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Shape- and structure-controlled block copolymer particles have received great attention due to their unusual physical properties, hence achieving structural diversity of the particles is highly des...

Hybrid organic/inorganic systems with modulated nanostructures and well-defined morphologies are of great importance to develop novel nanomaterials with tailored functionalities. Herein, we report ...

Interface engineering of evaporative emulsion droplets containing block copolymers (BCPs) provides an effective route to generate nonspherical particles. Here, we demonstrate the impact of length-controlled nanorods (NRs) on the interfacial properties of BCP emulsions to produce anisotropic BCP particles. A series of lamellae- and cylinder-forming polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and a series of NRs with different lengths (l) are coassembled, and selective arrangement of the NRs on the P4VP domain at the particle surface enables the production of striped football (prolate) and convex lens-shaped (oblate) particles. In particular, the ratio of the NR length to the size of the NR-hosting domain (l/L), which is varied from 0.07 to 3.60, is the key parameter in determining the location of the NRs in the BCP particles as well as the final particle shape. The oblate particles are generated only in the range of 0.36 ≤ l/L ≤ 0.96, whereas the prolate particles are produced for much wider range of l...

A powerful strategy to enhance the thermal conductivity of liquid crystalline epoxy resin (LCER) by simply replacing the conventional amine cross-linker with a cationic initiator was developed. The cationic initiator linearly wove the epoxy groups tethered on the microscopically aligned liquid crystal mesogens, resulting in freezing of the ordered LC microstructures even after curing. Owing to the reduced phonon scattering during heat transport through the ordered LC structure, a dramatic improvement in the thermal conductivity of neat cation-cured LCER was achieved to give a value ∼141% (i.e., 0.48 W/mK) higher than that of the amorphous amine-cured LCER. In addition, at the same composite volume fraction in the presence of a 2-D boron nitride filler, an approximately 130% higher thermal conductivity (maximum ∼23 W/mK at 60 vol %) was observed. The nanoarchitecture effect of the ordered LCER on the thermal conductivity was then examined by a systematic investigation using differential scanning calorimetry, polarized optical microscopy, X-ray diffraction, and thermal conductivity measurements. The linear polymerization of LCER can therefore be considered a practical strategy to enable the cost-efficient mass production of heat-dissipating materials, due to its high efficiency and simple process without the requirement for complex equipment.

We report a simple and robust strategy to prepare pH-responsive biphasic Janus particles composed of polystyrene/poly(2-vinylpyridine) (PS/P2VP) homopolymers that are able to control the reversible formation, breakage, and switching of Pickering emulsions depending on their geometry- and pH-dependent hydrophilic–lipophilic balance. The chemical stability of these PS/P2VP Janus particles was tuned through the incorporation of cross-linkable benzophenone units along the backbone of the homopolymers. By employing these stabilized particles as emulsifiers for toluene and water, a facile transformation of emulsion types (i.e., from toluene-in-water to water-in-toluene emulsions) was achieved by adjusting the pH of the aqueous phase. More importantly, this pH-dependent switching behavior and associated stability of the emulsions could be actively controlled by adjusting the relative size ratio of PS to P2VP. When the PS volume fraction (ϕPS) was between 0.33 and 0.67, a wide range tuning of emulsion phase inclu...

Surface-engineered, 10 nm-sized graphene quantum dots (GQDs) are shown to be efficient surfactants for producing 3-pentadecyl phenol (PDP)-combined poly(styrene-b-4-vinylpyridine) (PS-b-P4VP(PDP)) particles that feature tunable shapes and internal morphologies. The surface properties of GQDs were modified by grafting different alkyl ligands, such as hexylamine and oleylamine, to generate the surfactant behavior of the GQDs. In stark contrast to the behavior of the unmodified GQDs, hexylamine-grafted GQDs and oleylamine-grafted GQD surfactants were selectively positioned on the PS and P4VP(PDP) domains, respectively, at the surface of the particles. This positioning effectively tuned the interfacial interaction between two different PS/P4VP(PDP) domains of the particles and the surrounding water during emulsification and induced a dramatic morphological transition to convex lens-shaped particles. Precise and systematic control of interfacial activity of GQD surfactants was also demonstrated by varying the ...

Combining the functionality of nanoparticles (NPs) with the processability of polymers offers great promise for designing novel materials. In particular, NPs with tailored surface properties can effectively modify the interface between two distinct fluids and/or different polymer matrices which allows them to function as efficient surfactants. The efficiency of NP surfactants is strongly affected by their size and shape, which influences their adsorption energy to the interface, and the entropic contribution to the system. In this review, the assembly of size- and shape-controlled inorganic NPs at the interface of block copolymers (BCPs) and polymer blends has been focused. First, we discuss the design of size- and shape-controlled NP surfactants and we review the examples of NP surfactant-driven BCPs and polymer blend morphologies. In addition, we review the recent investigations of the morphological transition of BCP emulsion particles induced by NP surfactants. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 228–237

Block copolymer/nanoparticle (BCP/NP) composites have attracted much attention due to their easiness of fabricating nanoscopic hierarchical structures, and significantly enhanced chemical and physical properties of the nanocomposites. Most of the focus in co-assembly of BCPs and NPs has been placed on the controlled alignment of NPs, “passively,” in the BCP domain. However, NPs with carefully designed interfacial properties “actively” direct self-assembled structure of BCP in a nonconventional route. Herein, we review recent investigations of the self-assembly of BCP domains in thin films via the addition of structure-directing organic and inorganic NPs. Understanding the phase behavior of BCP/NP co-assembly along with the theoretical description can shed a light on the far-reaching potentials to creating nonconventional nanostructures rarely obtained via traditional fabrication tools. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015

Monodisperse colloidal particles of polystyrene-b-polybutadiene (PS-b-PB) block copolymers (BCPs) were successfully prepared, in which uniform emulsions containing BCPs were first generated by cross-flow membrane emulsification using tubular Shirasu porous glass (SPG) membrane, and then unique internal nanostructures were developed by controlled evaporation of solvent inside emulsion. The diameter of those BCP particles could be controlled from 200 nm to 5 μm by tuning the pore diameter of the membrane. With symmetric BCPs, onion-like nanostructures inside particles were formed. Coiled cylinders in the BCP particles were also developed by adding homopolymers, in which the assembled BCP structure is strongly dependent on the particle size, demonstrating the importance of our membrane method in generating monodisperse BCP particles. Further investigation of process parameters showed that for a given pore diameter, the operation pressure (P) and surfactant concentration were critical parameters for narrow si...

Shape, size, and orientation of fillers within polymer matrix are important factors for realizing various composite functionalities. Here, we describe an industrially scalable approach to preparing composites bearing highly aligned model hexagonal boron nitride filler (hBN) by simple melt-pressing. This outcome is achieved by using a malleable but thermal stiffening polymer matrix. The matrix maintains or even increases its stiffness during processing at elevated temperatures, producing the composites with highly aligned hBN and consequently a high thermal conductivity (28 W/mK). Furthermore, the composite bearing aligned hBN exhibits a 62% reduction in oxygen permeation with only 2.7 vol% of hBN. Since the matrix can be chemically depolymerized with an aid of acid, it is also possible to recover the hBN from the composite without physical/chemical denaturation of the filler, thus the recovered filler can be re-used in the future.

The confined self-assembly of block copolymers (BCPs) can be used to generate hierarchically structured composite microspheres. In this study, microspheres of gold-cored BCP (Au-BCP) spheres were first produced from an evaporative toluene-in-water-emulsion in which polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) BCPs incorporated with Au precursors (AuCl4–) were dissolved in toluene. Interestingly, the addition of cetyltrimethylammonium bromide (CTAB) into the microspheres resulted in the selective extraction of Au precursors within the Au-BCP spheres near the surface of the microsphere because of the strong electrostatic attraction between the CTAB and Au precursors. Therefore, regular-patterned porous nanostructures on the surface of Au-BCP microspheres were formed, of which the size could be varied by controlling the molecular weight of the PS-b-P4VP polymers. In addition, the depth of the pores could be modulated independently by tuning the amounts of Au precursors that were incorporated into the Au-B...

We report on the strong segregation of core–shell Au nanoparticles, with a shell layer consisting of a random copolymer brush of styrene and vinylphenol (PS-r-PVPh-SH), in poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) diblock copolymer. Because of the formation of multiple hydrogen bonds between the hydroxyl groups within the shell of the nanoparticles and the pyridine group in PS-b-P2VP, the Au nanoparticles were strongly localized into P2VP domains with a very high volume fraction of nanoparticles (ϕp ∼ 0.53). The spatial distribution of Au nanoparticles, observed by transmission electron microscopy (TEM), is compared with results of previous experiments where homopolymers were blended with block copolymers. If the diameter d of the nanoparticles is much less than the width D of the P2VP lamellar domains, these nanoparticles are more uniformly distributed across the P2VP domain than if d is comparable to D, in which case the nanoparticles are pushed toward the center of the P2VP domains. This behavior is ...

Polymeric bicontinuous morphologies were created by thermal annealing mixtures of poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) block copolymers and stabilized Au-core/Pt-shell (Au–Pt) nanoparticles. These Au–Pt nanoparticles have a cross-linked polymeric shell to promote thermal stability and are designed to adsorb strongly to the interface of the PS-b-P2VP block copolymer due to the favorable interaction between P2VP block and the exterior of the cross-linked shell of the nanoparticle. The interfacial activity of these Au–Pt nanoparticles under thermal annealing conditions leads to decrease in domain size of the lamellar diblock copolymer. As nanoparticle volume fraction ϕp was increased, a transition from a lamellar to a bicontinuous morphology was observed. Significantly, the effect of these shell-cross-linked Au–Pt nanoparticles under thermal annealing conditions was similar to those of traditional polymer grafted Au nanoparticles under solvent annealing conditions reported previously. These results su...

In this study, we developed a novel strategy to control the orientation of microdomains in block copolymer thin films by introducing either selective or neutral gold nanoparticles (Au NPs) that were thermally stable. The Au NPs were modified with thiol-terminated polymeric ligands, poly[(methyl methacrylate-r-styrene)-b-azidostyrene] (P[(MMA-r-S)-b-S-N3]-SH), having different compositions of methyl methacrylate (MMA) and styrene in P(MMA-r-S) block to precisely tune the interfacial interaction between the Au NPs and block copolymer template, poly(styrene-b-methyl methacrylate) (PS-b-PMMA). These Au NPs have a cross-linked polymeric shell, via UV cross-linking of P(S–N3) block, and thus were stable under thermal annealing at temperatures up to ∼200 °C. The selective Au NPs, which had 80 mol % PMMA in the P(MMA-r-S) block, were located within the PMMA domain of the PS-b-PMMA block copolymer. In contrast, the neutral Au NPs, which had 20 mol % PMMA in the P(MMA-r-S) block, were localized at the interface bet...

This work was supported by a grant (M102KN010001-02K1401-00212) from the Center for Nanoscale Mechatronics & Manufacturing of the 21st Century Frontier Research Program and by the Korean Ministry of Science and Technology through the Creative Research Initiatives Project. We also acknowledge partial support from the National R&D Project for Nano Science and Technology, Brain Korea 21 program, and CUPS-ERC.

In this work, we fabricated a designed 2D polymer pattern by embossing and replica molding using colloidal stamps that were prepared from self-assembled particle arrays in a soft, patterned PDMS mold. For a successful pattern transfer, polymer infiltration at the interstices between the silica spheres of the colloidal stamp was controlled by depositing a thin gold layer.

Onionlike block copolymer particles containing a well-ordered gold nanoparticle array were prepared with the help of amphiphilic block copolymer used as a surfactant. The location of gold nanoparticles ordered in the specific position of block copolymer domain was systematically investigated by tuning the invariant polymerization index of the block copolymer and the areal chain density (Σ) of gold nanoparticles.

A 2D hollow metal nanopillar array was fabricated using reactive ion etching through the silica nanosphere arrays self-organized over a polymeric film for higher etching contrast. The present approach is applicable to diverse hollow metal nanopillars.

We present a versatile strategy to prepare a range of nanostructured poly(styrene)-block-poly(2-vinyl pyridine) copolymer particles with tunable interior morphology and controlled size by a simple solvent exchange procedure. A key feature of this strategy is the use of functional block copolymers incorporating reactive pyridyl moieties which allow the absorption of metal salts and other inorganic precursors to be directed. Upon reduction of the metal salts, well-defined hybrid metal nanoparticle arrays could be prepared, whereas the use of oxide precursors followed by calcination permits the synthesis of silica and titania particles. In both cases, ordered morphologies templated by the original block copolymer domains were obtained.

A novel method was developed for the assembly of patterned binary and ternary particle arrays and their inverted pore structures onto V-shaped microchannels that were fabricated by soft lithography. For the ternary particle arrays and their inverted pore structures, a dip-coating of binary particle mixture with a controlled size ratio and subsequent O2 RIE were used.

We report localized surface plasmon resonance (LSPR) of hexagonal Au nanodot arrays to detect changes in the thickness and conformation of poly[2-(methacryloyloxy)ethyltrimethyl ammonium chloride] (PMETAC) brushes.

We demonstrate that colloidal lithography with self-assembled monolayers of crosslinkable polymeric particles can be used to create hierarchical arrays of nanopores on substrates.

Here, we demonstrate the preparation of a hybrid nanoplasmonic probe array, a nanoforest, which consists of gold nanostructures coated on top of silica nanospheres and evaporated gold film structure onto bottom through masks. Optically tunable plasmonic surfaces could be achieved by varying the nanoforest fabrication conditions, which acted as a selective nanoantenna. Plasmon coupling effects were effectively controlled by adjusting the vertical distance (nanogap) between the gold nanostructures on the silica bead and the bottom. Such control is critical to highly sensitive molecular detection applications. As a proof of concept, nanoforests were used as colorimetric sensors of refractive index changes. The sensors were highly sensitive and displayed distinct colors for small refractive index (RI) changes. The flexible and sensitive near/far-field optical properties render these nanoforests excellent plasmonic substrates for quantitative, sensitive and label-free sensing with nanoscale spatial resolution.