Addition Of Small Molecules Research Articles

Tuning Self-Healing Property of Stiff Supramolecular Polymer for Flexible Electronics

Organic electronics are receiving increasing attention for the development of flexible devices, due to the generally easier processability and higher flexibility of organic, compared to inorganic, materials. However, although many suitable organic materials possess some measure of elasticity, flexible electronic devices are often prone to cracking or breaking over time, resulting in poor durability and reliability. As a result, the burgeoning field of self-healing materials for electrochemical devices has begun to attract attention. Self-healing polymers can be designed to recover their original mechanical properties after physical damage, increasing their useful lifetime. Therefore, development of self-healing polymers is highly desirable to accommodate increasing demand for flexible devices. For decades, soft gels, elastomers, and hybrid organic-inorganic systems with self-healing properties have been designed based on reversible interactions and dynamic covalent bonds. However, previous approaches typically sacrifice stiffness to achieve self-healing properties, mostly resulting in materials with tensile moduli less than 1 MPa. These soft and deformable materials are less likely to maintain reliable and stable pathways for electron or ion movement in devices. Additionally, considering different application conditions, how to modulate these self-healing and mechanical properties in response to various environment cues, such as temperature, pH, or light is vital for improving long-term mechanical integrity as well. In particularly, tunability based on temperature is widely useful for initiating self-healing ability and controlling stiffness for flexible electronics, which will widen their ultimate potential applications. Herein, we report a supramolecular polymer system based on pi-pi interaction between naphthalenediimide (NDI) and pyrene (Py) derivatives, which possesses high stiffness (Young’s modulus > 69 MPa) while also retaining mild self-healing temperature (< 50oC) and inherent ionic conductivity (> 10-6 S/cm at 50°C when doped with LiTFSI). Additionally, we demonstrate the tunability of the pi-pi interaction modes by doping small molecule additives into the polymer, which can modulate the interaction strength and crosslinking density in the system. The self-healing temperature and Young’s modulus are tunable in a wide range (30-60oC, 69-219 MPa) to satisfy different potential applications, such as artificial skin and wearable batteries. We demonstrate our polymer possesses decent stretchability (100% strain without cracking), flexibility, and ability to heal cracking at human body temperature, which shows application potential for wearable electronics. Compared to softer self-healing polymers reported previously, our system not only transcends the currently-available regime of mechanical properties in self-healing systems, but also provides a general strategy for tuning self-healing and mechanical properties in supramolecular polymers.

Haploid embryonic stem cells can be enriched and maintained by simple filtration

Mammalian haploid embryonic stem cells (haESCs) serve as a powerful tool for genetic analyses at both the cellular and organismal levels. However, spontaneous diploidization of haESCs limits their use in these analyses. Addition of small molecules to the culture medium to control the cell cycle can slow down diploidization, but cell-sorting methods such as FACS are still required to enrich haploid cells for long-term maintenance in vitro Here, acting on our observation that haploid and diploidized cells differ in diameter, we developed a simplified filtration method to enrich haploid cells from cultured haESCs. We found that regular cell filtration with this system reliably maintained the haploidy of mouse haESCs for over 30 passages. Importantly, CRISPR/Cas9-mediated knockout and knockin were successfully achieved in the filtered cells, leading to stable haploid cell lines carrying the desired gene modifications. Of note, by injecting haESCs into metaphase II oocytes, we efficiently obtained live mice with the expected genetic traits, indicating that regular filtration maintained the functional integrity of haESCs. Moreover, this filtration system was also feasible for derivation of mouse haESCs from parthenogenetic haploid blastocysts and for human haESC maintenance. In conclusion, we have identified a reliable, efficient, and easy-to-handle technique for countering diploidization of haploid cells, a major obstacle in haESC applications.

Effect of heavy atoms on photochemically induced dynamic nuclear polarization in liquids

Given its short hyperpolarization time (∼10−6 s) and mostly non-perturbative nature, photo-chemically induced dynamic nuclear polarization (photo-CIDNP) is a powerful tool for sensitivity enhancement in nuclear magnetic resonance. In this study, we explore the extent of 1H-detected 13C nuclear hyperpolarization that can be gained via photo-CIDNP in the presence of small-molecule additives containing a heavy atom. The underlying rationale for this methodology is the well-known external-heavy-atom (EHA) effect, which leads to significant enhancements in the intersystem-crossing rate of selected photosensitizer dyes from photoexcited singlet to triplet. We exploited the EHA effect upon addition of moderate amounts of halogen-atom-containing cosolutes. The resulting increase in the transient triplet-state population of the photo-CIDNP sensitizer fluorescein resulted in a significant increase in the nuclear hyperpolarization achievable via photo-CIDNP in liquids. We also explored the internal-heavy-atom (IHA) effect, which is mediated by halogen atoms covalently incorporated into the photosensitizer dye. Widely different outcomes were achieved in the case of EHA and IHA, with EHA being largely preferable in terms of net hyperpolarization.

More than One Way to Skin a Catalyst

In this issue of Cell Chemical Biology, Diaz etal. (2017) report a strategy to achieve temporal, spatial, and stoichiometric control over the protein kinase cAbl in living cells. They achieve this by splitting cAbl into two inactive fragments that form an active kinase upon small molecule addition, potentially providing a general way to probe the wiring of signal transduction networks.

Conservative Exposure Predictions for Rapid Risk Assessment of Phase-Separated Additives in Medical Device Polymers

A novel approach for rapid risk assessment of targeted leachables in medical device polymers is proposed and validated. Risk evaluation involves understanding the potential of these additives to migrate out of the polymer, and comparing their exposure to a toxicological threshold value. In this study, we propose that a simple diffusive transport model can be used to provide conservative exposure estimates for phase separated color additives in device polymers. This model has been illustrated using a representative phthalocyanine color additive (manganese phthalocyanine, MnPC) and polymer (PEBAX 2533) system. Sorption experiments of MnPC into PEBAX were conducted in order to experimentally determine the diffusion coefficient, D=(1.6±0.5)×10-11cm2/s, and matrix solubility limit, C s=0.089wt.%, and model predicted exposure values were validated by extraction experiments. Exposure values for the color additive were compared to a toxicological threshold for a sample risk assessment. Results from this study indicate that a diffusion model-based approach to predict exposure has considerable potential for use as a rapid, screening-level tool to assess the risk of color additives and other small molecule additives in medical device polymers.

Melt Extrusion of High-Dose Co-Amorphous Drug-Drug Combinations : Theme: Formulation and Manufacturing of Solid Dosage Forms Guest Editors: Tony Zhou and Tonglei Li.

Many future drug products will be based on innovative manufacturing solutions, which will increase the need for a thorough understanding of the interplay between drug material properties and processability. In this study, hot melt extrusion of a drug-drug mixture with minimal amount of polymeric excipient was investigated. Using indomethacin-cimetidine as a model drug-drug system, processability of physical mixtures with and without 5% (w/w) of polyethylene oxide (PEO) were studied using Differential Scanning Calorimetry (DSC) and Small Amplitude Oscillatory Shear (SAOS) rheometry. Extrudates containing a co-amorphous glass solution were produced and the solid-state composition of these was studied with DSC. Rheological analysis indicated that the studied systems display viscosities higher than expected for small molecule melts and addition of PEO decreased the viscosity of the melt. Extrudates of indomethacin-cimetidine alone displayed amorphous-amorphous phase separation after 4weeks of storage, whereas no phase separation was observed during the 16week storage of the indomethacin-cimetidine extrudates containing 5% (w/w) PEO. Melt extrusion of co-amorphous extrudates with low amounts of polymer was found to be a feasible manufacturing technique. Addition of 5% (w/w) polymer reduced melt viscosity and prevented phase separation.

(Invited) Characterisation of Metal Deposition and Metal Dissolution Processes in Deep Eutectic Solvents Using Electrochemical, Gravimetric and Neutron Scattering Methods

Electrolytic coatings of metals such as nickel, chromium, zinc, silver and gold are commonly applied as decorative and/or functional coatings. Some of the functional benefits which metal coatings provide are corrosion resistance, wear resistance, electrocatalysis and use in magnetic applications. A range of strategic manufacturing industries are dependent on such electrolytic coatings including electronics, aerospace, automotive and energy. The vast majority of electrolytic coatings are plated from aqueous solutions but stringent health and safety legislation governing transport, use and disposal of feedstock chemicals has driven the challenge for innovation in electrolyte technology that facilitates coatings from less toxic materials and in a manner that is more efficient and more consistent with environmental and process sustainability. We have been motivated by this challenge and have developed a range of novel solvent systems for deposition of metal coatings as alternatives to existing process (e.g. Ni, Zn, Cu, Ag, Ag) as well as novel electrolytes for deposition of reactive metals such as Al. These electrolytes have become known as Deep Eutectic Solvents and have shown utility and promise in a range of metal finishing processes. [1] Whilst the thermodynamics, kinetics, metal ion speciation and growth processes of electrolytic coatings from aqueous solutions have been studied for more than one hundred years, little is currently known about these fundamental aspects of electrochemical deposition from DES media. [2] Here we describe our studies into the electrochemical characterisation of a range of metals in DES electrolytes. In particular, we will focus on aspects of growth and dissolution processes and how these effect the morphology and composition of metal films. We will describe the characterisation of thin metal films in DES media using a range of time resolved techniques including cyclic voltammetry, chronopotentiometry, chronoampertometry, gravimetry (QCM), neutron reflectometry (NR) and surface metrology. The use of in-situ electrochemical NR methods is novel and we will present new data on the growth and dissolution of single metal and bi-layer metals films. The Figure shows time resolved NR data for the electrochemical dissolution of a Cu/Ag bi-layer on a Au substrate. We will also present complimentary data on the characterisation of the same systems using so-called Simultaneous Thickness Electrochemical Potential (STEP) chronopotentiometric methods. We will consider the effect of small-molecule additives on surface morphology and finish (roughness) of electrolytic coatings. [3] Organic and inorganic additives are often added to electroplating solutions to improve surface finish, reduce roughness and promote uniform surface morphology of the coatings. Such additives are usually small molecules and often referred to as brighteners or levellers. However, there have been limited investigations into the effect of such additives on electrodeposition from ionic liquids (ILs) and deep eutectic solvents (DESs). Here we will describe the effect of four additives on electrolytic plating of exemplar metals, nickel and zinc, from an ethyleneglycol based DES; these are nicotinic acid (NA), methylnicotinate (MN), 5,5-dimethyl- hydantoin (DMH) and boric acid (BA). The additives show limited influence on the bulk speciation but have significant influence on the electrochemical behaviour of metal deposition. Small concentrations (ca. 15 mM) of NA and MN show inhibition of metal ion reduction whereas high concentrations of DMH and BA are required for a modest difference in behaviour from the additive free system. NA and MN also show that they significantly alter the nucleation and growth mechanism when compared to the additive free system and those with DMH and BA. Each of the additive systems had the effect of producing brighter and flatter bulk electrodeposits and with increased coating hardness. “Deep Eutectic Solvents (DESs) and their Applications”, Emma L. Smith, Karl S. Ryder and Andrew P. Abbott, Chem. Rev., 2014, 114, 11060.“EXAFS Study into the Speciation of Metal Salts Dissolved in Ionic Liquids and Deep Eutectic Solvents”, Jennifer M. Hartley, Chung-Man Ip, Gregory C.H. Forrest, Kuldip Singh, Stephen J. Gurman, Karl S. Ryder, Andrew P. Abbott and Gero Frisch, Inorg. Chem., 2014, 53(12), 6280.“Bright Metal Coatings from Sustainable Electrolytes: The Effect of Molecular Additives on Electrodeposition of Nickel from a Deep Eutectic Solvent”, Andrew P. Abbott, Andrew Ballantyne, Robert C. Harris, Jamil A. Juma and Karl S. Ryder, Phys. Chem. Chem. Phys., 2017, 19. 3219. Figure 1

Efficient Generation of Dopamine Neurons by Synthetic Transcription Factor mRNAs

Generation of functional dopamine (DA) neurons is an essential step for the development of effective cell therapy for Parkinson's disease (PD). The generation of DA neurons can be accomplished by overexpression of DA-inducible genes using virus- or DNA-based gene delivery methods. However, these gene delivery methods often cause chromosomal anomalies. In contrast, mRNA-based gene delivery avoids this problem and therefore is considered safe to use in the development of cell-based therapy. Thus, we used mRNA-based gene delivery method to generate safe DA neurons. In this study, we generated transformation-free DA neurons by transfection of mRNA encoding DA-inducible genes Nurr1 and FoxA2. The delivery of mRNA encoding dopaminergic fate inducing genes proved sufficient to induce naive rat forebrain precursor cells to differentiate into neurons exhibiting the biochemical, electrophysiological, and functional properties of DA neurons invitro. Additionally, the generation efficiency of DA neurons was improved by the addition of small molecules, db-cAMP, and the adjustment of transfection timing. The successful generation of DA neurons using an mRNA-based method offers the possibility of developing clinical-grade cell sources for neuronal cell replacement treatment for PD.

Tuning Biocompatible Block Copolymer Micelles by Varying Solvent Composition: Dynamics and Populations of Micelles and Unimers

Optimization of micellar molecular encapsulation systems, such as drug delivery vehicles, can be achieved through fundamental understanding of block copolymer micelle structure and dynamics. Herein, we present a study of PEO–PCL block copolymer spherical micelles that self-assemble at 1% wt/vol in D2O–THF-d8 mixtures. Varying solvent composition as a function of cosolvent THF-d8 at constant polymer concentration (1% wt/vol) allows sensitive study of how small molecule additives influence micelle structure and dynamics. We conduct nuclear magnetic resonance spectroscopy and diffusometry on two block copolymer (2k series: PEO2k–PCL3k; 5k series: PEO5k–PCL8k) spherical micelles that show drastically different behaviors. Unimers and micelles coexist in solution from 10–60 vol % THF-d8 for the 2k series but only coexist at 60 vol % THF-d8 for the 5k series. At ≥ 60 vol % THF-d8 micelles disassemble into free unimers for both series. We observe relatively flat micelle diffusion coefficients (∼1 × 10–10 m2/s) wi...

Polymer/Small Molecule/Fullerene Based Ternary Solar Cells

Polymer/small molecule/fullerene based ternary solar cells have made great progress and have attracted considerable attention in recent years. The addition of small molecules can effectively compensate for the disadvantages of polymer solar cells, such as increasing the light‐harvesting ability, providing cascade energy levels, and tuning the morphology. Thus, polymer/small molecule/fullerene based ternary solar cells are promising candidates to obtain further improvements in photovoltaic performance for organic solar cells. This article summarizes the developments of ternary solar cells with small molecules as third components, and represents the possible photo‐physics process in the ternary blends. In addition, the challenges and perspectives for ternary solar cells are discussed.

Light-controlled gene expression in yeast using photocaged Cu2+

The manipulation of cellular function, such as the regulation of gene expression, is of great interest to many biotechnological applications and often achieved by the addition of small effector molecules. By combining effector molecules with photolabile protecting groups that mask their biological activity until they are activated by light, precise, yet minimally invasive, photocontrol is enabled. However, applications of this trendsetting technology are limited by the small number of established caged compound-based expression systems. Supported by computational chemistry, we used the versatile photolabile chelator DMNP-EDTA, long-established in neurobiology for photolytic Ca2+ release, to control Cu2+ release upon specific UV-A irradiation. This permits light-mediated control over the widely used Cu2+-inducible pCUP1 promoter from S. cerevisiae and thus constitutes the first example of a caged metal ion to regulate recombinant gene expression. We screened our novel DMNP-EDTA-Cu system for best induction time and expression level of eYFP with a high-throughput online monitoring system equipped with an LED array for individual illumination of every single well. Thereby, we realized a minimally invasive, easy-to-control, parallel and automated optical expression regulation via caged Cu2+ allowing temporal and quantitative control as a beneficial alternative to conventional induction via pipetting CuCl2 as effector molecule.

The immunoproteasome is induced by cytokines and regulates apoptosis in human islets.

In addition to degrading misfolded and damaged proteins, the proteasome regulates the fate of cells in response to stress. The role of the proteasome in pro-inflammatory cytokine-induced human beta-cell apoptosis is unknown. Using INS-1, INS-1E and human islets exposed to combinations of IFNγ, IL-1β and TNFα with or without addition of small molecules, we assessed the role of the immunoproteasome in pancreatic beta-cell demise. Here, we show that cytokines induce the expression and activity of the immuno-proteasome in INS-1E cells and human islets. Cytokine-induced expression of immuno-proteasome subunits, but not activity, depended upon histone deacetylase 3 activation. Inhibition of JAK1/STAT1 signaling did not affect proteasomal activity. Inhibition of the immuno-proteasome subunit PSMB8 aggravated cytokine-induced human beta-cell apoptosis while reducing intracellular levels of oxidized proteins in INS-1 cells. While cytokines increased total cellular NFκB subunit P50 and P52 levels and reduced the cytosolic NFκB subunit P65 and IκB levels, these effects were unaffected by PSMB8 inhibition. We conclude that beta cells upregulate immuno-proteasome expression and activity in response to IFNγ, likely as a protective response to confine inflammatory signaling.

Aged Tris(trimethylsilyl) Phosphite (TMSPi) As a L.I.B. Electrolyte Additive

The use of electrolyte additives has been and continues to be an economical and effective approach to enhance the performance and increase the lifetime of lithium ion battery systems. In the presence of additives, the baseline performance of electrolytes can be improved due to the formation of surface films on the electrodes, HF scavenging in the bulk electrolyte, etc. However, the interaction between electrolytes and small molecule additives are rarely studied due to the assumed inertness of the system. While this inert relationship may hold true for many additives, we have found that one commonly used additive, tris(trimethylsilyl) phosphite (TMSPi), demonstrates a dynamic (reactive) relationship when used with a LiPF6-based electrolyte (1.2 M LiPF6 in EC/EMC, 3/7 wt/wt). Our findings suggest that immediately after the addition of TMSPi into the electrolyte, the nature of the electrolyte changes and the properties of the bulk electrolyte are drastically different between immediately making the solution and waiting less than a week. We present electrochemical data comparing freshly prepared (same day) and “aged” (one week) TMSPi-based electrolyte formulations. Our results indicate that the effect of electrolyte aging on cell electrochemistry (LiNi0.5Mn0.3Co0.2O2 /graphite full cells operating between 3.0-4.4 V) can be dramatic with observable differences in impedance, redox behavior, surface film formation and transition metal dissolution from the positive electrode. The data presented sheds considerable light on the possible interactions between additives and electrolyte and are of utmost importance when considering electrolyte formulations for lithium ion batteries.

Trap Healing for High-Performance Low-Voltage Polymer Transistors and Solution-Based Analog Amplifiers on Foil.

Solution-processed semiconductors such as conjugated polymers have great potential in large-area electronics. While extremely appealing due to their low-temperature and high-throughput deposition methods, their integration in high-performance circuits has been difficult. An important remaining challenge is the achievement of low-voltage circuit operation. The present study focuses on state-of-the-art polymer thin-film transistors based on poly(indacenodithiophene-benzothiadiazole) and shows that the general paradigm for low-voltage operation via an enhanced gate-to-channel capacitive coupling is unable to deliver high-performance device behavior. The order-of-magnitude longitudinal-field reduction demanded by low-voltage operation plays a fundamental role, enabling bulk trapping and leading to compromised contact properties. A trap-reduction technique based on small molecule additives, however, is capable of overcoming this effect, allowing low-voltage high-mobility operation. This approach is readily applicable to low-voltage circuit integration, as this work exemplifies by demonstrating high-performance analog differential amplifiers operating at a battery-compatible power supply voltage of 5 V with power dissipation of 11 µW, and attaining a voltage gain above 60 dB at a power supply voltage below 8 V. These findings constitute an important milestone in realizing low-voltage polymer transistors for solution-based analog electronics that meets performance and power-dissipation requirements for a range of battery-powered smart-sensing applications.

Enhancing Drug Efficacy and Therapeutic Index through Cheminformatics-Based Selection of Small Molecule Binary Weapons That Improve Transporter-Mediated Targeting: A Cytotoxicity System Based on Gemcitabine.

The transport of drug molecules is mainly determined by the distribution of influx and efflux transporters for which they are substrates. To enable tissue targeting, we sought to develop the idea that we might affect the transporter-mediated disposition of small-molecule drugs via the addition of a second small molecule that of itself had no inhibitory pharmacological effect but that influenced the expression of transporters for the primary drug. We refer to this as a “binary weapon” strategy. The experimental system tested the ability of a molecule that on its own had no cytotoxic effect to increase the toxicity of the nucleoside analog gemcitabine to Panc1 pancreatic cancer cells. An initial phenotypic screen of a 500-member polar drug (fragment) library yielded three “hits.” The structures of 20 of the other 2,000 members of this library suite had a Tanimoto similarity greater than 0.7 to those of the initial hits, and each was itself a hit (the cheminformatics thus providing for a massive enrichment). We chose the top six representatives for further study. They fell into three clusters whose members bore reasonable structural similarities to each other (two were in fact isomers), lending strength to the self-consistency of both our conceptual and experimental strategies. Existing literature had suggested that indole-3-carbinol might play a similar role to that of our fragments, but in our hands it was without effect; nor was it structurally similar to any of our hits. As there was no evidence that the fragments could affect toxicity directly, we looked for effects on transporter transcript levels. In our hands, only the ENT1-3 uptake and ABCC2,3,4,5, and 10 efflux transporters displayed measurable transcripts in Panc1 cultures, along with a ribonucleoside reductase RRM1 known to affect gemcitabine toxicity. Very strikingly, the addition of gemcitabine alone increased the expression of the transcript for ABCC2 (MRP2) by more than 12-fold, and that of RRM1 by more than fourfold, and each of the fragment “hits” served to reverse this. However, an inhibitor of ABCC2 was without significant effect, implying that RRM1 was possibly the more significant player. These effects were somewhat selective for Panc cells. It seems, therefore, that while the effects we measured were here mediated more by efflux than influx transporters, and potentially by other means, the binary weapon idea is hereby fully confirmed: it is indeed possible to find molecules that manipulate the expression of transporters that are involved in the bioactivity of a pharmaceutical drug. This opens up an entirely new area, that of chemical genomics-based drug targeting.

Improved Post-Thaw Function and Epigenetic Changes in Mesenchymal Stromal Cells Cryopreserved Using Multicomponent Osmolyte Solutions.

Current methods for freezing mesenchymal stromal cells (MSCs) result in poor post-thaw function, which limits the clinical utility of these cells. This investigation develops a novel approach to preserve MSCs using combinations of sugars, sugar alcohols, and small-molecule additives. MSCs frozen using these solutions exhibit improved post-thaw attachment and a more normal alignment of the actin cytoskeleton compared to cells exposed to dimethylsulfoxide (DMSO). Osteogenic and chondrogenic differentiation assays show that cells retain their mesenchymal lineage properties. Genomic analysis indicates that the different freezing media evaluated have different effects on the levels of DNA hydroxymethylation, which are a principal epigenetic mark and a key step in the demethylation of CpG doublets. RNA sequencing and quantitative real time-polymerase chain reaction validation demonstrate that transcripts for distinct classes of cytoprotective genes, as well as genes related to extracellular matrix structure and growth factor/receptor signaling are upregulated in experimental freezing solutions compared to DMSO. For example, the osmotic regulator galanin, the antiapoptotic marker B cell lymphoma 2, as well as the cell surface adhesion molecules CD106 (vascular cell adhesion molecule 1) and CD54 (intracellular adhesion molecule 1) are all elevated in DMSO-free solutions. These studies validate the concept that DMSO-free solutions improve post-thaw biological functions and are viable alternatives for freezing MSCs. These novel solutions promote expression of cytoprotective genes, modulate the CpG epigenome, and retain the differentiation ability of MSCs, suggesting that osmolyte-based freezing solutions may provide a new paradigm for therapeutic cell preservation.

Seeing red; the development of pON.mCherry, a broad-host range constitutive expression plasmid for Gram-negative bacteria.

The development of plasmid-mediated gene expression control in bacteria revolutionized the field of bacteriology. Many of these expression control systems rely on the addition of small molecules, generally metabolites or non-metabolized analogs thereof, to the growth medium to induce expression of the genes of interest. The paradigmatic example of an expression control system is the lac system from Escherichia coli, which typically relies on the Ptac promoter and the Lac repressor, LacI. In many cases, however, constitutive gene expression is desired, and other experimental approaches require the coordinated control of multiple genes. While multiple systems have been developed for use in E. coli and its close relatives, the utility and/or functionality of these tools does not always translate to other species. For example, for the Gram-negative pathogen, Legionella pneumophila, a causative agent of Legionnaires’ Disease, the aforementioned Ptac system represents the only well-established expression control system. In order to enhance the tools available to study bacterial gene expression in L. pneumophila, we developed a plasmid, pON.mCherry, which confers constitutive gene expression from a mutagenized LacI binding site. We demonstrate that pON.mCherry neither interferes with other plasmids harboring an intact LacI-Ptac expression system nor alters the growth of Legionella species during intracellular growth. Furthermore, the broad-host range plasmid backbone of pON.mCherry allows constitutive gene expression in a wide variety of Gram-negative bacterial species, making pON.mCherry a useful tool for the greater research community.

Hierarchical Self-Assembly of Halogen-Bonded Block Copolymer Complexes into Upright Cylindrical Domains

SummarySelf-assembly of block copolymers into well-defined, ordered arrangements of chemically distinct domains is a reliable strategy for preparing tailored nanostructures. Microphase separation results from the system, minimizing repulsive interactions between dissimilar blocks and maximizing attractive interactions between similar blocks. Supramolecular methods have also achieved this separation by introducing small-molecule additives binding specifically to one block by noncovalent interactions. Here, we use halogen bonding as a supramolecular tool that directs the hierarchical self-assembly of low-molecular-weight perfluorinated molecules and diblock copolymers. Microphase separation results in a lamellar-within-cylindrical arrangement and promotes upright cylindrical alignment in films upon rapid casting and without further annealing. Such cylindrical domains with internal lamellar self-assemblies can be cleaved by solvent treatment of bulk films, resulting in separated and segmented cylindrical micelles stabilized by halogen-bond-based supramolecular crosslinks. These features, alongside the reversible nature of halogen bonding, provide a robust modular approach for nanofabrication.

How and Why Polymer Glasses Lose Their Ductility Due to Plasticizers

Tensile extension tests have been carried out to examine mechanical responses of polymer glasses under the influence of small molecule additives that plasticize the polymers by lowering their glass transition temperatures Tg and speeding up their α relaxation times. It is shown that incorporation of 4% triphenyl phosphate (TPP) into poly(methyl methacrylate) turns a brittle PMMA at 70 °C into a ductile glass, capable of significant cold drawing, as expected according to the conventional wisdom. However, despite the evidence that the same TPP also reduces polystyrene’s Tg and increases the segmental mobility, the ductile PS turns brittle at 70 °C upon addition of 4% TPP at the same low drawing speed. This counterintuitive behavior is also found in the pair of TPP and poly(styrene–acrylonitrile). Thus, the present observations require us to incorporate new ingredients into the classical Eyring-type interpretation of plastic flow in a glassy polymer.

Fabrication of convex lens-shaped polymer particles by tuning the interfacial interaction

With the addition of small molecules to emulsion droplets containing block copolymers, anisotropic convex lens-like particles with hexagonally stacked cylindrical domains can be readily achieved by using a single surfactant to create a neutral interface for both blocks.