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Solvent-free supersoft elastomer is highly desirable for building photonic structures with significant stimuli-responsive color changes. We report supersoft elastic porous microspheres with vivid structural colors obtained via self-assembly of amphiphilic bottlebrush block copolymers at the water/oil interface templated by ordered water-in-oil-in-water double emulsions. The porous structure is composed of cross-linked bottlebrush polydimethylsiloxane (PDMS) as the supersoft elastic skeleton and bottlebrush poly(ethylene oxide) (PEO) as the internal responsive layer. The obtained microspheres show large reversible volume changes through well-controlled dehydration or hydration of PEO in response to salt ions in an aqueous environment. As a result, full-spectrum colors are obtained dependent on different salt concentrations. In-situ observation of color reflection of a microsphere indicates a gradual structural transition from the outside to the inside corresponding to migration of water molecules and salt ions. Moreover, rod-like bottlebrush PEO exhibits an anion-induced salting-out behavior different from that of random coil polymers. The significantly responsive behaviors of bottlebrush block copolymer (BBCP) assemblies in the presence of salt ions primarily rely on the supersoft elastic skeleton of the porous structure, providing a facile route to the creation of stimuli-responsive photonic materials by low-cost self-assembly methods.

Since the first discovery of spontaneous emulsification, the process has remained uncontrollable for centuries leading to unstable emulsion droplets with limited uses. Herein, by in situ observatio...

Binder-free mesoporous graphitic carbon composite films on polymer or metal substrates are attractive for high-surface-area electrodes to achieve superior device performances. However, rapid and large-area fabrication of such materials remains a significant challenge due to the harsh conditions required for the carbonization process. We report an efficient method that combines bottom-up precursor film assembly with photothermal processing using sub-millisecond light pulses generated from a xenon flash lamp. This approach enables the rapid carbonization and graphitization of precursor films over large areas at ambient bulk temperature to yield functional films while avoiding damage to the substrates. The films contain light-absorbing nanoparticles to convert light energy into heat, a block copolymer to template the porous structures via self-assembly, and phenol-fomaldehyde resin to form the carbon skeleton. Graphitic carbon nanoribbons embedded in a porous carbon matrix are created under mild conditions using iron nanoparticles as the catalyst during the millisecond photothermal process. The resulting composite films show excellent electrochemical properties and are demonstrated for use as high capacity lithium ion battery anodes.

Ultratrace quantitative detection based on fluorescence is highly desirable for many important applications such as environmental monitoring or disease diagnosis, which however has remained a great challenge because of limited and irregular fluorescence responses to analytes at ultralow concentrations. Herein the problem is circumvented via local enrichment and detection of analytes within a microsensor, that is, photonic porous microspheres grafted with aggregation-induced emission gens (AIEgens). The obtained microspheres exhibit dual structural and molecular functions, namely, bright structural colors and strong fluorescence. Large fluorescence quenching induced by nitrophenol compounds in an aqueous environment is observed at ultralow concentrations (10-12-10-8 mol/L), enabling quantitative detection at a ppb level (ng/L). This is achieved within a porous structure with good connectivity between the nanopores to improve analyte diffusion, an internal layer of poly(ethylene oxide) (PEO) for analyte enrichment via hydrogen bonding, and homogeneous distribution of AIEgens within the PEO layer for enhanced fluorescence quenching. The fluorescent porous microspheres can be readily obtained in a single step templated by well-ordered water-in-oil-in-water double emulsion droplets with AIE amphiphilic bottlebrush block copolymers as the effective stabilizer.

High transparency and toughness are prerequisites for sustainable polymers if they are to find wide application as alternatives to petroleum-based polymers. However, the utility of sustainable polymers such as commercially available polylactide (PLA) is limited by their inherent brittleness and high cost. Unfortunately, toughening PLA-based materials via cost-effective blending strategies without sacrificing transparency remains a challenge. Herein, we report a novel strategy involving active refractive index matching for creation of highly transparent and tough PLA blends. Specifically, we engineered the refractive index of a promising renewable poly(epichlorohydrin-co-ethylene oxide) elastomer by introducing polar ionic moieties via a simple chemical method, and we blended the resulting ionomers with PLA. The best blend showed an impact strength of > 80 kJ/m2, an elongation at break of 400%, and high transparency (90%). These characteristics are of great importance for potential applications such as packaging. Our strategy offers a versatile new way to prepare high-performance sustainable polymer materials with excellent transparency.

Artificial self-assembly systems typically exhibit limited capability in creating nature-inspired complex materials with advanced functionalities. Here, an effective co-assembly strategy is demonstrated for the facile creation of complex photonic structures with intriguing light reflections. Two different lipophilic and amphiphilic bottlebrush block copolymers (BCPs) are placed within shrinking droplets to enable a cooperative working mechanism of microphase segregation and organized spontaneous emulsification, respectively. Layer assemblies of the lipophilic BCP and uniform water nanodroplets stabilized by the bottlebrush surfactant are both generated, and co-assembled into a bridged lamellar structure with the alternating arrangement of layers and closely packed nanodroplet arrays. Janus microspheres with diverse dual optical characteristics are successfully fabricated, and reflected wavelengths of light are highly tunable simply by changing the formulation or molecular weight of BCP.

We report here a new strategy for facile functionalization of isotactic polypropylene (iPP) via click chemistry. iPP bearing trimethylsilyl (TMS) protected alkynyl groups was prepared through copolymerization of propylene with a small amount of functional α-olefins with a zirconocene complex/AliBu3/[Ph3C][B(C6F5)4] catalytic system. The obtained copolymers exhibited high molecular weights beyond 2.0 × 105 and unimodal molecular distributions, with comonomer incorporation in the range of 1 to 4 mol% while maintaining good isotacticity ([mmmm] > 94%). Functionalization of the copolymers was achieved via TMS deprotection and click reactions in one-pot, providing a facile and efficient route to scalable fabrication of iPPs with diverse functionalities and improved physical properties. For instance, polyethylene glycol (PEG) was successfully grafted onto iPP polymer chains with a weight percentage up to 71.1%. Consequently, the hydrophilicity of the resultant copolymer was remarkably enhanced as revealed by the three times larger swelling of PEG-functionalized iPP after soaking in water for only a few minutes.

Photonic pigment particles prepared via self-assembly have been suffering from their poor mechanical performances; i.e., they can easily be damaged and lose structural color under a compression for...

Self-assembly is important for creating photonic structures and structural color is typically tunable by varying the size of building blocks, which are themselves obtained after time-consuming chemical syntheses. The molecular conformation of bottlebrush block copolymers (BBCPs) in solution can be manipulated to create libraries of photonic structures. Amphiphilic BBCPs bearing oxidation-responsive ferrocene groups on the hydrophilic block are used to fabricate porous particles via evaporation-induced self-assembly of water-in-oil-in-water (W/O/W) double emulsions stabilized by the BBCP surfactant. In situ oxidation of the ferrocene groups by hydrogen peroxide at the W/O interface leads to enhanced hydrophilicity, more hydration, and chain extension of the hydrophilic block. Consequently, larger internal water droplets are spontaneously formed, yielding larger pores within the microparticles. The pore diameter is readily tunable from 144 to 301 nm with a single BBCP, thereby generating full-spectrum structural colors. This work provides a straightforward method for fabrication of libraries of photonic pigments in an easy and scalable manner.

Photonic materials with angular independent structural colour are highly desirable because they offer the broad viewing angles required for application as colorants in paints, cosmetics, textiles or displays. However, they are challenging to fabricate as they require isotropic nanoscale architectures with only short-range correlation. In this article, porous microparticles with such a structure are produced in a single, scalable step from an amphiphilic bottlebrush block copolymer. This is achieved by exploiting a novel controlled micellization self-assembly mechanism within emulsified toluene-in-water droplets. By restricting water permeation through the droplet interface, the size of the pores can be precisely addressed, resulting in structurally coloured pigments. Furthermore, the reflected colour can be tuned to reflect across the full visible spectrum using only a single polymer (Mn = 290 kDa) by altering the initial emulsification conditions. Such photonic pigments have several key advantages over their crystalline analogues, as they provide isotropic structural coloration that suppresses iridescence and improves colour purity without the need for either refractive index matching or the inclusion of a broadband absorber., 32 pages, 18 figures, 1 table

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 ...

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...

Copolymerization is an effective strategy to regulate the molecular structure and tune crystalline structures. In this work, novel butene-1 copolymers with different polyethylene glycol (PEG) grafts (number-average molecular weight Mn = 750, 2000, and 4000 g/mol) were synthesized, for the first time introducing long-chain grafts to the polybutene-1 main chain. For these PEG-grafted copolymers, crystallization, melting, and phase transition behaviors were explored using differential scanning calorimetry. With respect to the linear homopolymer, the incorporation of a trimethylsilyl group decreases the cooling crystallization temperature (Tc), whereas the presence of the long PEG grafts unexpectedly elevates Tc. For isothermal crystallization, a critical temperature was found at 70 &deg, C, below which all polyethylene glycol-grafted butene-1 (PB-PEG) copolymers have faster crystallization kinetics than polybutene-1 (PB). The subsequent melting process shows that for the identical crystallization temperature, generated PB-PEG crystallites always have lower melting temperatures than that of PB. Moreover, the II-I phase transition behavior of copolymers is also dependent on the length of PEG grafts. When form II, obtained from isothermal crystallization at 60 &deg, C, was annealed at 25 &deg, C, PB-PEG-750, with the shortest PEG grafts of Mn = 750 g/mol, could have the faster transition rate than PB. However, PB-PEG-750 exhibits a negative correlation between transition rate and crystallization temperature. Differently, in PB-PEG copolymers with PEG grafts Mn = 2000 and 4000 g/mol, transition rates rise with elevating crystallization temperature, which is similar with homopolymer PB. Therefore, the grafting of the PEG side chain provides the available method to tune phase transition without sacrificing crystallization capability in butene-1 copolymers.

Hierarchical, structurally colored materials offer a wide variety of visual effects that cannot be achieved with standard pigments or dyes. However, their fabrication requires simultaneous control over multiple length-scales. Here we introduce a robust strategy for the fabrication of hierarchical photonic pigments via the confined self-assembly of bottlebrush block copolymers within emulsified microdroplets. The bottlebrush block copolymer self-assembles into highly ordered concentric lamellae, giving rise to a near perfect photonic multi-layer in the solid-state, with reflectivity up to 100%. The reflected color can be readily tuned across the whole visible spectrum by either altering the molecular weight or by blending the bottlebrush block copolymers. Furthermore, the developed photonic pigments are responsive, with a selective and reversible color change observed upon swelling in different solvents. Our system is particularly suited for the scalable production of photonic pigments, arising from their rapid self-assembly mechanism and size-independent color.

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-mercapto...

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 ...

For well-ordered block copolymer (BCP) nanocomposites containing nanoparticles (NPs), the ratio of NP core diameter (dcore) and BCP domain width (L) has been generally limited with dcore/L < 0.3 when NP/BCP interactions are relatively neutral or weak. Here, we systematically investigate the spatial distribution of gold nanoparticles (NP) ranging in size up to 0.8 times that of the target domain width in symmetric polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) using a hydrogen-bonding-mediated (H-bonding) assembly. NPs with core diameters (dcore) 2, 5, 9, and 15 nm are coated with ligands bearing phenol groups as the hydrogen-donating sites for H-bonding including 2-(11-mercaptoundecyl)hydroquinone and thiol-terminated poly(4-hydroxystyrene). These hydroxylated NPs are selectively incorporated into the P2VP block (domain width L = 7–37 nm) over a wide range of volume fractions (ϕ = 3–26 vol %). Particle distributions are biased toward the center of in the P2VP domains when dcore/L is greater than 0.3 and ...

Photonic crystals (PhCs) prepared using the self-assembly of block copolymers (BCPs) offer the potential for simple and rapid device fabrication but typically suffer from low refractive index contrast (Δn ≤ 0.1) between the phase-segregated domains. Here, we report the simple fabrication of BCP-based photonic nanocomposites with large differences in refractive index (Δn0.27). Zirconium oxide (ZrO2) nanoparticles coated with gallic acid are used to tune the optical constants of the target domains of self-assembled (polynorbornene-graft-poly(tert-butyl acrylate))-block-(polynorbornene-graft-poly(ethylene oxide)) (PtBA-b-PEO) brush block copolymers (BBCPs). Strong hydrogen-bonding interactions between the ligands on ZrO2 and PEO brushes of the BBCPs enable selective incorporation and high loading of up to 70 wt % (42 vol %) of the ZrO2 nanoparticles within the PEO domain, resulting in a significant increase of refractive index from 1.45 to up to 1.70. Consequently, greatly enhanced reflection at approximately 398 nm (increases of ∼250%) was observed for the photonic nanocomposites (domain spacing = 137 nm) relative to that of the unmodified BBCPs, which is consistent with numeric modeling results using transfer matrix methods. This work provides a simple strategy for a wide range tuning of optical constants of BCP domains, thereby enabling the design and creation of high-performance photonic coatings for various applications. The large refractive index contrast enables high reflectivity while simultaneously reducing the coating thickness necessary, compared to pure BCP systems.