Ionic Assembly Research Articles

Growing polyion complex micelles: kinetics and mechanism of electrostatic template polymerization and assembly

HypothesisElectrostatic-templated polymerization (ETP) is a recently developed strategy for robust fabrication of stable polyion complex (PIC) micelles with regulated size and morphology, yet the kinetics and mechanism about this one pot process remain elusive. ExperimentsIn ETP method, ionic monomers are polymerized in the presence of an oppositely charged ionic-neutral diblock copolymer as template. We investigate the monomer conversion and electrostatic assembly as a function of time, under different polymerization conditions of ionic strength, pH, template/monomer molar ratio and the presence of a cross-linker. FindingsThe template copolymer accelerates the monomer conversion and formation of PIC micelles dependent on ionic strength and pH. The process follows the “Pick-up” mechanism, where monomers first convert into oligomers which complex with template to induce further chain growth and electrostatic assembly. Introducing cross-linker hardly impacts the reaction kinetics and “Pick-up” route, while it creates PIC micelles containing cross-linked ionic network assembly with the template. Further removing the template by concentrated salt provides purified ionic nanogels. The disclosed findings not only provide a better understanding of the polymerization-assembly process, but also optimize the controls of electrostatic-templated polymerization for the rational design and fabrication of diverse PIC micelles and polyelectrolyte particles.

Synthesis of biobased Phosphorus-Nitrogen-Silicon ceramizable flame retardant and its flame retardancy effects on EPS

The rising interest in eco-friendly flame retardants marks a notable trend in the industry. However, the challenge remains that most flame retardants, while achieving high flame retardant properties, struggle to balance environmental sustainability and resource utilization. This work delves into the green synthesis and mechanism of action of ceramizable flame retardants. Using phytic acid (PA) and urea (U) as raw materials, ionic complexation assembly in water, employing polydopamine (PDA) as an adhesive, to develop an environmentally friendly, bio-based synergistic flame retardant (PAU) is conducted. Building upon this groundwork, the addition of the ceramic filler kaolin (KL) and the fluxing agent sodium carbonate (Na2CO3) physically modifies the PAU, resulting in a novel eco-friendly, bio-based, ceramifiable flame retardant (PAUK). Employing the prepared PAUK through an effective surface coating technique, a lightweight and scratch-resistant flame-retardant expanded polystyrene insulation board (EPS-PAUK) is created. The best EPS-PAUK composite in our study exhibits an oxygen index of 52.5, achieves a V-0 UL-94 rating, and features excellent smoke suppression and compression strength up to 67.8 kPa, while nearly maintaining the lightweight characteristics of the EPS insulation boards. This bio-based, ceramifiable flame retardant system offers a new approach for producing lightweight, highly efficient flame-retardant and high-performance polymers.

Diversifying hierarchical ionic assembly by docking cations to anions as salt bridges

Diversifying hierarchical ionic assembly by docking cations to anions as salt bridges

Structural, spectroscopy, nonlinear optical, and laser damage threshold analyses of sodium guanidinium bis(4-methylbenzenesulfonate) hydrate (NGMBS) crystal

Sodium guanidinium bis(4-methylbenzenesulfonate) hydrate (NGMBS) crystallized in the monoclinic crystal system with non-centrosymmetric space group P21. The mixed ionic crystal assembly was stabilized by N H⋯O hydrogen bonding involving guanidinium ion and with Na+ ions surrounded by aqua ligands and S–O oxygen atoms completing six coordination involving with coordinate covalent and ion–dipole interactions. A supramolecular assembly in two dimensions (along the a and b-axis) is possible by H-bonding which brought the Na+ within a distance of 3.6493 Å. The two 4-methylbenzenesulfonate ligands in one formula unit were not identical and exhibited structural variations. Hirshfeld analyses indicated significant interaction due to N⋯H, O⋯H, and Na+ … O. The vibrational bands were ascertained using FTIR. A cut-off wavelength of 273 nm and bandgap of 4.50 eV were estimated from UV–visible spectroscopy. The compound excited at 260 showed emission at 291 nm. Colour purity up to 95.62 % was estimated from chromaticity calculations. Kurtz-Perry's method confirmed that NGMBS showed NLO properties 1.5 times than KDP. The NGMBS crystal demonstrated superior resistance to LASER induced damage as compared to urea.

Water-Stable, Eight-electron Acceptor Drives Anion⋅⋅⋅Water Assisted Tunable Ionic Self-Assembly and Proton Conduction.

Organic π-scaffolds are being envisaged for new-age electron- and ion-responsive materials that can accumulate electrons as well as transport proton. However, such systems are extremely rare as electron-deficient scaffolds are unstable in aqueous solution. Here we detail the synthesis of a water-stable core-naphthalenediimide-nitrobenzyl-viologen based tetra-cation, which accumulates up to eight-electrons within an exceptionally narrow potential window of +0.05 V and -1.12 V. The supramolecular interactions and the ensuing ionic framework are tunable based on the three anions, e. g., Cl-, Br- and PF6 -, that are investigated in this work. The ionic framework is formed and supported by a range of H-bonds, in which, the nitro benzyl groups act as pillars connecting the 1D water-tapes and the halide anions. The water molecules are hydrogen-bonded with the halide anions and bestow a facile pathway for the proton conduction, with proton conductivity up to 3.19×10-3 S cm-1. In contrast, the ionic assembly formed by the lipophilic PF6 - anions do not host the water tapes and consequently the proton conductivity is found to be four orders of magnitude lower. This is a unique example, whereby proton conductivity is realized and is tunable within a highly electron-deficient, eight-electron acceptor, water-stable ionic supramolecular system.

Ionic Liquid-Induced Assembly of DNA at Air-Water Interface.

DNA nanotechnology is the future of many products in the pharmaceutical and cosmetic industries. Self-assembly of this negatively charged biopolymer at surfaces and interfaces is an essential step to elaborate its field of applications. In this study, the ionic liquid (IL) monolayer-assisted self-assembly of DNA macromolecules at the air-water interface has been closely monitored by employing various quantitative techniques, namely, surface pressure-area (π-A) isotherms, surface potential, interfacial rheology, and X-ray reflectivity (XRR). The π-A isotherms reveal that the IL 1,3-didecyl 3-methyl imidazolium chloride induces DNA self-assembly at the interface, leading to a thick viscoelastic film. The interfacial rheology exhibits a notable rise in the viscoelastic modulus as the surface pressure increases. The values of storage and loss moduli measured as a function of strain frequency suggest a relaxation frequency that depends on the length of the macromolecule. The XRR measurements indicate a considerable increase in DNA layer thickness at the elevated surface pressures depending on the number of base pairs of the DNA. The results are considered in terms of the electrostatic and hydrophobic interactions, allowing a quantitative conclusion about the arrangement of DNA strands underneath the monolayer of the ILs at the air-water interface.

Poly(allylamine)-tripolyphosphate Ionic Assemblies as Nanocarriers: Friend or Foe?

Designing effective drug nanocarriers that are easy to synthesize, robust, and nontoxic is a significant challenge in nanomedicine. Polyamine-multivalent molecule nanocomplexes are promising drug carriers due to their simple and all-aqueous manufacturing process. However, these systems can present issues of colloidal instability over time and cellular toxicity due to the cationic polymer. In this study, we finely modulate the formation parameters of poly(allylamine-tripolyphosphate) complexes to jointly optimize the robustness and safety. Polyallylamine was ionically assembled with tripolyphosphate anions to form liquid-like nanocomplexes with a size of around 200 nm and a zeta potential of -30 mV. We found that nanocomplexes exhibit tremendous long-term stability (9 months of storage) in colloidal dispersion and that they are suitable as protein-loading agents. Moreover, the formation of nanocomplexes induced by tripolyphosphate anions produces a switch-off in the toxicity of the system by altering the overall charge from positive to negative. In addition, we demonstrate that nanocomplexes can be internalized by bone-marrow-derived macrophage cells. Altogether, these nanocomplexes have attractive and promising properties as delivery nanoplatforms for potential therapies based on the immune system activation.

Investigation of physicochemical drivers directing ionic liquid assembly on polymeric nanoparticles

AbstractIonic liquids (ILs) have emerged as promising biomaterials for enhancing drug delivery by functionalizing polymeric nanoparticles (NPs). Despite the biocompatibility and biofunctionalization they confer upon the NPs, little is understood regarding the degree in which non‐covalent interactions, particularly hydrogen bonding and electrostatic interactions, govern IL‐NP supramolecular assembly. Herein, we use salt (0‐1 M sodium sulfate) and acid (0.25 M hydrochloric acid at pH 4.8) titrations to disrupt IL‐functionalized nanoassembly for four different polymeric platforms during synthesis. Through quantitative 1H‐nuclear magnetic resonance spectroscopy and dynamic light scattering, we demonstrate that the driving force of choline trans‐2‐hexenoate (CA2HA 1:1) IL assembly varies with either hydrogen bonding or electrostatics dominating, depending on the structure of the polymeric platform. In particular, the covalently bound or branched 50:50 block co‐polymer systems (diblock PEG‐PLGA [DPP] and polycaprolactone [PCl]‐poly[amidoamine] amine‐based linear‐dendritic block co‐polymer) are predominantly affected by hydrogen bonding disruption. In contrast, a purely linear block co‐polymer system (carboxylic acid terminated poly[lactic‐co‐glycolic acid]) necessitates both electrostatics and hydrogen bonding to assemble with IL and a two‐component electrostatically bound system (electrostatic PEG‐PLGA [EPP]) favors hydrogen‐bonding with electrostatics serving as a secondary role.

Theoretical Investigation on the Metamaterials Based on the Magnetic Template-Assisted Self-Assembly of Magnetic-Plasmonic Nanoparticles for Adjustable Photonic Responses.

The assembly of artificial nano- or microstructured materials with tunable functionalities and structures, mimicking nature's complexity, holds great potential for numerous novel applications. Despite remarkable progress in synthesizing colloidal molecules with diverse functionalities, most current methods, such as the capillarity-assisted particle assembly method, the ionic assembly method based on ionic interactions, or the field-directed assembly strategy based on dipole-dipole interactions, are confined to focusing on achieving symmetrical molecules. But there have been few examples of fabricating asymmetrical colloidal molecules that could exhibit unprecedented optical properties. Here, we introduce a microfluidic and magnetic template-assisted self-assembly protocol that relies mainly on the magnetic dipole-dipole interactions between magnetized magnetic-plasmonic nanoparticles and the mechanical constraints resulting from the specially designed traps. This novel strategy not only requires no specific chemistry but also enables magnetophoretic control of magnetic-plasmonic nanoparticles during the assembly process. Moreover, the assembled asymmetrical colloidal molecules also exhibit interesting hybridized plasmon modes and produce exotic optical properties due to the strong coupling of the individual nanoparticle. The ability to fabricate asymmetrical colloidal molecules based on the bottom-up method opens up a new direction for the fabrication of novel microscale structures for biosensing, patterning, and delivery applications.

Microbial Fuel Cell Using a Novel Ionic Liquid-Type Membrane–Cathode Assembly for Animal Slurry Treatment and Fertilizer Production

The implementation of a microbial fuel cell for wastewater treatment and bioenergy production requires a cost reduction, especially when it comes to the ion exchange membrane part and the catalysts needed for this purpose. Ionic liquids in their immobilized phase in proton exchange membranes and non-noble catalysts, as alternatives to conventional systems, have been intensively investigated in recent years. In the present study, a new microbial fuel cell technology, based on an ionic liquid membrane assembly for CoCu mixed oxide catalysts, is proposed to treat animal slurry. The new low-cost membrane–cathode system is prepared in one single step, thus simplifying the manufacturing process of a membrane–cathode system. The novel MFCs based on the new low-cost membrane–cathode system achieved up to 51% of the power reached when platinum was used as a catalyst. Furthermore, the removal of organic matter in suspension after 12 days was higher than that achieved with a conventional system based on the use of platinum catalysts. Moreover, struvite, a precipitate consisting of ammonium, magnesium, and phosphate, which could be used as a fertilizer, was recovered using this membrane–cathode system.

Coiled-coil scallops (Chlamys farreri) peptide hydrogel with metal ionic and temperature tunable assembly

Self-assembly of peptides is a powerful method of preparing nanostructured materials. Peptides frequently utilize charged groups as a convenient switch for controlling assembly state by pH, ionic strength or temperature. In this study, the molecular properties and gel-forming ability of Chlamys farreri protein hydrolysates were studied. According to self-assembled theory, the presence of isoleucine at position ‘a’ and leucine at ‘d’ causes a switch between coiled-coil structures. Compared to P-2-CG, the components of α-helix (23.60 ± 0.56%) were changed into β-sheet (4.83 ± 2.86%) in the secondary structure of the hydrogel induced by ZnCl2. NMR siginals appeared at high field,which indicated hydrogen bonds were formed between P-2-CG and solvent environments at 20 °C. With temperature going up, the hydrogen bonds were broken and nanofibrils were changed into dense aggregates. We expected that P-2-CG could provide a new candidate for preparing metal-induced nanofibers or hydrogels with further applications in food industry.

Molecular Insight into the Effects of Clustering on the Dynamics of Ionomers in Solutions.

Ionizable groups tethered to polymers enable their many current and potential applications. However, these functionalities drive the formation of physical networks through clustering of the ionic groups, resulting in constrained dynamics of the macromolecules. Understanding the molecular origin of this hindrance remains a critical fundamental question, whose solution will directly impact the processing of ionizable polymers from molecules to viable materials. Here, using quasielastic neutron scattering accompanied by molecular dynamics simulations, segmental dynamics of slightly sulfonated polystyrene is studied in solutions as the cohesion of the ionic assemblies is tuned. We find that in cyclohexane the ionic assemblies act as centers of confinement, affecting dynamics both on macroscopic lengths and in the vicinity of the ionic assemblies. Addition of a small amount of ethanol affects the packing of the ionizable groups within the assemblies, which in turn enhances the chain dynamics.

Response of Sulfonated Polystyrene Melts to Nonlinear Elongation Flows

Ionizable polymers form dynamic networks with domains controlled by two distinct energy scales, ionic interactions and van der Waals forces; both evolve under elongational flows during their processing into viable materials. A molecular level insight of their nonlinear response, paramount to controlling their structure, is attained by fully atomistic molecular dynamics simulations of a model ionizable polymer, polystyrene sulfonate. As a function of increasing elongational flow rate, the systems display an initial elastic response, followed by an ionic fraction-dependent strain hardening, stress overshoot, and eventually strain-thinning. As the sulfonation fraction increases, the chain elongation becomes more heterogeneous. Flow-driven ionic assembly dynamics that continuously break and reform control the response of the system.

Ionic Strength-Dependent Assembly of Polyelectrolyte-Nanoparticle Membranes via Interfacial Complexation at a Water-Water Interface.

Complexation between oppositely charged nanoparticles (NPs) and polyelectrolytes (PEs) is a scalable approach to assemble functional, stimuli-responsive membranes. Complexation at interfaces of aqueous two-phase systems (ATPSs) has emerged as a powerful method to assemble these functional structures. Membranes formed at these interfaces can grow continuously to thicknesses approaching several millimeters and display a high degree of tunability via modification of solution properties such as ionic strength. To identify the membrane assembly mechanism, we study interfacial assembly in a prototypical dextran/PEG ATPS, in which silica (SiO2) NPs suspended in the PEG phase undergo interfacial complexation with poly(diallyldimethylammonium chloride) (PDADMAC) supplied in the dextran phase. Using a microfluidic device that facilitates sequential insertion of fluorescent and nonfluorescent PDADMAC, we observe a transition in the membrane growth mechanism with ionic strength. In the absence of added salt ([NaCl] = 0 mM) PDADMAC chains permeate through the existing membrane to complex with NPs on the PEG side of the membrane, leading to the formation of well-stratified structures. At elevated ionic strength ([NaCl] = 500 mM), this permeation mechanism is lost. Rather, the complexing species incorporate uniformly across the membrane. We attribute this transition to a rapid exchange of PE-counterion, NP-counterion, and PE/NP binding sites facilitated by an increase in extrinsically compensated charged groups on the NPs and PEs at high salinity. These PDADMAC/SiO2 NP membranes have tremendous potential for the formation of functional membranes, offering control over the internal structure and serving as an ideal system for the generation of targeted release systems.

3D‐Printed Stacked Ionic Assemblies for Iontronic Touch Sensors

AbstractSensing is the process of detecting and monitoring any physico‐chemical environmental parameters. Herein, new self‐powered iontronic sensors, which utilize touch‐induced ionic charge separation in ionically conductive hydrogels, are introduced for potential use in object mapping, recognition, and localization. This is accomplished using high‐resolution stereolithography (SLA) 3D printing of stacked ionic assemblies consisting of discrete compartments having different ion transport properties. The latter assemblies readily allow programming the output voltage magnitude and polarity by means of variations in ion type, charge density, and cross‐linking density within the iontronic device. Voltages of up to 70 mV are generated on application of compressive strains of as much as 50% (≈22.5 kPa), with the magnitude directly proportional to stress, and the polarity dependent on the sign of the mobile ion. As a proof‐of‐concept demonstration, the resulting touch sensors are integrated on the fingertip to enable the tactile feedback, mimicking the tactile perception of objects for recognition applications. In addition, it is proposed that streaming potential is the underlying mechanism behind the iontronic touch sensors. The electromechanical response is therein consistent with a streaming potential model.

Bioabsorbable Carboxymethyl Starch-Calcium Ionic Assembly Powder as a Hemostatic Agent.

In contrast to hemostatic fabrics, foams, and gels, hemostatic spray powders may be conveniently applied on narrow and complex bleeding sites. However, powdered hemostatic agents are easily desorbed from the bleeding surface because of blood flow, which seriously decreases their hemostatic function. In this study, the hemostatic performance of a bioabsorbable powder with decreased desorption was investigated. The proposed hemostatic powder (OOZFIXTM) is an ionic assembly of carboxymethyl starch and calcium. The microstructure and chemical properties of the hemostatic powder were analyzed. The hemostatic performance (blood absorption, blood absorption rate, and coagulation time), thromboelastography (TEG), rheology, adhesion force, and C3a complement activation of the OOZFIXTM were evaluated and compared with those of the carboxymethyl starch-based commercial hemostatic powder (AristaTM AH). The in vivo rat hepatic hemorrhage model for hemostasis time and bioabsorption of the OOZFIXTM showed quick biodegradation (<3 weeks) and a significantly improved hemostasis rate (78 ± 17 s) compared to that of AristaTM AH (182 ± 11) because of the reduced desorption. The bioabsorbable hemostatic powder OOZFIXTM is expected to be a promising hemostatic agent for precise medical surgical treatments.

Anisotropic polymer membranes retaining nanolayered hydrogen sulfate anions for enhanced anhydrous proton conduction

Ionic liquids bearing acidic anions are intrinsically proton-conductive but mechanically weak for device application. Maintaining ionic conductivities after solidifying ionic liquids by polymerization remains a challenge due to the restriction of ion mobility. In this work, nanolayered ionic membranes bearing aligned acidic hydrogen sulfate anions are prepared from ionic liquid crystals for enhanced anhydrous proton conduction. To obtain polymerizable smectic assemblies, 3-tetradecyl-1-vinyl-imidazolium hydrogen sulfate as monomer and 3, 3'-(decane-1,10-diyl) bis(1-vinyl-imidazolium) hydrogen sulfate as cross-linker are synthesized. In situ polymerization of the ionic assemblies in the smectic phase results in robust membranes retaining nanolayered acidic anions. The nanolayered ionic membranes exhibit tensile strengths up to 16.6 MPa and keep thermally stable at temperatures up to 220 °C. Anhydrous conductivity of the aligned ionic membrane reaches a maximum of 22 mS cm−1 and follows the Arrhenius law. A peak power density of 71.5 mW cm−2 is achieved at 110 °C for the fuel cell constructed from the nanolayered ionic membrane under non-humidified conditions.

Enhancement of photoactivity and cellular uptake of (Bu4N)2[Mo6I8(CH3COO)6] complex by loading on porous MCM-41 support. Photodynamic studies as an anticancer agent

The incorporation by ionic assembly of the hexanuclear molybdenum cluster (Bu 4 N) 2 [Mo 6 I 8 (CH 3 CO 2 ) 6 ] ( 1 ) in amino-decorated mesoporous silica nanoparticles MCM-41 , has yielded the new molybdenum-based hybrid photosensitizer 1@MCM-41 . The new photoactive material presents a high porosity, due to the intrinsic high specific surface area of MCM-41 nanoparticles (989 m 2 g −1 ) which is responsible for the good dispersion of the hexamolybdenum clusters on the nanoparticles surface, as observed by STEM analysis. The hybrid photosensitizer can generate efficiently singlet oxygen, which was demonstrated by using the benchmark photooxygenation reaction of 9,10-anthracenediyl-bis(methylene)dimalonic acid (ABDA) in water. The photodynamic therapy activity has been tested using LED light as an irradiation source (λ irr ~ 400–700 nm; 15.6 mW/cm 2 ). The results show a good activity of the hybrid photosensitizer against human cervical cancer (HeLa) cells, reducing up to 70 % their viability after 20 min of irradiation, whereas low cytotoxicity is detected in the darkness. The main finding of this research is that the incorporation of molybdenum complexes at porous MCM-41 supports enhances their photoactivity and improves cellular uptake, compared to free clusters. Incorporation of photoactive molybdenum complexes at porous MCM-41 supports enhance their photoactivity and improves cellular uptake. • A hexanuclear molybdenum cluster has been incorporated in amino-decorated mesoporous silica nanoparticles. • The new photoactive material can generate efficiently singlet oxygen upon illumination with white light. • The photodynamic therapy activity has been tested with HeLa cells, reducing up to 70 % their viability. • The incorporation of molybdenum complexes at porous supports enhances their photoactivity and improves cellular uptake.

Electroreduction of nitrogen with almost 100% current-to-ammonia efficiency.

In addition to its use in the fertilizer and chemical industries1, ammonia is currently seen as a potential replacement for carbon-based fuels and as a carrier for worldwide transportation of renewable energy2. Implementation of this vision requires transformation of the existing fossil-fuel-based technology for NH3 production3 to a simpler, scale-flexible technology, such as the electrochemical lithium-mediated nitrogen-reduction reaction3,4. This provides a genuine pathway from N2 to ammonia, but it is currently hampered by limited yield rates and low efficiencies4-12. Here we investigate the role of the electrolyte in this reaction and present a high-efficiency, robust process that is enabled by compact ionic layering in the electrode-electrolyte interface region. The interface is generated by a high-concentration imide-based lithium-salt electrolyte, providing stabilized ammonia yield rates of 150 ± 20 nmol s-1 cm-2 and a current-to-ammonia efficiency that is close to 100%. The ionic assembly formed at the electrode surface suppresses the electrolyte decomposition and supports stable N2 reduction. Our study highlights the interrelation between the performance of the lithium-mediated nitrogen-reduction reaction and the physicochemical properties of the electrode-electrolyte interface. We anticipate that these findings will guide the development of a robust, high-performance process for sustainable ammonia production.

Ordered Nanostructures in Thin Films of Precise Ion-Containing Multiblock Copolymers.

We demonstrate that ionic functionality in a multiblock architecture produces highly ordered and sub-3 nm nanostructures in thin films, including bicontinuous double gyroids. At 40 °C, precise ion-containing multiblock copolymers of poly(ethylene-b-lithium sulfosuccinate ester)n (PESxLi, x = 12 or 18) exhibit layered ionic assemblies parallel to the substrate. These ionic layers are separated by crystalline polyethylene blocks with the polymer backbones perpendicular to the substrate. Notably, above the melting temperature (Tm) of the polyethylene blocks, layered PES18Li thin films transform into a highly oriented double-gyroid morphology with the (211) plane (d211 = 2.5 nm) aligned parallel to the substrate. The cubic lattice parameter (agyr) of the double gyroid is 6.1 nm. Upon heating further above Tm, the double-gyroid morphology in PES18Li transitions into hexagonally packed cylinders with cylinders parallel to the substrate. These layered, double-gyroid, and cylinder nanostructures form epitaxially and spontaneously without secondary treatment, such as interfacial layers and solvent vapor annealing. When the film thickness is less than ∼3agyr, double gyroids and cylinders coexist due to the increased confinement. For PES12Li above Tm, the layered ionic assemblies simply transform into disordered morphology. Given the chemical tunability of ion-functionalized multiblock copolymers, this study reveals a versatile pathway to fabricating ordered nanostructures in thin films.