Thermally Reversible Aggregation of Gold Nanoparticles in Polymer Nanocomposites through Hydrogen Bonding

The ability to tune the state of dispersion or aggregation of nanoparticles within polymer-based nanocomposites, through variations in the chemical and physical interactions with the polymer matrix, is desirable for the design of materials with switchable properties. In this study, we introduce a simple and effective means of reversibly controlling the association state of nanoparticles based on the thermal sensitivity of hydrogen bonds between the nanoparticle ligands and the matrix. Strong hydrogen bonding interactions provide excellent dispersion of gold nanoparticles functionalized with poly­(styrene-<i>r</i>-2-vinylpyridine) [P­(S-<i>r</i>-2VP)] ligands in a poly­(styrene-<i>r</i>-4-vinyl phenol) [P­(S-<i>r</i>-4VPh)] matrix. However, annealing at higher temperatures diminishes the strength of these hydrogen bonds, driving the nanoparticles to aggregate. This behavior is largely reversible upon annealing at reduced temperature with redispersion occurring on a time-scale of ∼30 min for samples annealed 50 °C above the glass transition temperature of the matrix. Using ultraviolet–visible absorption spectroscopy (UV–vis) and transmission electron microscopy (TEM), we have established the reversibility of aggregation and redispersion through multiple cycles of heating and cooling

Structural Characteristics of Amphiphilic Cyclic and Linear Block Copolymer Micelles in Aqueous Solutions

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The effects of decomposition of CpZr(NMe2)3 on atomic layer deposition for high-k ZrO2 thin films

In this study, the thermal stability of cyclopentadienyl tris(dimethylamino)zirconium (CpZr(NMe2)3), a representative precursor for the deposition of ZrO2 films, was evaluated after exposure to thermal stress. As a result, we predicted that dimethylamine, and trimethylamine may be generated when CpZr(NMe2)3 was heated. These impurities affect the growth of film and the properties of the film. In particular, by changing the vapor pressure of CpZr(NMe2)3, thin films with different characteristics are formed under the same process conditions, and consequently, the reliability of the device was also reduced. Therefore, this study demonstrates that the decomposition of precursors must be studied to develop new precursors and highly reliable thin films and devices. © 2022 The AuthorsTRU

Abrupt Morphology Change upon Thermal Annealing in Poly(3-Hexylthiophene)/Soluble Fullerene Blend Films for Polymer Solar Cells

The in situ morphology change upon thermal annealing in bulk heterojunction blend films of regioregular poly(3-hexylthiophene) (P3HT) and 1-(3-metnoxycarbonyl)-propyl-1-phenyl-(6,6)C-61 (PCBM) is measured by a grazing incidence X-ray diffraction (GIXD) method using a synchrotron radiation source. The results show that the film morphology-including the size and population of P3HT crystallites-abruptly changes at 140 degrees C between 5 and 30 min and is then stable up to 120 min. This trend is almost in good agreement with the performance change of polymer solar cells fabricated under the same conditions. The certain morphology change after 5 min annealing at 140 degrees C is assigned to the on-going thermal transition of P3HT molecules in the presence of PCBM transition. Field-emission scanning electron microscopy measurements show that the crack-like surface of blend films becomes smaller after a very short annealing time, but does not change further with increasing annealing time. These findings indicate that the stability of P3HT:PCBM solar cells cannot be secured by short-time! annealing owing to the unsettled morphology, even though the resulting efficiency is high.X1189sciescopu

Structural Characteristics of Amphiphilic Cyclic and Linear Block Copolymer Micelles in Aqueous Solutions

The structural characteristics of aqueous micelles composed of amphiphilic cyclic poly(n-butyl acrylate-b-ethylene oxide) (cyclic PBA-b-PEO) or a linear analogue (i.e., linear poly(n-butyl acrylate-b-ethylene oxide-b-n-butyl acrylate) (linear PBA-b-PEO-b-PBA)) were examined for the first time using synchrotron X-ray scattering techniques and quantitative data analysis. The scattering data were analyzed using a variety of methodologies in a comprehensive complementary manner. These analyses provided details of the structural information about the micelles. Both micelles were found to consist of a core and a fuzzy shell; however, the cyclic block copolymer had a strong tendency to form micelles with core and shell parts that were more compact and dense than the corresponding parts of the linear block copolymer micelles. The PBA block of the cyclic copolymer was found to form a hydrophobic core with a density that exceeded the density of the homopolymer in the bulk state. The structural differences originated primarily from the topological difference between the cyclic and linear block copolymers. The elimination of the chain end groups (which introduced entropy and increased the excess excluded volume) from the amphiphilic block copolymer yielded more stable dense micelles in solution.X113125sciescopu

Polystyrene-b-polyisoprene thin films with hexagonally perforated layer structure: quantitative grazing-incidence X-ray scattering analysis

Grazing-incidence X-ray scattering (GIXS) formulas for hexagonally perforated layer (HPL) structures with ABC and AB stacking sequences were derived, and used in the quantitative analysis of the two-dimensional GIXS patterns of polystyrene-b-polyisoprene (PS-b-PI) diblock copolymer thin films supported on silicon substrates. This quantitative analysis provided detailed information ( shape, size and size distribution, packing order, layer packing sequence, and orientation) about the HPL structure of the diblock copolymer films that cannot be easily obtained with conventional X-ray and neutron scattering techniques or with conventional microscopic methods