Self-Assembly of Ionizable “Clicked” P3HT-b-PMMA Copolymers: Ionic Bonding Group/Counterion Effects on Morphology

Electrode-modified block copoly-ionic liquid boosting the CO2 reduction toward CO in water-based media

Coupling polymer and ionic liquids with electrodes for catalysis is a promising tool for optimization of electrocatalytic CO₂ reduction reaction (CO₂RR). Here, block copolymer ionic liquids BCPILs were synthesized via controlled radical polymerization and nucleophilic post-substitution to introduce imidazole moieties. We show that, thanks to these PIL functionalities, the BCPIL/Re@HPC/GDL electrode can keep the selectivity toward CO when a higher amount of water is present in the electrolyte than the raw Re@HPC/GDL system. Our results help to understand the development of solid-state ionic liquids for enhanced CO₂RR in water-based electrolyte.

Robust Full-Spectral Color Tuning of Photonic Colloids

Creation of color through photonic morphologies manufactured by molecular self-assembly is a promising approach, but the complexity and lack of robustness of the fabrication processes have limited their technical exploitation. Here, it is shown that photonic spheres with full-color tuning across the entire visible spectrum can be readily and reliably achieved by the emulsification of solutions containing a block copolymer (BCP) and two swelling additives. Solvent diffusion out of the emulsion droplets gives rise to 20-150 µm-sized spheres with an onion-like lamellar morphology. Controlling the lamellar thickness by differential swelling with the two additives enables color tuning of the Bragg interference-based reflection band across the entire visible spectrum. By studying five different systems, a set of important principles for manufacturing photonic colloids is established. Two swelling additives are required, one of which must exhibit strong interactions with one of the BCP blocks. The additives should be chosen to enhance the dielectric contrast, and the formation kinetics of the spheres must be sufficiently slow to enable the emergence of the photonic morphology. The proposed approach is versatile and robust and allows the scalable production of photonic pigments with possible future applications in inks for cosmetics and arts, coatings, and displays.

Unidirectional Perpendicularly Aligned Lamella-Structured Oligosaccharide (A) ABA Triblock Elastomer (B) Thin Films Utilizing Triazolium+/TFSI- Ionic Nanochannels

We designed and synthesized high χ-low N-maltoheptaose-(triazolium+/N(SO2CF3)2-)-polyisoprene-(triazolium+/N(SO2CF3)2-)-maltoheptaose ABA triblock elastomers featuring triazolium+/N(SO2CF3)2- (TFSI-) counteranion ionic interfaces separating their constituting polymeric sub-blocks. Spin-coated and solvent-vapor-annealed (SVA) MH1.2k-(T+/TFSI-)-PI4.3k-(T+/TFSI-)-MH1.2k thin films demonstrate interface-induced charge cohesion through ca. 1 nm "thick" ionic nanochannels which facilitate the self-assembly of a perpendicularly aligned lamellar structure. Atomic force microscopy (AFM) and (grazing-incidence) small-angle X-ray scattering ((GI)SAXS) characterizations of MH1.2k-(T+/TFSI-)-PI4.3k-(T+/TFSI-)-MH1.2k and pristine triBCP analogous thin films revealed sub-10 nm block copolymer (BCP) self-assembly and unidirectionally aligned nanostructures developed over several μm2 areas. Solvated TFSI- counterions enhance the oligosaccharide sub-block packing during SVA. The overall BCP phase behavior was mapped through SAXS characterizations comparing di- vs triblock polymeric architectures, a middle PI sub-block with two different molecular masses, and TFSI- or I- counteranion effects. This work highlights the benefits of inducing single-point electrostatic interactions within chemical structures of block copolymers to master the long-range self-assembly of prescribed morphologies.

Correlating Optical Reflectance with the Topology of Aluminum Nanocluster Layers Growing on Partially Conjugated Diblock Copolymer Templates

Large-scale fabrication of metal cluster layers for usage in sensor applications and photovoltaics is a huge challenge. Physical vapor deposition offers large-scale fabrication of metal cluster layers on templates and polymer surfaces. In the case of aluminum (Al), only little is known about the formation and interaction of Al clusters during sputter deposition. Complex polymer surface morphologies can tailor the deposited Al cluster layer. Here, a poly(methyl methacrylate)-block-poly(3-hexylthiophen-2,5-diyl) (PMMA-b-P3HT) diblock copolymer template is used to investigate the nanostructure formation of Al cluster layers on the different polymer domains and to compare it with the respective homopolymers PMMA and P3HT. The optical properties relevant for sensor applications are monitored with ultraviolet-visible (UV-vis) measurements during the sputter deposition. The formation of Al clusters is followed in situ with grazing-incidence small-angle X-ray scattering (GISAXS), and the chemical interaction is revealed by X-ray photoelectron spectroscopy (XPS). Furthermore, atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) yield topographical information about selective wetting of Al on the P3HT domains and embedding in the PMMA domains in the early stages, followed by four distinct growth stages describing the Al nanostructure formation.

Modulating Microphase Separation of Lamellae-Forming Diblock Copolymers via Ionic Junctions

We present a molecular dynamics simulation study investigating the phase behavior of lamellae-forming diblock copolymers with a single ionic junction on the backbone. Our results show qualitative agreement with experimental findings regarding enhanced microphase separation with the introduction of an ionic junction at the conjunction point, while further revealing nonmonotonic changes in domain spacing and order-disorder transition as a function of the electrostatic interaction strength. This highlights the dominant roles of entropic and binding effects of counterions under weak and strong ionic correlations, respectively. The location of the ionic junction is found to effectively modulate the charge distribution and chain conformation in the ordered domains; its presence in the middle of a block promotes folding of the block, leading to a smaller domain size. These findings demonstrate the interplay of ionic coupling with steric hindrance and chain end effects, which enhances our understanding of the delicate control over the microphase domain features.

The size and affinity effect of counterions on self-assembly of charged block copolymers

The effect of counterions' size and affinity on the microphase separated morphologies of neutral-charged diblock copolymers is investigated systematically using a random phase approximation (RPA) and self-consistent field theory (SCFT). The phase diagrams as a function of χ_AB and f_A at different counterion sizes and different affinities to neutral blocks are constructed, respectively. Stability limits calculated using the RPA are in good agreement with the disorder-body-centered cubic phase boundaries from SCFT calculations. It was found that increasing the size of counterions causes the phase diagram to shift upward and leftward, which is attributed to electrostatic interactions and the intrinsic volume of counterions. The domain size of the ordered phase shows an unexpected tendency that it decreases with increasing counterions' size. The counterions' distributions in H and G phases demonstrate that it is electrostatic interaction, instead of packing frustration, that plays a leading role in such systems. For finite size counterions, with the increase in affinity between counterions and neutral blocks, the phase diagram shifts upward, indicating the improved compatibility between different blocks. Furthermore, the affinity effect between counterions and neutral blocks can be mapped into an effective Flory parameter χ_AB ^' = χ_AB + 0.27χ_BC.

Core@Corona Functional Nanoparticle-Driven Rod-Coil Diblock Copolymer Self-Assembly

Herein, a novel strategy to overcome the influence of π-π stacking on the rod-coil copolymer organization is reported. A diblock copolymer poly(3-hexylthiophene)-block-poly(ethylene glycol methyl ether methacrylate) (P3HT-b-PEGMA) was synthesized by the Huisgen cycloaddition, so-called "click chemistry", combining the PEGMA and P3HT blocks synthesized by atom transfer radical polymerization and Kumada catalyst transfer polymerization, respectively. Using a dip-coating process, we controlled the original film organization of the diblock copolymer by the crystallization of the P3HT block via π-π stacking. The morphology of the P3HT-b-PEGMA films was influenced by the incorporation of gold nanoparticles (GNPs) coated by poly(ethylene glycol) ligands. Indeed, the crystalline structuration of the P3HT sequence was counterbalanced by the addition in the film of gold nanoparticles finely localized within the copolymer PEGMA matrix. Transmission electron microscopy and time-of-flight secondary ion mass spectrometry analysis validated the GNP homogeneous localization into the compatible PEGMA phase. Differential scanning calorimetry showed the rod block crystallization disruption. A morphological transition of the self-assembly is observed by atomic force microscopy from P3HT fibrils into out-of-plane cylinders driven by the nanophase segregation.

Reactive nano-patterns in triple structured bio-inspired honeycomb films as a clickable platform

Towards unprecedented triple structured bio-inspired honeycomb film by selfassembly of a functional block copolymer during breath figure templating as a nano-patterned clickable platform.

Brush Polymer of Donor-Accepter Dyads via Adduct Formation between Lewis Base Polymer Donor and All Carbon Lewis Acid Acceptor

A synthetic method that taps into the facile Lewis base (LB)→Lewis acid (LA) adduct forming reaction between the semiconducting polymeric LB and all carbon LA C60 for the construction of covalently linked donor-acceptor dyads and brush polymer of dyads is reported. The polymeric LB is built on poly(3-hexylthiophene) (P3HT) macromers containing either an alkyl or vinyl imidazolium end group that can be readily converted into the N-heterocyclic carbene (NHC) LB site, while the brush polymer architecture is conveniently constructed via radical polymerization of the macromer P3HT with the vinyl imidazolium chain end. Simply mixing of such donor polymeric LB with C60 rapidly creates linked P3HT-C60 dyads and brush polymer of dyads in which C60 is covalently linked to the NHC junction connecting the vinyl polymer main chain and the brush P3HT side chains. Thermal behaviors, electronic absorption and emission properties of the resulting P3HT-C60 dyads and brush polymer of dyads have been investigated. The results show that a change of the topology of the P3HT-C60 dyad from linear to brush architecture enhances the crystallinity and Tm of the P3HT domain and, along with other findings, they indicate that the brush polymer architecture of donor-acceptor domains provides a promising approach to improve performances of polymer-based solar cells.

Hierarchical honeycomb-structured films by directed self-assembly in “breath figure” templating of ionizable “clicked” PH3T-b-PMMA diblock copolymers: an ionic group/counter-ion effect on porous polymer film morphology

Impact of the ionization of “clicked” rod–coil diblock copolymers on their directed self-assembly in “breath figure” templating for hierarchically honeycomb-structured films.