblock copolymers, poly(acrylic acid)-b-poly(3-hexylthiophene) (PAA-b-P3HT), based on β-cyclodextrin (β-CD) with well-defined molecular architectures and ratio of two chemically distinct blocks were prepared, for the first time, via a combination of quasi-living Grignard metathesis method (GRIM), click reaction, and atom transfer radical polymerization (ATRP). The starlike PAA-b-P3HT diblock copolymers consist of hydrophilic coil-like PAA cores and hydrophobic rodlike P3HT shells with narrow molecular weight distribution and well-defined molecular weight of each block. Owing to the compact structure, the amphiphilic starlike PAA-b-P3HT formed a unimolecular micelle. Emulsion based on these novel amphiphilic starlike, coil–rod diblock copolymers were readily produced by cross-linking hydrophilic coil-like PAA cores with a bifunctional cross-linker, ethylenediamine.

A series of novel amphiphilic multiarm, star-like block copolymers, poly(acrylic acid)-b-polystyrene (PAA-b-PS) based on β-cyclodextrin (β-CD) with well-defined molecular architectures, molecular weight, and ratio of two dissimilar blocks were prepared by sequential atom transfer radical polymerization (ATRP). β-CD with 21 hydroxyl groups was esterified by the reaction of its hydroxyl end groups with 2-bromoisobutyryl bromide, producing star-like heptakis[2,3,6-tri-O-(2-bromo-2-methylpropionyl]-β-cyclodextrin) (denoted 21-Br-β-CD). Subsequently, 21-Br-β-CD was utilized to initiate sequential ATRP of tert-butyl acrylate (tBA) and styrene (St). A series of 21-arm, star-like diblock copolymers, poly(tert-butyl acrylate)-b-polystyrene (PtBA-b-PS) were thus obtained. Finally, the ester groups of tBA in star-like PtBA-b-PS were selectively hydrolyzed by trifluoroacetic acid (TFA), thereby yielding amphiphilic 21-arm, star-like diblock copolymer PAA-b-PS with narrow molecular weight distribution (polydispersity ...

Conjugated polymers (CPs) have received considerable attention as promising materials for use in organic photovoltaics, light-emitting diodes (LEDs), thin film transistors, and biosensors. Among various types of CPs, poly(3hexylthiopene) (P3HT) is one of the most widely studied organic semiconductors. P3HT possesses excellent solution processability, environmental stability, high charge-carrier mobility, and tailorable electrochemical properties. Owing to their quantum-confined nature, for quantum dots (QDs) such as cadmium selenide (CdSe), variation of the nanocrystal size provides continuous and predictable changes in fluorescence emission, thus rendering them useful for a wide range of applications in photovoltaic cells, 7] LEDs, biosensors, and bio-imaging. CP-based organic/inorganic hybrid solar cells (e.g., CP/QD composites) are favorable alternatives to inorganic solar cells as they have many advantages peculiar to CPs, such as light weight, flexibility, processability, roll-to-roll production, low cost, and large area. However, the CP/QD composites are most often prepared by simply physically mixing the CPs and QDs. This procedure, however, suffers from several severe problems, including microscopic phase separation and the existence of insulating interfacial layers, thereby reducing the interfacial area between CPs and QDs and thus limiting the performance of the resulting devices. Recently, various methods have been utilized to overcome these problems, such as the use of cosolvent mixtures or binary solvent mixtures and surface modification of QDs. The most elegant approach is to chemically tether CPs on the QD surface (i.e., preparing CP–QD nanocomposites), hence enabling direct electronic coupling between CPs and QDs. Notably, this strategy has only recently been developed and has been primarily implemented by ligand exchange, which permits the derivatization of the composite with a broad range of functional groups. However, ligandexchange chemistry suffers from incomplete surface coverage. In this context, recently P3HT–CdSe-QD nanocomposites have been synthesized by directly grafting vinyl-terminated P3HT onto a [(4-bromophenyl)methyl]dioctylphosphine oxide(DOPO–Br)-functionalized CdSe QD surface by a mild palladium-catalyzed Heck coupling without the need for ligand exchange. The ability to manipulate the shape of nanocrystals has led to quantum rods (hereafter referred to as nanorods; NRs) with diameters that range from 2 to 10 nm and lengths ranging from 5 to 100 nm. Owing to their intrinsic structural anisotropy, NRs possess many unique properties that make them potentially better nanocrystals than QDs for photovoltaics and biomedical applications. Photovoltaic cells made of NRs and CPs show an improved optical absorption in the red and near-infrared ranges that originates from the NRs. Moreover, the long axis of the NRs provides continuous paths for the transport of electrons, an advantage over QDs, in which electron hopping between QDs is required. The performance of photovoltaic cells can be further improved if NRs are vertically aligned between two electrodes to minimize the carrier transport pathways. It is worth noting that although CP–NR nanocomposites were recently produced by ligand exchange of CPs with insulating ligands that were initially attached to the NR surface, direct grafting of CPs onto anisotropic nanocrystals has not yet been explored. Herein, we report one simple yet robust route to CP–NR nanocomposites that displaces the need for ligand-exchange chemistry. In this strategy, the catalyst-free alkyne–azide cycloaddition, which belongs to the emerging field of click chemistry, was utilized in the preparation of P3HT–CdSeNR nanocomposites. As shown in Scheme 1, CdSe NRs were passivated with bromobenzylphosphonic acid (BBPA), which not only induced elongated growth but also functionalized the CdSe NR surface and led to the formation of BBPA–CdSeNRs. Subsequently, the aryl bromide groups of BBPA were converted into azide groups, thus forming N3–BPA–CdSe NRs. Finally, catalyst-free Huisgen 1,3-dipolar cycloaddition between ethynyl-terminated P3HT and N3–BPA–CdSe NRs successfully gave P3HT–CdSe NR nanocomposites without the introduction of any deleterious metallic impurity. Click reactions possess several attractive features, including an extremely versatile bond-formation process, no need for protecting groups, good selectivity, nearly complete conversion, and generally no need for purification. As such, it stands out as a promising method to simplify the synthetic procedure and opens opportunities to increase the grafting density for large-scale synthesis. The charge transfer occurred at the P3HT/CdSe NR interface and was confirmed by [*] L. Zhao, Dr. X. Pang, Prof. Z. Lin Department of Materials Science and Engineering Iowa State University, Ames, IA 50011 (USA) and School of Materials Science and Engineering Georgia Institute of Technology, Atlanta GA 30332 (USA) Fax: (+1)515-294-7202 E-mail: zqlin@iastate.edu

A novel method for the synthesis of macrocyclic graft copolymers was developed through combination of anionic ring-opening polymerization (AROP) and atom transfer radical polymerization (ATRP). A linear α,ω-dihydroxyl poly(ethylene oxide) with pendant acetal protected hydroxyl groups (l-poly(EO-co-EEGE)) was prepared first by the anionic copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE). Then l-poly(EO-co-EEGE) was cyclized. The crude cyclized product containing the linear byproduct was hydrolyzed and purified by being treated with α-CD. The pure cyclic copolymer [c-poly(EO-co-Gly)] was esterified by reaction with 2-bromoisobutyryl bromide, and then used as ATRP macroinitiators to initiate polymerization of 2-(dimethylamino) ethyl methacrylate (DMAEMA), and a series of pH- and temperature-sensitive macrocyclic graft copolymers composed of a hydrophilic PEO as the ring and PDMAEMA as side chains (c-PEO-g-PDMAEMA) were obtained. The behavior of pH- and temperature-sensitive macrocyclic copolymers was studied in aqueous solution by fluorescence and dynamic light scattering (DLS). The critical micellization pH values of macrocyclic graft copolymers and their corresponding linear graft copolymers (l-PEO-g-PDMAEMA) were measured. Under the same conditions, the cyclic graft copolymer with the shorter side chains gave the higher critical micellization pH value. The c-PEO-g-PDMAEMA showed the lower critical micellization pH value than the corresponding l-PEO-g-PDMAEMA. The average hydrodynamic diameters (D h) of the micelles were measured by DLS with the variation of the aqueous solution pH value and temperature.

A series of amphiphilic macrocyclic graft copolymers composed of a hydrophilic poly(ethylene oxide) as ring and hydrophobic poly(ɛ-caprolactone) as lateral chains with different grafting lengths and densities of side chains were prepared by a combination of anionic ring-opening polymerization and coordination–insertion ring-opening polymerization. The anionic ring-opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using triethylene glycol and diphenylmethyl potassium (DPMK) as co-initiators, and a linear α,ω-dihydroxyl poly(ethylene oxide) with pendant protected hydroxymethyls ( l -poly(EO- co -EEGE)) was obtained. The monomer reactivity ratios of these compounds are r 1(EO) = 1.20 ± 0.01 and r 2(EEGE) = 0.76 ± 0.02, respectively. Then the ring closure of l -poly(EO- co -EEGE) was achieved via an ether linkage by reaction with tosyl chloride (TsCl) in the presence of solid KOH. The crude cyclized product containing the linear chain-extended polymer was hydrolyzed in acidic conditions first and then purified by treating with α-CD. The pure cyclic copolymer of EO and glycidol (Gly) with multipendant hydroxymethyls [ c -poly(EO- co -Gly)] as the macroinitiator was used further to initiate the ring-opening polymerization of ɛ-caprolactone (CL), and a series of amphiphilic macrocyclic graft copolymers c -PEO- g -PCL were obtained. The final products and intermediates were characterized by GPC, NMR and MALDI-TOF in detail.

A novel method for synthesis of amphiphilic macrocyclic graft copolymers with multi-polystyrene lateral chains is suggested, by combination of anionic ring-open polymerization (AROP) with atom transfer radical polymerization (ATRP). The anionic ring-opening copolymerization of ethylene oxide (EO) and ethoxyethyl glycidyl ether (EEGE) was carried out first using triethylene glycol and diphenylmethylpotassium. (DPMK) as coinitiators; the monomer reactivity ratio of them are r(1(EO)) = 1.20 +/- 40.01 and r(2(EEGE)) = 0.76 +/- 0.02 respectively. The obtained linear well-defined alpha,omega-dihydroxyl poly(ethylene oxide) with pendant protected hydroxylmethyls (l-poly(EO-co-EEGE)) was cyclized by reaction with tosyl chloride (TsCl) in the presence of solid KOH. The crude cyclized product containing the extended linear chain polymer was hydrolyzed and then purified by treat with alpha-CD. The pure cyclic copolymer with multipendant hydroxymethyls [c-poly(EO-co-Gly)] was esterified by reaction with 2-bromoisobutyryl bromide, and then used as macroinitiators to initiate polymerization of styrene (St), and a series of amphiphilic macrocyclic grafted copolymers composed of a hydrophilic PEO as ring and hydrophobic polystyrene as side chains (c-PEO-g-PS) were obtained. The intermediates and final products were characterized by GPC, NMR and MALDI-TOF in detail. The experimental results confirmed that c-PEO-g-PS shows stronger conjugation ability with the dyes than the corresponding comb-PEO-g-PS. (c) 2007 Wiley Periodicals, Inc.

in which the macromonomers are copolymerized.Itiswell-knownthatcontrolledpolymerizationssuchasanionic,ATRP, and RAFT are powerful tools for the synthesis of linearpolymerswithwell-controlledmolecularweightandpolydispersity,and it is possible to make topological tailoring on polymer by thereactionsofanionwithsomefunctionalcompoundsormodificationof the end groups.

Janus structures, named after the ancient two-faced Roman god Janus, comprise two hemistructures (e.g. hemispheres) with different compositions and functionalities. Much research has been carried out over the past few years on Janus structures because of the intriguing properties and promising potential applications of these unusually shaped materials. This Review discusses recent progress made in the synthesis, properties, and applications of strictly biphasic Janus structures possessing symmetrical structures but made of disparate materials. Depending on the chemical compositions, such biphasic structures can be categorized into soft, hard, and hybrid soft/hard Janus structures of different architectures, including spheres, rodlike, disclike, or any other shape. The main synthetic routes to soft, hard, and hybrid soft/hard Janus structures are summarized and their unique properties and applications are introduced. The perspectives for future research and development are also described.

Colloidal nanocrystals exhibit a wide range of size- and shape-dependent properties and have found application in myriad fields, incuding optics, electronics, mechanics, drug delivery and catalysis, to name but a few. Synthetic protocols that enable the simple and convenient production of colloidal nanocrystals with controlled size, shape and composition are therefore of key general importance. Current strategies include organic solution-phase synthesis, thermolysis of organometallic precursors, sol-gel processes, hydrothermal reactions and biomimetic and dendrimer templating. Often, however, these procedures require stringent experimental conditions, are difficult to generalize, or necessitate tedious multistep reactions and purification. Recently, linear amphiphilic block co-polymer micelles have been used as templates to synthesize functional nanocrystals, but the thermodynamic instability of these micelles limits the scope of this approach. Here, we report a general strategy for crafting a large variety of functional nanocrystals with precisely controlled dimensions, compositions and architectures by using star-like block co-polymers as nanoreactors. This new class of co-polymers forms unimolecular micelles that are structurally stable, therefore overcoming the intrinsic instability of linear block co-polymer micelles. Our approach enables the facile synthesis of organic solvent- and water-soluble nearly monodisperse nanocrystals with desired composition and architecture, including core-shell and hollow nanostructures. We demonstrate the generality of our approach by describing, as examples, the synthesis of various sizes and architectures of metallic, ferroelectric, magnetic, semiconductor and luminescent colloidal nanocrystals.

Polystyrene-capped barium titanate (BaTiO3) nanoparticles with sizes of 11 nm and 27 nm were prepared using amphiphilic star-like diblock copolymer templates. The crystal structure evolution of these nanoparticles over a wide temperature range (10–428 K) was investigated by powder X-ray diffraction. The Rietveld refinement indicates that the abrupt structural transitions observed in micron-sized powders become broad as the particle size is reduced to a few tens of nanometers. The orthorhombic phase (Amm2) is observed in the range of 10–388 K, coexisting with the rhombohedral phase (R3c) at lower temperatures and with the tetragonal phase (P4mm) at higher temperatures. At room temperature (300 K), polystyrene-capped BaTiO3 nanoparticles, both 11 and 27 nm sizes, primarily adopt the tetragonal phase, transforming to the cubic phase (Pmm) at 398 K during heating. The phase evolution of the nanoparticles correlates well with their dielectric behavior. With the Landauer–Bruggeman effective approximation, the dielectric properties at room temperature of the BaTiO3 core were calculated and the results are in agreement with the size effect of BaTiO3 nanocrystals.

Recent advances in the synthesis [ 1 ] and assembly [ 2 ] of nanocrystals (NCs) provide unique opportunities to exploit NCs for the development of next generation organic/inorganic hybrid solar cells as one of the most promising alternatives to Si solar cells to deliver effi cient energy conversion with inexpensive fabrication. [ 1 , 2 ] These conjugated polymer-based photovoltaic devices capitalize on the advantages peculiar to conjugated polymers (CPs), such as light weight, fl exibility, processability, roll-to-roll production, low cost, and large area, in conjunction with the high electron mobility and tunable optical properties of inorganic NCs. Of the organic/inorganic hybrids, poly(3-hexylthiopene) (P3HT) is one of the most extensively utilized CPs due to its excellent solution processability, environmental stability, high charge carrier mobility, and tailorable electrochemical properties. [ 3 , 4 ] CdSe quantum dots (QDs) are the most commonly investigated NCs because of their quantum-confi ned nature and well-matched energy level with P3HT. [ 5–11 ]