Multiple Feeding Strategy for Phase Transformation of GMP in Continuous Couette–Taylor Crystallizer

A continuous Couette–Taylor (CT) crystallizer with a multiple feed mode was developed to promote the phase transformation of guanosine 5-monophosphate (GMP). In drowning-out crystallization, amorphous GMP is initially precipitated and then transformed into hydrate GMP crystals via the spontaneous nucleation of hydrate crystals and consecutive dissolution of the amorphous GMP and growth of hydrate GMP crystals. Importantly, the multiple feeding strategy had a significant accelerating effect on the phase transformation process, resulting in the complete conversion of the amorphous GMP into hydrate crystals within an overall mean residence time of 2.5 min, even with a high GMP feed concentration of 152.8 g/L and low rotation speed of 300 rpm. Thus, the phase transformation in the continuous CT crystallizer with the multiple feed mode (feeding mode IV) was at least 2 times faster than the phase transformation with the conventional feeding mode (feeding mode I), and 10 times faster when compared to the phase transformation in a continuous MSMPR crystallizer. The effectiveness of the multiple feeding mode for the phase transformation can be explained in terms of independently controlling the supersaturation, mean residence time, seeding effect, and mass transfer rates in each region of CT crystallizer depending on the multiple feeding strategy and feeding distribution ratio

Role of Nanoparticle Selectivity in the Symmetry Breaking of Cylindrically Confined Block Copolymers

We have comprehensively studied the effect of nanoparticle selectivity on the self-assembly of symmetrical block copolymer (BCP) under cylindrical confinement using simulation and experiment. For the simulation, a coarse-grained molecular dynamics (CGMD) simulation has been utilized, and we investigated the confined assembly using nanoparticles with three different interactions with block copolymer: (i) neutral to both <i>A</i> (wall-attractive) and <i>B</i> (wall-repulsive) phases, (ii) <i>B</i> domain selective, and (iii) <i>A</i> domain selective. It is predicted that nonselective (neutral) nanoparticles (NPs) tend to be placed near the interface between radially alternating layers of <i>A</i> or <i>B</i> domains, while selective (<i>A</i> or <i>B</i>) NPs swell the corresponding phase, inducing discrete asymmetrical morphologies. We also find that pure asymmetrical BCP forms more radially perforated morphologies, while symmetrical BCP/NP forms more discrete morphologies. Experimentally, we have incorporated gold or magnetite NPs with the matching three types of selectivity toward symmetrical diblock PS-<i>b</i>-PI and electrospun them. The morphologies observed from our study have been quantified by morphological classification numbers to identify the degree of asymmetry formed. The qualitative and quantitative comparisons between experiment and simulation confirm the validity of the simulation tool and shed light on the NP’s role on breaking the symmetry of BCP under cylindrical confinement

Enhanced Dispersion and Stability of Petroleum Coke Water Slurries via Triblock Copolymer and Xanthan Gum: Rheological and Adsorption Studies

The rheology of petroleum coke (petcoke) water slurries was investigated with a variety of nonionic and anionic dispersants including poly­(ethylene oxide) (PEO)-<i>b</i>-poly­(propylene oxide) (PPO)-<i>b</i>-PEO triblock copolymers (trade name: Pluronic, BASF), poly­(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), poly­(ethylene oxide) (PEO), poly­(carboxylate acid) (PCA), sodium lignosulfonate (SLS), and poly­(acrylic acid) (PAA). Each effective dispersant system shared very similar rheological behavior to the others when examined at the same volume fraction from its maximum petcoke loading. Triblock copolymer, Pluronic F127 (F127), was found to be the best dispersant by comparing the maximum petcoke loading for each dispersant. The yield stress was measured as a function of petcoke loading and dispersant concentration for F127, and a minimum dispersant concentration was observed. An adsorption isotherm and atomic force microscopy (AFM) images reveal that this effective dispersion of petcoke particles by F127 is due to the formation of a uniform monolayer of brushes where hydrophobic PPO domains of F127 adhere to the petcoke surface, while hydrophilic PEO tails fill the gap between petcoke particles. F127 was then compared to other Pluronics with various PEO and PPO chain lengths, and the effects of surface and dispersant hydrophilicity were examined. Finally, xanthan gum (XG) was tested as a stabilizer in combination with F127 for potential industrial application, and F127 appears to break the XG aggregates into smaller aggregates through competitive adsorption, leading to an excellent degree of dispersion but the reduced stability of petcoke slurries

Preparation and Characterization of Amphiphilic Triblock Terpolymer-Based Nanofibers as Antifouling Biomaterials

Antifouling surfaces are critical for the good performance of functional materials in various applications including water filtration, medical implants, and biosensors. In this study, we synthesized amphiphilic triblock terpolymers (tri-BCPs, coded as KB) and fabricated amphiphilic nanofibers by electrospinning of solutions prepared by mixing the KB with poly­(lactic acid) (PLA) polymer. The resulting fibers with amphiphilic polymer groups exhibited superior antifouling performance to the fibers without such groups. The adsorption of bovine serum albumin (BSA) on the amphiphilic fibers was about 10-fold less than that on the control surfaces from PLA and PET fibers. With the increase of the KB content in the amphiphilic fibers, the resistance to adsorption of BSA was increased. BSA was released more easily from the surface of the amphiphilic fibers than from the surface of hydrophobic PLA or PET fibers. We have also investigated the structural conformation of KB in fibers before and after annealing by contact angle measurements, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and coarse-grained molecular dynamics (CGMD) simulation to probe the effect of amphiphilic chain conformation on antifouling. The results reveal that the amphiphilic KB was evenly distributed within as-spun hybrid fibers, while migrated toward the core from the fiber surface during thermal treatment, leading to the reduction in antifouling. This suggests that the antifouling effect of the amphiphilic fibers is greatly influenced by the arrangement of amphiphilic groups in the fibers

Harvesting Interconductivity and Intraconductivity of Graphene Nanoribbons for a Directly Deposited, High-Rate Silicon-Based Anode for Li-Ion Batteries

Batteries for high-rate applications such as electric vehicles need to be efficient at mobilizing charges (both electrons and ions). To this end, choice of the conductive carbon in the electrode can make a significant difference in the performance of the electrode. In this work, graphene nanoribbons (GNRs) are explored as conductive pathways for a silicon-based anode. Water-based electrospinning is employed to directly deposit poly­(vinyl alcohol) (PVA)–silicon–graphene nanoribbon composite fibers on a copper current collector. The size of the employed GNRs dictates their placement: either inside each fiber (small GNRs) or as a bridge between multiple fibers (large GNRs). Galvanostatic charge/discharge cycles reveal that fibers with GNRs have higher capacity and overall retention compared to those with corresponding precursor carbon nanotubes (CNTs). To further distinguish the effectiveness of GNRs as the conductive agent, samples with two GNRs and their parent CNTs were subject to rate-capability tests. Fibers with large GNR inclusions exhibit an excellent performance at fast rates (1400 mAh g^–1 at 12.6 A g^–1). For both pairs, enhancement in the performance of GNRs over CNTs grows with increasing rates. Finally, a small amount of large GNRs (1 wt %) is blended with small GNRs in the fibers to create synergy between intra- and interconductivity provided by small and large GNRs, respectively. The resulting fiber mat exhibits the same capacity as that of only small GNRs, even at a current rate that is 4 times higher (300 mAh g^–1 at 21 A g^–1)

Zwitterionic Polymer Gradient Interphases for Reversible Zinc Electrochemistry in Aqueous Alkaline Electrolytes

Aqueous alkaline zinc batteries are of scientific and technological interest because of the potential they offer for cost-effective and safe storage of electrical energy. Poor electrochemical reversibility and shape change of the Zn anode, propensity of Zn to become passivated by surface oxides and hydroxide films upon prolonged exposure to the electrolyte, and electroreduction of water are well-studied but remain unsolved challenges. Here, we create and study electrochemical and transport properties of precise, spatially tunable zwitterionic polymer interphases grown directly on Zn using an initiated-chemical vapor deposition polymerization methodology. In aqueous alkaline media, spatial gradients in compositionfrom the polymer–electrolyte interface to the solid–polymer interfacepromote highly reversible redox reactions at high current density (20 mA cm–2) and high areal capacity (10 mAh cm–2). Via molecular dynamics and experimental analyses, we conclude that the interphases function by regulating the distribution and activity of interfacial water molecules, which simultaneously enables fast ion transport and suppression of surface passivation and the hydrogen evolution reaction. To illustrate the practical relevance of our findings, we study aqueous Zn||NiOOH and Zn||air batteries and observe that zwitterionic polymer interphases produce extended life at high currents and high areal capacity

Adaptive Ion Channels Formed in Ultrathin and Semicrystalline Polymer Interphases for Stable Aqueous Batteries

Aqueous Zn batteries have recently emerged as promising candidates for large-scale energy storage, driven by the need for a safe and cost-effective technology with sufficient energy density and readily accessible electrode materials. However, the energy density and cycle life of Zn batteries have been limited by inherent chemical, morphological, and mechanical instabilities at the electrode–electrolyte interface where uncontrolled reactions occur. To suppress the uncontrolled reactions, we designed a crystalline polymer interphase for both electrodes, which simultaneously promotes electrode reversibility via fast and selective Zn transport through the adaptive formation of ion channels. The interphase comprises an ultrathin layer of crystalline poly(1H,1H,2H,2H-perfluorodecyl acrylate), synthesized and applied as a conformal coating in a single step using initiated chemical vapor deposition (iCVD). Crystallinity is optimized to improve interphase stability and Zn-ion transport. The optimized interphase enables a cycle life of 9500 for Zn symmetric cells and over 11,000 for Zn-MnO2 full-cell batteries. We further demonstrate the generalizability of this interphase design using Cu and Li as examples, improving their stability and achieving reversible cycling in both. The iCVD method and molecular design unlock the potential of highly reversible and cost-effective aqueous batteries using earth-abundant Zn anode materials, pointing to grid-scale energy storage