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Despite a huge variety of methodologies having been proposed to produce photonic structures by self-assembly, the lack of an effective fabrication approach has hindered their practical uses. These approaches are typically limited by the poor control in both optical and mechanical properties. Here we report photonic thermosetting polymeric resins obtained through brush block copolymer (BBCP) self-assembly. We demonstrate that the control of the interplay between order and disorder in the obtained photonic structure offers a powerful tool box for designing the optical appearance of the polymer resins in terms of reflected wavelength and scattering properties. The obtained materials exhibit excellent mechanical properties with hardness up to 172 MPa and Young's modulus over 2.9 GPa, indicating great potential for practical uses as photonic coatings on a variety of surfaces. [ABSTRACT FROM AUTHOR]

Fabrication of films with plasmonic nanoparticles (NPs) arrays arranged in chiral configurations of prescribed handedness is highly attractive for the design of new functional materials; however, this remains a formidable challenge in nanotechnology. In this study, we demonstrated the controlled arrangements of gold (Au) NPs into helical structures templated by helical pores created in cross-linked block copolymer (BCP) films. d- and l-tartaric acid (TA) were used to direct the self-assembly of achiral poly(1,4-butadiene)-b-poly(ethylene oxide) BCPs into helical cylindrical morphologies with prescribed handedness, i.e., D or L. Helical pores were generated by BCP cross-linking followed by TA extraction. Helical Au NP arrays, subsequently arranged within the helical pores, exhibited the chiral optical response. The helical structures of NPs arrays and the resulting optical handedness were tunable simply by using either D- or L-porous templates. This simple strategy offers a straightforward pathway for the fabrication of chiral porous BCP films and helical NPs arrays with chiral optical properties. [ABSTRACT FROM AUTHOR]

A systematic study was conducted to investigate the morphology transitions that occur in polystyrene-block-poly(ethylene oxide) (PS-b-PEO) bottlebrush block copolymers (BBCP) upon varying PEO volume fraction (fPEO) from 22% to 81%. A series of PS-b-PEO BBCPs with different PEO side chain lengths were prepared using ring-opening metathesis polymerization (ROMP) of PEO-norbornene (PEO-NB) (Mn ∼ 0.75, 2.0, or 5.0 kg/mol) and PS-norbornene (PS-NB) (Mn ∼ 3.5 kg/mol) macromonomers (MM). A map of fPEO versus side chain asymmetry (Mn(PEO-NB)/Mn(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 fPEO from 28% to 72%. At high fPEO, 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 TMST 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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(tert-butyl acrylate)-block-poly(ethylene oxide) (PtBA-b-PEO) BBCPs with a fixed side chain length of PtBA (Mn = 8.2 kg/mol) but with different PEO brush lengths (Mn = 5.0, 2.0, or 0.75 kg/mol) as well as volume fractions (fPEO = 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 (fNP/PEO) of NPs and PEO domain. Symmetric or asymmetric lamellar morphologies of NP arrays were readily created through simple variation of fNP/PEO. Interestingly, a lamellar structure was obtained at a small fNP/PEO of only 0.248 for nanocomposites based on BBCPs with comparable side chain lengths (MWPEO/MWPtBA = 0.63). In contrast, NP morphological transitions from wormlike through cylindrical to lamellar structures were observed with the increase of fNP/PEO for nanocomposites based on BBCPs with a large difference in side chain length (MWPEO/MWPtBA = 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. [ABSTRACT FROM AUTHOR]

We report the directed assembly of quantum dots (QDs) within well-ordered photonic nanocomposites using a family of (polynorbornene-graft-poly(styrene))-block-(polynorbornene-graft-poly(ethylene oxide)) (PS-b-PEO) brush block copolymers (BBCPs). Cadmium selenide (CdSe) nanoparticles (NPs) modified with 11-mercaptoundecylhydroquinone are selectively incorporated within the PEO domains of the self-assembled BBCPs via strong hydrogen-bonding interactions between the ligands on QDs and PEO brushes of the BBCPs. Well-ordered QD arrays were readily created within a periodic lamellar polymer matrix, or one-dimensional photonic crystal, with a widely tunable lattice spacing ranging from 46.2 to up to 145 nm. The loading concentration of the QDs can be up to 30 wt % (15 vol %) while maintaining a well-ordered lamellar morphology, providing an optical gain material platform for the systematic investigation of optical properties. Strong photoluminescence and third harmonic generation from the well-ordered QD arrays were observed via multiphoton excitation using femtosecond (fs) laser light at several optical wavelengths from 700 to 1550 nm. [ABSTRACT FROM AUTHOR]

We report that an exceptionally large volume of highly ordered arrays (single grains) on the order of millimeters in scale can be rapidly created through a unique innate guiding mechanism of brush block copolymers (BBCPs). The grain volume is over 109 times larger than that of typical self-assembled linear BCPs (LBCPs). The use of strong interactions between nanoparticles (NPs) and BBCPs enables high loadings of functional materials, up to 76 wt % (46 vol %) in the target domain, while maintaining excellent long-range order. Overall, this work provides a simple method to precisely control the spatial orientation of functionalities at nanometer length scales over macroscopic volumes, thereby enabling the production of hybrid materials for many important applications. [ABSTRACT FROM AUTHOR]

To date the self-assembly of ordered metal nanoparticle (NP)/block copolymer hybrid materials has been limited to NPs with core diameters (Dcore) 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 (Dcore = 15.8 ± 1.3 nm) bearing poly(4-vinylphenol) ligands were selectively incorporated within the hydrophilic domains of a phase-separated (polynorbornene-g-polystyrene)-fo-(pol- ynorbornene-g-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. [ABSTRACT FROM AUTHOR]

A series of novel neutral nickel complexes based on cyclic β-ketiminato ligands, [(2,6-iPr2C6H3)NCHC6H8O]Ni(Ph)(PPh3) (3b), [(2,6-iPr2C6H3)NCHCn+3H2n+2O(C6H4)]Ni(Ph)(PPh3) (6a−c), and [(2,6-iPr2C6H3)NCHCn+3H2n+2O(C6H4)]Ni(CH3)(Py) (7a−c: a, n= 0; b, n= 1; c, n= 2) have been synthesized and characterized. These conveniently accessible complexes proved to be highly active catalysts for ethylene polymerization without an activator. Under the optimized conditions, an activity of 71.4 kg of PE/((mol of Ni) h atm) was observed using 6cas a catalyst. Particularly, it is of great interest that a bulky substituent proximate to the oxygen atom of the β-ketiminato complex is no longer a prerequisite to attain high catalytic efficiency, which is much different from the case for salicylaldiminato neutral nickel catalysts. This is effectively supported by the lower activation enthalpy changes of complexes 3band 6a−crelative to values for the classic salicylaldiminato complexes. Moreover, for complexes 6a−cand 7a−c, the degree of conjugation between the phenylene ring and the corresponding nickel chelate of the complex can be tuned via changes in the ligand structure, which remarkably influence the molecular weights and the microstructures of the resulting polyethylenes. In comparison with the highly conjugated complexes 6aand 7a, complexes 6b,cand 7b,c, with a low degree of conjugation, produced polyethylenes with much higher molecular weights and lower branch contents. X-ray crystallographic analysis of 3band 6a−cprovides detailed information about the differences among these structures, and various typical angles and bond distances produce evidence of the conjugation modulation effect. [ABSTRACT FROM AUTHOR]

A series of novel neutral nickel complexes 4a−ebearing modified β-ketoiminato ligands [(2,6-iPr2C6H3)NC(R1)CHC(2′-R2C6H4)O]Ni(Ph)(PPh3) (4a, R1= R2= H; 4b, R1= H, R2= Ph; 4c, R1= H, R2= Naphth; 4d, R1= CH3, R2= Ph; 4e, R1= CF3, R2= Ph) have been synthesized and characterized. Molecular structures of 4band 4ewere further confirmed by X-ray crystallographic analysis. Activated with B(C6F5)3, all the complexes are active for the polymerization of ethylene to branched polyethylenes. Ligand structure, i.e., substituents R1and R2, greatly influences not only catalytic activity but also the molecular weight and branch content of the polyethylene produced. The phenyl-substituted complex 4bexhibits the highest activity of up to 145 kg PE/molNi·h·atm under optimized conditions, which is about 10 times more than unsubstituted complex 4a(14.0 kg PE/molNi·h·atm). Highly branched polyethylene with 103 branches per 1000 carbon atoms has been prepared using catalyst 4e. [ABSTRACT FROM AUTHOR]