Synthesis and Controlled Self-Assembly of UV-Responsive Gold Nanoparticles in Block Copolymer Templates

We demonstrate the facile synthesis of gold nanoparticles (GNPs) functionalized by UV-responsive block copolymer ligands, poly­(styrene)-<i>b</i>-poly­(<i>o</i>-nitrobenzene acrylate)-SH (PS-<i>b</i>-PNBA-SH), followed by their targeted distribution within a lamellae-forming poly­(styrene)-<i>b</i>-poly­(2-vinylpyridine) (PS-<i>b</i>-P2VP) block copolymer. The multilayer, micelle-like structure of the GNPs consists of a gold core, an inner PNBA layer, and an outer PS layer. The UV-sensitive PNBA segment can be deprotected into a layer containing poly­(acrylic acid) (PAA) when exposed to UV light at 365 nm, which enables the simple and precise tuning of GNP surface properties from hydrophobic to amphiphilic. The GNPs bearing ligands of different chemical compositions were successfully and selectively incorporated into the PS-<i>b</i>-P2VP block copolymer, and UV light showed a profound influence on the spatial distributions of GNPs. Prior to UV exposure, GNPs partition along the interfaces of PS and P2VP domains, while the UV-treated GNPs are incorporated into P2VP domains as a result of hydrogen bond interactions between PAA on the gold surface and P2VP domains. This provides an easy way of controlling the arrangement of nanoparticles in polymer matrices by tailoring the nanoparticle surface using UV light

Polystyrene-<i>block</i>-poly(ethylene oxide) Bottlebrush Block Copolymer Morphology Transitions: Influence of Side Chain Length and Volume Fraction

A systematic study was conducted to investigate the morphology transitions that occur in polystyrene-<i>block</i>-poly­(ethylene oxide) (PS-<i>b</i>-PEO) bottlebrush block copolymers (BBCP) upon varying PEO volume fraction (<i>f</i>_PEO) from 22% to 81%. A series of PS-<i>b</i>-PEO BBCPs with different PEO side chain lengths were prepared using ring-opening metathesis polymerization (ROMP) of PEO–norbornene (PEO-NB) (<i>M</i>_n ∼ 0.75, 2.0, or 5.0 kg/mol) and PS–norbornene (PS-NB) (<i>M</i>_n ∼ 3.5 kg/mol) macromonomers (MM). A map of <i>f</i>_PEO versus side chain asymmetry (<i>M</i>_n(PEO-NB)/<i>M</i>_n(PS-NB)) was constructed to describe the BBCP phase behavior. Symmetric and asymmetric lamellar morphologies were observed in the BBCPs over an exceptionally wide range of <i>f</i>_PEO from 28% to 72%. At high <i>f</i>_PEO, crystallization of PEO was evident. Temperature-controlled SAXS and WAXS revealed the presence of high order reflections arising from phase segregation above the PEO melting point. A microphase transition temperature <i>T</i>_MST was observed over a temperature range of 150–180 °C. This temperature was relatively insensitive to both side chain length and volume fraction variations. The findings in this study provide insight into the rich phase behavior of this relatively new class of macromolecules and may lay the groundwork for their use as templates directing the fabrication of functional materials

Rapid, Large-Area Synthesis of Hierarchical Nanoporous Silica Hybrid Films on Flexible Substrates

We report a simple strategy for the creation of large-area nano­porous hybrid films of silica, carbon, and gold on poly­ethylene tere­phthalate via photo­thermal processing. This method enables the selective heating of light-absorbing thin films on low-temperature substrates using sub-milli­second light pulses generated by a xenon flash lamp. The film contains gold nano­particles as the nano­heaters to convert light energy to heat, a sacrificial block copolymer surfactant to generate mesopores, and cross-linked poly­hedral oligo­meric silsesqui­oxane as the silica source to form the skeleton of the porous structure. Hier­archical porous structures are achieved in the films after photo­thermal treatment, with uniform meso­pores (44–48 nm) on the surface and inter­connected macro­pores (>50 nm) under­neath resulting from a foaming effect during release of gaseous decomposition products. The loading of gold nano­particles is up to 43 wt % in the product, with less than 2 wt % organic residue. This rapid and large-area process for the synthetis of porous structures is compatible with roll-to-roll manufacturing for the fabrication of flexible devices

Structural Diversity and Phase Behavior of Brush Block Copolymer Nanocomposites

Brush block copolymers (BBCPs) exhibit attractive features for use as templates for functional hybrid nanomaterials including rapid ordering dynamics and access to broad ranges of domain sizes; however, there are relatively few studies of the morphology of the BBCPs as a function of their structural variables and fewer still studies of BBCP composite systems. Here we report the structural diversity and phase behavior of one class of BBCP nanocomposites as a function of the volume fractions of their components and the side chain symmetry of the BBCPs. We conducted a systematic investigation of gold nanoparticle (NP) (∼2 nm) assembly in a series of poly­(<i>tert</i>-butyl acrylate)-<i>block</i>-poly­(ethylene oxide) (P<i>t</i>BA-<i>b</i>-PEO) BBCPs with a fixed side chain length of P<i>t</i>BA (<i>M</i>_n = 8.2 kg/mol) but with different PEO brush lengths (<i>M</i>_n = 5.0, 2.0, or 0.75 kg/mol) as well as volume fractions (<i>f</i>_PEO = 0.200–0.484). The gold NPs are selectively incorporated within the PEO domain via hydrogen bond interactions between the 4-mercaptophenol ligands of the gold NPs and the PEO side chains. A number of morphological transitions were observed and were dependent on the total volume fraction (<i>f</i>_NP/PEO) of NPs and PEO domain. Symmetric or asymmetric lamellar morphologies of NP arrays were readily created through simple variation of <i>f</i>_NP/PEO. Interestingly, a lamellar structure was obtained at a small <i>f</i>_NP/PEO of only 0.248 for nanocomposites based on BBCPs with comparable side chain lengths (MW_PEO/MW_PtBA = 0.63). In contrast, NP morphological transitions from wormlike through cylindrical to lamellar structures were observed with the increase of <i>f</i>_NP/PEO for nanocomposites based on BBCPs with a large difference in side chain length (MW_PEO/MW_PtBA = 0.09). Highly deformed cylinders were observed in the cylindrical morphology as clearly identified by high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) tomography. This work represents a starting point for understanding BBCP composite phase behavior, and it provides new insight toward strategies for control over the microstructure of NP arrays assembled in BBCP templates, which is essential for functional materials design

Ligand Steric and Electronic Effects on β-Ketiminato Neutral Nickel(II) Olefin Polymerization Catalysts

A series of novel neutral nickel complexes <b>3a</b>–<b>g</b> and <b>4a</b>–<b>d</b> bearing the β-ketiminato ligands [(2,6-ⁱPr₂C₆H₃)­NCHCHC­(R)­O]­Ni­(R′)­(L) (for <b>3a</b>–<b>g</b>, R′ = Me, L = Py, and R = ^tBu (<b>3a</b>), Ph (<b>3b</b>), 1-naphthyl (<b>3c</b>), 9-anthryl (<b>3d</b>), PhNMe₂(<i>p</i>) (<b>3e</b>), PhOMe­(<i>p</i>) (<b>3f</b>), PhCF₃(<i>p</i>) (<b>3g</b>); for <b>4a</b>–<b>d</b>, R′ = Ph, L = PPh₃, and ^tBu (<b>4a</b>), Ph (<b>4b</b>), 1-naphthyl (<b>4c</b>), 9-anthryl (<b>4d</b>)) have been synthesized and characterized. The molecular structures of <b>3b</b>–<b>d</b>,<b>f</b>,<b>g</b> and <b>4a</b>,<b>c</b> were further confirmed by X-ray crystallographic analysis. These complexes were employed in ethylene polymerization to systematically investigate ligand steric and electronic effects on the catalytic properties, including activity, molecular weight (MW), and branching number of the polyethylene obtained. The complexes bearing more bulky ligands showed higher activities and produced more branched polyethylene. Electron-deficient ligands were found to increase the catalytic activity, decrease the MW, and enhance the branching content of the polyethylene. In addition, phosphine Ni^II–Ph complexes <b>4a</b>–<b>d</b> proved to be more active than the corresponding pyridine Ni^II–Me complexes <b>3a</b>–<b>d</b>, probably due to the easier dissociation of PPh₃ relative to a pyridine from a nickel center

Controlled Supramolecular Self-Assembly of Large Nanoparticles in Amphiphilic Brush Block Copolymers

To date the self-assembly of ordered metal nanoparticle (NP)/block copolymer hybrid materials has been limited to NPs with core diameters (<i>D</i>_core) of less than 10 nm, which represents only a very small fraction of NPs with attractive size-dependent physical properties. Here this limitation has been circumvented using amphiphilic brush block copolymers as templates for the self-assembly of ordered, periodic hybrid materials containing large NPs beyond 10 nm. Gold NPs (<i>D</i>_core = 15.8 ± 1.3 nm) bearing poly­(4-vinylphenol) ligands were selectively incorporated within the hydrophilic domains of a phase-separated (polynorbornene-<i>g</i>-polystyrene)-<i>b</i>-(polynorbornene-<i>g</i>-poly­(ethylene oxide)) copolymer via hydrogen bonding between the phenol groups on gold and the PEO side chains of the brush block copolymer. Well-ordered NP arrays with an inverse cylindrical morphology were readily generated through an NP-driven order–order transition of the brush block copolymer

THE DEVELOPMENT OF THE TECHNOLOGICAL BASES FOR OBTAINING AND PROCESSING OF THE BASE THERMOPLASTIC BUTADIEN-NITRIL ELASTOMERS

The object of investigation: the butadien-nitril rubber, polyvinylchloride, polystirol, polycarbonate, ABC-plastics, polyamide, acetylcellulose, polypropylene. The theoretical justification has been given, the mathematical model of the quality of the base materials, the mathematical model of optimization of the modified thermoplastic elastomers recipe have been developed, the influence of the fillers and plastificators of the different nature on the consumers properties of the base materials has been developed, the method of prognosing of the materials technological properties has been developed. Offered has been the method of the &quot;dynamic&quot; vulcanization, with the aid of which the base materials have been received, and it allows to reduce the time of the vulcanization by 5 times and to reduce the electric power consumption. The recipes of the cast compositions, posessing the improved values of the operating and consumer properties, the modes and the parameters of the processing of the base materials, the multiple use of the obtained alloys have been offered. The base polymer materials of the new type for casting under pressure have been introduced in practiceAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio