To develop a feasible and efficient nanocarrier for potential clinical application, a series of photo and redox dual responsive reversibly cross-linked micelles have been developed for the targeted anticancer drug delivery. The nanocarrier can be cross-linked efficiently via a clean, efficient, and controllable coumarin photodimerization within the nanocarrier, which simplify the formulation process and quality control prior clinical use and improve the in vivo stability for tumor targeting. At the same time, cross-linking of nanocarrier could be cleaved via the responsiveness of the built-in disulfide cross-linkage to the redox tumor microenvironment for on-demand drug release. Coumarin and disulfide bond was introduced into a linear-dendritic copolymer (named as telodendrimer) precisely via peptide chemistry. The engineered nanocarrier possesses good drug loading capacity and stability, and exhibits a safer profile as well as similar anticancer effects compared with free drug in cell culture. The in vivo and ex vivo small animal imaging revealed the preferred tumor accumulation and the prolonged tumor residency of the payload delivered by the cross-linked micelles compared to the non-cross-linked micelles and free drug surrogate because of the increased stability.

A series of block and random copolymers consisting of oligo(ethylene glycol) and cholic acid pendant groups were synthesized via ring-opening metathesis polymerization of their norbornene derivatives. These block and random copolymers were designed to have similar molecular weights and comonomer ratios; both types of copolymers showed thermosensitivity in aqueous solutions with similar cloud points. The copolymers self-assembled into micelles in water as shown by dynamic light scattering and transmission electron microscopy. The hydrodynamic diameter of the micelles formed by the block copolymer is much larger and exhibited a broad and gradual shrinkage from 20 to 54 °C below its cloud point, while the micelles formed by the random copolymers are smaller in size but exhibited some swelling in the same temperature range. Based on in vitro drug release studies, 78% and 24% paclitaxel (PTX) were released in 24 h from micelles self-assembled by the block and random copolymers, respectively. PTX-loaded micelles formed by the block and random copolymers exhibited apparent antitumor efficacy toward the ovarian cancer cells with a particularly low half-maximal inhibitory concentration (IC50) of 27.4 and 40.2 ng/mL, respectively. Cholic acid-based micelles show promise as a versatile and potent platform for cancer chemotherapy.

Multishape memory copolymers were prepared through copolymerization of two norbornene derivatives: one based on cholic acid and the other on triethylene glycol monomethyl ether. The glass transition temperature (T g ) of the copolymers can be tuned over a temperature range from −58 to 176 °C. Most of these copolymers displayed a very broad T g over a 20 °C range which can allow a multishape memory effect. The shape memory properties of the copolymer incorporating an equal molar amount of both monomers have been studied in detail. The multishape memory effect was investigated by dynamic mechanical analysis using a thermomechanical programming process, in which multiple steps created two, three, and four temporary shapes. The polymer displayed good shape fixing and recovery in different thermal processing stages over the broad glass transition range. This series of copolymers with broad and tunable T g 's may be useful as functional materials with multishape memory effect.

Electrodeposition of lithium-ion battery cathodes enables ultraflexible, ultrathick, and high-power rechargeable batteries.

Ferroelectric materials exhibit the largest dielectric permittivities and piezoelectric responses in nature, making them invaluable in applications from supercapacitors or sensors to actuators or electromechanical transducers. The origin of this behavior is their proximity to phase transitions. However, the largest possible responses are most often not utilized due to the impracticality of using temperature as a control parameter and to operate at phase transitions. This has motivated the design of solid solutions with morphotropic phase boundaries between different polar phases that are tuned by composition and that are weakly dependent on temperature. Thus far, the best piezoelectrics have been achieved in materials with intermediate (bridging or adaptive) phases. But so far, complex chemistry or an intricate microstructure has been required to achieve temperature-independent phase-transition boundaries. Here, we report such a temperature-independent bridging state in thin films of chemically simple BaTiO 3 . A coexistence among tetragonal, orthorhombic, and their bridging low-symmetry phases are shown to induce continuous vertical polarization rotation, which recreates a smear in-transition state and leads to a giant temperature-independent dielectric response. The current material contains a ferroelectric state that is distinct from those at morphotropic phase boundaries and cannot be considered as ferroelectric crystals. We believe that other materials can be engineered in a similar way to contain a ferroelectric state with gradual change of structure, forming a class of transitional ferroelectrics. Similar mechanisms could be utilized in other materials to design low-power ferroelectrics, piezoelectrics, dielectrics, or shape-memory alloys, as well as efficient electro-and magnetocalorics.

Intermetallics are compounds with long-range structural order that often lies in a state of thermodynamic minimum. They are usually considered as favorable structures for catalysis due to their high activity and robust stability. However, formation of intermetallic compounds is often regarded as element specific. For instance, Ag and Pt do not form alloy in bulk phase through the conventional metallurgy approach in almost the entire range of composition. Herein, we demonstrate a bottom-up approach to create a new Ag-Pt compositional intermetallic phase from nanoparticles. By thermally treating the corresponding alloy nanoparticles in inert atmosphere, we obtained an intermetallic material that has an exceptionally narrow Ag/Pt ratio around 52/48 to 53/47, and a structure of interchangeable closely packed Ag and Pt layers with 85% on tetrahedral and 15% on octahedral sites. This rather unique stacking results in wavy patterns of Ag and Pt planes revealed by scanning transmission electron microscope (STEM). This Ag-Pt compositional intermetallic phase is highly active for electrochemical oxidation of formic acid at low anodic potentials, 5 times higher than its alloy nanoparticles, and 29 times higher than the reference Pt/C at 0.4 V (vs RHE) in current density.

A new aromatic, unsymmetrical ether diamine with a trifluoromethyl pendent group, 1,4‐(2′‐trifluoromethyl‐4′,4″‐diaminodiphenoxy)benzene, was successfully synthesized in three steps with hydroquinone as a starting material and polymerized with various aromatic tetracarboxylic acid dianhydrides, including 4,4′‐oxydiphthalic anhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, 2,2′‐bis(3,4‐dicarboxyphenyl)‐hexafluoropropane dianhydride, and pyromellitic dianhydride, via a conventional two‐step thermal or chemical imidization method to produce a series of fluorinated polyimides. The polyimides were characterized with solubility tests, viscosity measurements, IR, 1H NMR, and 13C NMR spectroscopy, X‐ray diffraction studies, and thermogravimetric analysis. The polyimides had inherent viscosities of 0.56–0.77 dL/g and were easily dissolved in both polar, aprotic solvents and common, low‐boiling‐point solvents. The resulting strong and flexible polyimide films exhibited excellent thermal stability, with decomposition temperatures (at 5% weight loss) above 522 °C and glass‐transition temperatures in the range of 232–272 °C. Moreover, the polymer films showed outstanding mechanical properties, with tensile strengths of 74.5–121.7 MPa, elongations at break of 6–13%, and initial moduli of 1.46–1.95 GPa, and good dielectric properties, with low dielectric constants of 1.82–2.53 at 10 MHz. Wide‐angle X‐ray diffraction measurements revealed that these polyimides were predominantly amorphous. These outstanding combined features ensure that the polymers are desirable candidate materials for advanced microelectronic applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6836–6846, 2006

H 2 O 2 production by direct synthesis (H 2 + O 2 → H 2 O 2 ) is a promising alternative to the energy-intensive anthraquinone oxidation process and to the use of chlorine for oxidation chemistry. Steady-state H 2 O 2 selectivities are approximately 10-fold greater on AgPt octahedra (50%) than on Pt nanoparticles of similar size (6%). Moreover, the initial H 2 O 2 formation rates and selectivities are sensitive to the fractional coverage of Pt atoms and their location on the surfaces of AgPt octahedra, which can be controlled by exposing these catalysts to either CO or inert gases at 373 K to produce Pt-rich (16% initial H 2 O 2 selectivity) or Pt-poor (36% initial H 2 O 2 selectivity) surfaces. Increasing the coordination of Pt to Ag significantly modifies the electronic structure of Pt active sites, which is reflected by a shift in the ν(C=O) singleton frequency in 13 CO from 2016 cm −1 on Pt to ∼1975 cm −1 on AgPt. These bimetallic AgPt catalysts present lower activation enthalpies (ΔH ⧧ ) for H 2 O 2 formation (29 kJ mol −1 on Pt to 5 kJ mol −1 on AgPt) but a lesser decrease for H 2 O formation (26 kJ mol −1 on Pt to 16 kJ mol −1 on AgPt). Comparisons of H 2 O 2 selectivities, ΔH ⧧ values, and differences among the 13 CO singleton frequencies show that a combination of coordinating Ag to Pt and inducing strain modifies the electronic structure of individual Pt atoms, causing them to bind η 1species (e.g., CO) more strongly than on Pt nanoparticles. Yet the dramatic increase in the number of isolated Pt atoms increases H 2 O 2 selectivities by decreasing the number of Pt atom ensembles of sufficient size to cleave O−O bonds and form H 2 O.