PS Chains Research Articles

Influence of charge on conformations, inter-molecular structure and thermodynamics of symmetric polystyrene-block-polymethacrylic acid (PS-b-PMA) polyelectrolyte micelle in aqueous solution

ABSTRACT The various aspects of molecular structure, kinetics, and thermodynamics of symmetric polystyrene-b-poly(methacrylic acid) (PS-b-PMA) block copolymer micelle in salt-free aqueous solution as a function of degree-of-ionisation (f) of PMA (corona) block was investigated by explicit molecular dynamics (MD) simulations. Micelle size increases linearly with f in a qualitative agreement with simulation results in the literature. With increase in charge density of the corona-forming PMA chain block, the micelle becomes more spherical, and there is a decrease in the surface area of micelle core and an increase in the favourable interactions among the PS chains. The structure of the micelle changes with f. The behaviour of the RDF’s of core and corona PMA atoms and the enthalpy of solvation show that the interactions among the segments of the core PS blocks are insensitive to variation in f. The atom density profiles, solvation enthalpy, and coordination number of PMA-Na+ and Water-Na+ pairs reveal the existence of the micelle in the ‘osmotic regime’ in agreement with results from experiments and mean-field theory in literature. The significance of electrostatic interactions on the kinetics of formation, structural aspects, and thermodynamics of micellisation is shown. The characteristics of PMA-b-PS micelle are compared with those of PAA-b-PS.

Interfacial molecular structure and orientation evolution of the polystyrene under confinement during annealing revealed by sum frequency generation vibrational spectroscopy

The geometrical confinement directly affects many crucial properties of polymer thin films by interfacial interactions. A key to understanding the role of these interfacial interactions is to specifically probe the confined interface at the molecular level and in situ. However, the direct and nondestructive detection of interfacial polymer structures under confinement is very difficult. In this study, specific interface-sensitive sum frequency generation (SFG) spectroscopy was applied to study the deuterated PS (d8-PS) film confined between hydrogenated poly (methyl methacrylate) (PMMA) films at the molecular level and in situ. The results showed that the ordering/orientation of the PS chain (backbone and phenyl group) evolved at the buried d8-PS/PMMA interface during annealing. The tilt angle of the PS phenyl group increased while the twist angle decreased with elevated annealing temperature. Both overall SFG ssp and ppp intensities decreased after annealing at 433 K for 24 h, indicating that PS chains entangled with or penetrated the PMMA chains at the confined interface. This study qualitatively and quantitatively revealed the interfacial structure and structural evolution of the PS chain confined between PMMA films in situ during annealing, which is beneficial to the molecular-level understanding of the interfacial chain conformational relaxation of polymers under confinement.

The iron matters: Aged microplastics disrupted the iron homeostasis in the liver organoids

Plastic products undergo artificial and unintentional aging during daily use, causing the presence of aged microplastics (aMP). Humans are inevitably exposed to aMP. Liver is one of the critical target organs of MP through oral intake, however, limited research has focused on the hepatic toxicity of aMP compared to pristine MP (pMP). We utilized the human pluripotent stem cells-derived liver organoids (LOs) to compare the cytotoxicity of pristine polystyrene microplastics (pPS) (1 μm, carbonyl index 0.08) and aged polystyrene microplastics (aPS) (1 μm, carbonyl index 0.20) ranged from 20 to 200 ng/mL.Our findings indicate that aPS was more cytotoxic than pPS. We explored the disrupted iron homeostasis in terms of the [Fe2+] and [Fe3+] levels, iron storage and transport. A “vector-like effect” induced by aPS has been preliminarily suggested by the correlated change in total iron level and co-localization of PS and ferritin light chain (FTL) in the LOs following exposure to aPS and ferric ammonium citrate (FAC) individually and combinedly. In addition, we observed abnormal mitochondrial morphology, elevated lipid peroxidation, and declined GSH peroxidase activity, together with the declined expression of transferrin receptor (TFRC) and elevated expressions of SLC7A11, FTL. The gene handled iron transport and iron use were disrupted by aPS. Moreover, we employed FAC to introduce iron overload and Nacetylcysteine (NAC) to protect the lipid peroxidation. In aPS + FAC group, aggravated effects could be observed in aspects of [Fe2+] level, lipid peroxidation, and compromised expression levels of iron homeostasis-related markers, in contrast, in aPS + NAC group, most of changes recovered but the hepatocytoxicity remained. Specifically, a dimorphic change in elevated FTL and decreased ferritin heavy chain (FTH1) caused by 50 ng/mL aMP (57.33 ± 3.57 items/mL, equivalent to human intake level), indicated a specific response to low-dose aMP.

Building Porous Ni(Salen)-Based Catalysts from Waste Styrofoam via Autocatalytic Coupling Chemistry for Heterogeneous Oxidation with Molecular Oxygen.

The development of robust and industrially viable catalysts from plastic waste is of great significance, and the facile construction of high performance heterogeneous catalyst systems for phenol-quinone conversions remains a grand challenge. Herein, a feasible strategy is demonstrated to reclaim Styrofoam into hierarchically porous nickel-salen-loaded hypercrosslinked polystyrene (PS@Ni-salen) catalysts with high activities through an unusual autocatalytic coupling route. The salen is immobilized onto PS chain by Friedel-Crafts alkylation of benzyl chloride derivatives, and the generated hydrogen chloride coordinately promotes the simultaneous crosslinking and bridge formation between aromatic rings via a Scholl coupling route, leading to hierarchically porous networks. After the metallization with Ni, the resultant networks exhibit high catalytic activity for the oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethyl-1,4-benzoquinone under mild conditions (303 K, 1bar of O2 ). This catalyst also demonstrates attractive recycling performance without an obvious loss of catalytic efficiency over five consecutive cycles. This methodology might provide a potential sustainable alternative to construct environmentally benign and cost-effective catalysts for specific organic transformation.

Interfacial Engineering of Block Copolymer Nanostructures: Morphology and Solvent Stability.

Interfacial engineering is a critical pathway for modulating the self-assembled nanostructures of block copolymers (BCPs) during solvent exchange. Herein, we demonstrated the generation of different stacked lamellae of polystyrene-block-poly(2-vinyl pyridine) (PS-b-P2VP) nanostructures during solvent exchange by using phosphotungstic acid (PTA) or PTA/NaCl aqueous solution as the nonsolvent. The participation of PTA in the confined microphase separation of PS-b-P2VP in droplets increases the volume fraction of P2VP and decreases the tension at the oil/water interface. Moreover, the addition of NaCl to the PTA solution can further increase the surface coverage of P2VP/PTA on droplets. All factors impact the morphology of assembled BCP nanostructures. In the presence of PTA, ellipsoidal particles composed of alternatively stacked lamellae of PS and P2VP were formed (named BP), whereas, in the coexistence of PTA and NaCl, they changed to stacked disks with PS-core-P2VP-shell (called BPN). The different structures of assembled particles induce their different stabilities in solvents and different dissociation conditions as well. The dissociation of BP particles was easy because PS chains were only entangled together which can be swollen in toluene or chloroform. However, the dissociation of BPN was hard, requiring an organic base in hot ethanol. The structural difference in BP and BPN particles further extended to their dissociated disks, which makes the cargo (like R6G) loaded on these disks to show a different stability in acetone. This study demonstrated that a subtle structural change can greatly affect their properties.

Regulating the Flow-Driven Translocation of Macromolecules through Nanochannels by Interfacial Physical Adsorption

By using a model system composed of an anodic aluminum oxide nanopore (AAO), poly(benzyl acrylate) (PBAN) adsorbent, and polystyrene (PSN) probe, where N represents the degree of polymerization, this work has explored how the physical adsorption of PBA onto the surface of the AAO nanopore (rp ≈ 10 nm) influences the flow-driven translocation of PS in toluene. In the low flow rate range (Q = 0.02 mL/h), the translocation of PS chains is purely diffusive, and the partially reversible adsorption behavior of PBAN is observed only when N < ∼360, showing a strong chain length dependence. In the partially reversible regime, the interfacial thickness (δ) of the adsorption layer is estimated to be from ∼1.5 to ∼2.9 nm depending on the chain length. In the mixed solutions, when N increases from 0 to 75 and 150 for PBAN, the cut-off size (COS) of the membrane for broadly distributed PSB-285K (Mw/Mn ≈ 2.48) is estimated to decrease from ∼10.0 to ∼8.0 and ∼6.0 nm, respectively; in addition, the introduction of PBA360 can promote the separation of narrowly distributed PS655 and PS1200 by regulating re, whereas in the high flow rate range (Q > 0.02 mL/h), the translocation for PS long chains is based on the mechanism of molecular deformation, and the flow rate-dependent translocation shows a strong dependence on the chain length of PBAN. Namely, in mixed solutions, when N increases from 150 to 360, the critical flow rate (Qc) is found to slightly increase from ∼0.30 to ∼0.45 mL/h for PS1500 translocation; in addition, the cut-off performance of PSB-285K displays dependence both on flow rate and PBAN chain length. Our result has demonstrated a novel strategy to regulate the cut-off performance during the translocation of (bio)macromolecules through nanopores via partially reversible interfacial physical adsorption.

Synthesis of Polymer Brushes and Removable Surface Nanostructures on Tannic Acid Coatings

Polymer brushes refer to polymer chains that are end-grafted to surfaces or interfaces at high grafting density. Polymer brushes are able to make surface self-assembly or surface coassembly with free block copolymer (BCP) chains, and surface nanostructures with different morphologies are formed on the surfaces. The formation of the surface nanostructures endows materials with new surface properties. To develop a simple and versatile approach to the synthesis of polymer brushes and surface nanostructures, the synthesis of polymer brushes and surface nanostructures on tannic acid (TA) coatings was investigated in this research. TA molecules were coated on the surfaces of amino-modified silica particles (SiO2-NH2) through noncovalent bonds. Quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (qPDMAEMA-b-PS) chains were anchored onto the TA coatings through electrostatic interaction between qPDMAEMA blocks and TA coatings, and PS brushes are formed on the particle surfaces. Thermo gravimetric analysis demonstrates the grafting of the BCP chains on the TA coatings, and the calculation results indicate that the PS chains on the silica particles are in the polymer brush regime. PS brushes on TA coatings are able to make surface coassembly with free BCP chains, and surface nanostructures with different sizes and morphologies are produced on TA coatings. The grafting density of PS blocks and BCP concentration both exert significant influences on the formation of the surface nanostructures. The surface nanostructures can be removed from the particle surfaces in the aqueous solution of sodium chloride. This research provides a simple and versatile method for the fabrication of polymer brushes and removable surface nanostructures on any solid substrates, which have specific interactions with TA molecules.

Dynamic co-assembly behaviors of polyoxometalates and giant surfactants in dual solvents

Inorganic-organic hybridization is a widely used method to develop new functional materials involving polyoxometalates (POMs), affording them with unique synergistic physical and chemical properties. As one of the core topics in hybrid materials, the study of their assembly structures is critical for the optimization of their performances.In the present work, dynamic co-assembly behaviors of several giant surfactants XPOSS-PS (X, POSS and PS denote different polar groups, polyhedral oligomeric silsesquioxane and polystyrene, respectively) and Keggin-type silicotungstic acid H4SiW12O40 (H4SiW for short) were investigated. We designed and synthesized three series of giant surfactants that possess heads bearing cationic (NPOSS-PS, N for ammonium group), neutral (DPOSS-PS, D for dihydroxyl group) and anionic charges (APOSS-PS, A for carboxylic acid group), respectively. The different charge types of POSS heads lead to different electrostatic interactions with the anionic POM clusters, resulting in different co-assembly structures in dual mixed solvents. Moreover, we found the POM's loading content and PS chain length are another two important factors that can determine the morphology of co-assembly structures. This work expands the scope of co-assembled structures of POM-based hybrid materials, and provides a platform for the study of the basic physical principles of their co-assembly behaviors.

Effects of macromonomer chain length, solvent and concentration on the cyclization kinetics during AB-type step-growth polymerization

For the first time, this work has explored the cyclization kinetics of multi-mers during step-growth polymerization by using alkyne-PS-azide (l-PS-N3) as model macromonomer, where PS represents polystyrene. First, three AB-type PS macromonomers with different chain lengths have been prepared by atom transfer radical polymerization (ATRP), namely, l-PS77-N3, l-PS240-N3 and l-PS380-N3. Second, the polymerization and cyclization kinetics has been monitored in dimethylformamide (DMF), tetrahydrofuran (THF) and cyclopentane (CyP). Third, by size exclusion chromatography (SEC) and liquid chromatography at the critical condition (LCCC) methods, we have quantified how the macromonomer chain length, solvent type and reaction concentration affect the intra-chain cyclization process. The analysis results have demonstrated that, for macromonomer l-PS77-N3 with shorter chain length, the reaction rate of macromonomer cyclization, multi-mer cyclization and inter-chain coupling, is significantly faster than that for l-PS240-N3 and l-PS380-N3 with longer chain lengths. The total percentage of final cyclic product (wtcyclic) slightly decreases with the increase of macromonomer chain length, namely, 33%, 25% and 23% for l-PS77-N3, l-PS240-N3 and l-PS380-N3, respectively. At the same time, we found that, solvent with lower solvent viscosity and relatively poor solvent quality is more conducive to the cyclization reaction of PS chains. In addition, we also found that the inter-chain and intra-chain reaction rate are both faster than that at other reaction concentrations when the reaction concentration is near the critical overlapping concentration.

Computational and experimental studies on the micellar morphology and emission mechanisms of AIE and H-bonding fluorescent composites.

In this work, we use density functional theory (DFT) calculated competitive hydrogen bonds and dissipative particle dynamics (DPD) simulated micellar structural information to uncover the CO2-expanded liquid (CXL)-aided self-assembled structure and emission mechanisms of the self-assembled fluorescent composites (SAFCs). Herein, the SAFCs are formed through the self assembly between diblock copolymer polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) blend and the dye molecule 4-(9-(2-(4-hydroxyphenyl)ethynyl)-7,10-diphenylfluoranthen-8-yl)phenol (4) in CO2-expanded toluene at 313.2 K and varied pressures. Firstly, from DPD simulation, we have demonstrated that the addition of CO2 to toluene favors both the expansion of the solvophobic P4VP phase and contraction of solvophilic PS chains, which facilitates the continuous morphological transitions of SAFCs from spherical micelles (3.0 MPa) through wormlike plus spherical micelles (4.0-4.8 MPa) to large vesicles (6.0-6.5 MPa) with pressure rise. Secondly, the DFT calculated bonding energies and IR spectra of the competitive hydrogen bonds help us to clarify the major type of hydrogen bonds determining the fluorescence (FL) performance of the SAFCs. Furthermore, we have revealed the SAFC emission mechanism via the pressure-tunable changes in the aggregation degrees and amount of hydrogen bonds involving 4 and P4VP chains. This work provides a good understanding for the morphology-property control of the self-assembled polymer composites in both microscopic and mesoscopic scales.

Development of a Parallel Robotic Positioning System With Specific Workspace for Noninvasive Brain Stimulation

Brain stimulation using noninvasive methods has been widely adopted in neuropsychiatric disorder therapies. Clinicians who use the innovative methods situate the stimulator manually in a typical setup. However, this causes practical difficulties in precisely locating the stimulation device at a desired pose. This article proposes a robotic positioning system that can precisely position a brain stimulation device at the desired pose. The design concepts are focused on the development of a system with a workspace specialized in noninvasive brain stimulation. To stimulate the overall area around the upper part of the head, the system is designed to have a specific posture with a six-degrees-of-freedom (6-DOF) movable parallel mechanism and a 1-DOF extra revolute joint. The combined system not only significantly increases the workspace of the system but also increases its physical safety. In the movable parallel mechanism, we realize sufficient mobility for the robotic device using three- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bar{\bf{P}}}$</tex-math></inline-formula> <underline xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</u> PS chains ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bar{\bf{P}}}$</tex-math></inline-formula> : curved prismatic joint, R: revolute joint, P: prismatic joint, and S: spherical joint). The curved prismatic joint ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bar{\bf{P}}}$</tex-math></inline-formula> ) is a revolute joint realized by curved rail and enables efficient movement of the stimulator around the subject's head. Furthermore, the parallel mechanism offers good physical safety and load-carrying capacity. The moving platform, which is close to the head, exhibits low inertia, and there is no rapid change in the acceleration due to the failure of control because the moving platform is moved as a combination of joint movements. The system can accommodate stimulators of varying weights, such as those employing transcranial magnetic stimulation and ultrasound transducers. A prototype of the proposed system was developed using the design specifications, and its performance was verified experimentally.

Synthesis and properties of ABA type triblock copolymer from poly(dimethylsiloxane) macroinitiator: Development of novel attachable initiators for atom transfer radical polymerization

A sequence of ABA-type polystyrene-b-poly(dimethylsiloxane)-b-polystyrene (PS-b-PDMS-b-PS) triblock copolymers were synthesized by ATRP (Atom Transfer Radical Polymerization) after appropriate end functionalization of vinyl terminated PDMS. Vinyl terminated PDMS was reacted with a 3-chloropropane thiol to synthesize a halo terminated macroinitiator. Subsequently, this macroinitiator was used to synthesize ABA-type block copolymers. The resulting block copolymers were characterized to confirm the presence of PDMS & PS blocks. The theoretical molecular weight and GPC was used to verify the high molecular weight of the ultimate block copolymer. The results show that the PS chains were successfully bound to the PDMS backbone and molecular weight linearly increased with time during the controlled polymerization. The functionality of the given polymer was confirmed by FT-IR analysis, 1H NMR, and 13C NMR spectra. The thermal stability increased after the addition of PS with PDMS. Additionally, the EDS analysis confirms the halogen content. DLS verified the particle size, whereas SEM was used for the morphology of the nanoaggregates. This triblock has good moisture resistance & thermal stability as determined by thermogravimetric analysis. The formation of PDMS blocks increased the hydrophobicity of the PS and contact angle analysis confirmed this.

A colorimetric detection of polystyrene nanoplastics with gold nanoparticles in the aqueous phase

Nanoplastics has become a growing environmental concern because these tiny particles can easily penetrate biological tissues and have possible toxic effects. FT-IR and Raman spectroscopy methods are currently used to analyze microplastics (5 mm or less), but they encounter difficulty when the particles are below 1 μm. On the other hand, thermoanalysis of nanoplastics does not provide the size information. Therefore, herein, we proposed the colorimetric detection method with gold nanoparticles (AuNPs) to measure the concentration of polystyrene nanoplastics (PSNPs, size = 350 and 880 nm) through a color change that is obvious to the naked eye. A mixed dispersion of PSNPs and AuNPs was added with acetone, a good solvent for polystyrene. In this colorimetric detection, acetone acted as a key component to enhance or hinder the aggregation of AuNPs around PSNPs. Namely, acetone itself promoted AuNPs aggregation, but it was dissolved partially PS chains from PSNSs to act as inhibitor of aggregation of AuNPs. These two contradictory feature of acetone to AuNPs and PSNPs affect the aggregation and color of AuNPs (dispersed = red, aggregated = blue). Finally, the heat-map between PSNSs and acetone was prepared to use for estimation of concentration of PSNPs in the aqueous solution with naked eye. To the best of our knowledge, this is the first attempt to measure nanoplastics by colorimetry.

Core–Satellite Micelles by a Linear A1B1A2B2 Tetrablock Copolymer

Block copolymers in water or compatible solvents show micelles with various shapes, such as worm-like, vesicles, and spheres. In this study, we prepared core–satellite micelles by employing a polystyrene-block-polyisoprene-block-polystyrene-block-polyisoprene (S1I1S2I2) linear tetrablock copolymer. When a PS-compatible solvent, for example, dimethylacetamide or diethylphthalate, is used, the PI chains form the inside core, while the PS chains become a shell as long as the volume fraction of mid PI1 chains (fPI1) is large enough (0.2) to form a loop configuration, resulting in merging into spherical cores consisting of the PI2 chains. However, at smaller fPI1 (0.08), the short mid PI1 chains cannot merge into the PI2 core and therefore exist separately as small spherical micelles, which are referred to as the “satellite” micelles. Thus, the micelles consist of large central core spheres and smaller outside satellite spherical micelles.

Solvent Annealing of Striped Ellipsoidal Block Copolymer Particles: Reversible Control over Lamellae Asymmetry, Aspect Ratio, and Particle Surface.

Solvent annealing is a versatile tool to adjust the shape and morphology of block copolymer (BCP) particles. During this process, polar solvents are often used for block-selective swelling. However, such water-miscible solvents can induce (partial) solubilization of one block in the surrounding aqueous medium, thus, causing complex structural variations and even particle disassembly. To reduce the complexity in morphology control, we focused on toluene as a nonpolar polystyrene-selective solvent for the annealing of striped polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) ellipsoids. The selective stretching of PS chains produces unique asymmetric lamellae structures, which translate to an increase in the particle aspect ratio after toluene evaporation. Complete reversibility is achieved by changing to chloroform as a nonselective solvent. Moreover, surfactants can be used to tune block-selective wetting of the particle surface during the annealing; for example, a PS shell can protect the internal lamellae structure from disassembly. Overall, this versatile postassembly process enables the tailoring of the structural features of striped colloidal ellipsoids by only using commercial BCPs and solvents.

The self-assembly of gold nanoparticles in large-pore ordered mesoporous carbons

Simple encapsulation of 3 nm gold nanoparticles in ordered mesoporous carbon with large pores of 17 nm and thick pore walls of 16 nm was achieved by a metal–ligand coordination assisted-self-assembly approach. Polystyrene-block-polyethylene-oxide (PS-b-PEO) diblock copolymer with a large molecular weight of the PS chain and mercaptopropyltrimethoxysilane were used as the template and the metal ligand, respectively. Small-angle X-ray scattering, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy showed that monodispersed aggregation-free gold nanoparticles approximately 3 nm in size were partially embedded in the large open pore structure of the ordered mesoporous carbon. The strong coordination between the gold species and the mercapto groups and the thick porous walls increased the dispersion of the gold nanoparticles and essentially inhibited particle aggregation at 600 °C. The gold nanoparticles in the ordered mesoporous carbon are active and stable in the reduction of nitroarenes involving bulky molecules using sodium borohydride as a reducing agent under ambient conditions (30 °C) in water. The large interconnected pore structure facilitates the mass transfer of bulky molecules.

Asymmetric Incorporation of Silver Nanoparticles in Polymeric Assemblies by Coassembly of Tadpole‐Like Nanoparticles and Amphiphilic Block Copolymers

A general approach to asymmetrically localize nanoparticles (NPs) in larger polymeric nanostructures is demonstrated by coassembly of tadpole-like silver NPs (AgNPs) and amphiphilic block copolymers (BCPs). The tadpole-like AgNPs are prepared by template synthesis using a tailor-made A(BC)20 star polymer, namely poly(ethylene glycol)[poly(acrylic acid)-block-polystyrene]20 [PEG(PAA-b-PS)20 ], as template resulting in AgNPs decorated with twenty short PS chains and one long PEG chain, named Ag@PEG(PS)20 . The asymmetric distribution of these AgNPs in various polymeric nanostructures, e.g., spherical micelles, cylindrical micelles, vesicles, and sponge phase, is achieved via coassembly of the as-prepared Ag@PEG(PS)20 and PEG-b-PS in solution driven by the anisotropic nature of the Ag@PEG(PS)20 . This report not only provides a new strategy for the fabrication of tadpole-like NPs but also offers opportunity for off-center distributing NPs in hybrid assemblies, which may find applications in, e.g., sensing, catalysis, and diagnostics.

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

Hierarchical Microphase Behaviors of Chiral Block Copolymers under Kinetic and Thermodynamic Control

Phase Behavior of PS-(PS-b-P2VP)3 Miktoarm Star Copolymer

We synthesized polystyrene-[polystyrene-b-poly(2-vinylpyridine)]3 miktoarm star copolymer [PSL-(PSS-b-P2VP)3], where PSL and PSS are long and short PS chains, respectively, by the combination of anionic polymerization, atom transfer radical polymerization (ATRP), and click reaction. We changed the volume fraction of the PS block (fPS) and the chain asymmetry of the PS chain τ = fPS,L/(fPS,L + fPS,S). Phase behavior of PS-(PS-b-P2VP)3 was investigated by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Inverted gyroids consisting of PS chains were formed at fPS = 0.64 and τ = 0.65, while asymmetric lamellae were observed at fPS = 0.81 and τ = 0.79. Because a long PS chain (PSL) and three short PSS-b-P2VP copolymer chains are linked at a single junction point, a huge configurational entropy penalty was expected, resulting in distorting the original phase boundaries observed for conventional AB diblock copolymer. PSS-b-P2VP chains are mainly located at the interface between PS and P2VP microdomains, whereas PSL chains fill the regions far from the interface, which causes a radial distribution to form interfacial curvature. Interestingly, the phase behavior was greatly affected by τ at a fixed fPS. For instance, at a fixed fPS (0.64), an inverted gyroid structure was formed at τ = 0.65, while a lamellar structure was observed at τ = 0.46. With the decrease in τ (or the difference of molecular weight between PSL and PSS becomes smaller), the interfacial curvature is not expected because all PSS-b-P2VP chains have no need to be arranged in the same direction. The experimental results are consistent with the predictions based on self-consistent field theory (SCFT).

(Invited) Designing Optimal Electrolytes and Interfaces in Li-S Batteries

The inter- and intra-atomic interactions of molecular species in complex electrolyte solutions affect the solvation structure and dynamical in bulk solution and at electrode/electrolyte interface. A fundamental understanding of such intricate structure-property relationships in complex solutions will allow designing optimal materials for next generation energy storage devices. A major breakthrough in battery materials is required to meet the ever-increasing proliferation of portable electronic devices, electric vehicles and their variants, as well as the need for incorporating renewable energy resources into the main energy supply [1]. In this context, lithium-sulfur (Li-S) batteries attract attention owing to their very high energy density (2,600 Wh kg-1) and specific capacity (1,675 mAh g-1) and significantly lower weight and cost, compared to lithium-ion batteries (LIBs) [2]. Fully packaged, it is expected that future Li-S batteries can operate at close to 500 Wh kg-1, which is more than twice the energy density of LIBs (200 Wh kg-1) [3]. The problem of realizing the expected high energy density is defined by several issues including the dissolution of Li-Polysulfide (PS) species into the electrolyte, insulating properties of sulfur and Li-PS species, and volume change at the cathode [4]. Overcoming these challenges requires a fundamental understanding of the interplay between events scaling over wide spatial and temporal scales, and accurate prediction of electrode and electrolyte properties to obtain design metrics for new improved materials. In this talk, I will present how we are utilizing a multi-scale-data-driven approach to gain mechanistic insight into Li-S battery by combining density functional theory (DFT) with molecular dynamics (MD) simulations. I will describe our group’s newly developed computational workflow and analysis codes for generating data with high-throughput DFT and MD simulations within the framework of the Materials Project infrastructure [5]. I will discuss usage of these tools to mitigate dissolution of LiPS species by altering the atomistic interactions between electrode and electrolyte components through functionalizing the cathode material. This approach guides and accelerates our rational selection of functional groups that exhibit strong affinity with both the cathode material and LiPS moieties from a bigger set of available candidates through fully automated DFT calculations. We use the selected candidates in detailed MD studies to understand the effect of various electrolyte variables (components, PS chain length, salt concentration) on structural and dynamical properties at the functionalized interface [6, 7]. The approach allows for creating a database of well-characterized materials to be used in machine learning-based methods as well as for testing computationally identified structures in experiments. This work provides crucial information to alleviate the dissolution of PS species during cycling, which is the main reason for rapid capacity decay in Li-S batteries.References Larcher, D. and J.-M. Tarascon, Towards greener and more sustainable batteries for electrical energy storage. Nature chemistry, 2015. 7(1): p. 19.Manthiram, A., X. Yu, and S. Wang, Lithium battery chemistries enabled by solid-state electrolytes. Nature Reviews Materials, 2017. 2(4): p. 1-16.Fang, R., et al., More reliable lithium‐sulfur batteries: status, solutions and prospects. Advanced materials, 2017. 29(48): p. 1606823.Manthiram, A., Y. Fu, and Y.-S. Su, Challenges and prospects of lithium–sulfur batteries. Accounts of chemical research, 2013. 46(5): p. 1125-1134.Jain, A., et al., Commentary: The Materials Project: A materials genome approach to accelerating materials innovation. Apl Materials, 2013. 1(1): p. 011002.Rajput, N.N., et al., Elucidating the solvation structure and dynamics of lithium polysulfides resulting from competitive salt and solvent interactions. Chemistry of Materials, 2017. 29(8): p. 3375-3379.Andersen, A., et al., Structure and dynamics of polysulfide clusters in a nonaqueous solvent mixture of 1, 3-dioxolane and 1, 2-dimethoxyethane. Chemistry of Materials, 2019. 31(7): p. 2308-2319.