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Different projections of hexagonal structures of QPDMAEMA-b-POEGMA/DNA complexes CR = 10 with a spacing of 3 nm, as shown in FFTs.

Temperature control of rheological properties of aqueous solutions can be achieved by the addition of amphiphilic polymers that show temperature-dependent self-assembly. For this purpose, we explored three sets of acrylamide-based block copolymers with BAB*-, B2AB*-, and B(AB*)2-type architectures, where “B” represents a permanently hydrophobic unit, “A” is a permanently hydrophilic block, and “B*” is a thermoswitchable block, which undergoes a phase transition of the lower critical solution temperature (LCST) type. Depending on the specific polymer architecture and choice of the thermoresponsive block, the viscosity of their aqueous solutions can augment substantially with increasing temperature. The macroscopic rheological changes were correlated with the results of static and dynamic light scattering (SLS, DLS) and small-angle neutron scattering (SANS) experiments, showing a clear correlation with the mesoscopic organization of the respective systems. Complementary studies with the fluorescence probe Prodan also revealed a clear correlation of the enhanced viscosity to the formation of hydrophobic domains of the thermoresponsive block. Accordingly, the appropriate design of such “smart” copolymer thickeners enables the tuning of the viscoelastic properties of aqueous solutions.

Carbon nanotubes (CNTs) are stiff, all-carbon macromolecules with diameters as small as one nanometer and few microns long. Solutions of CNTs in chlorosulfonic acid (CSA) follow the phase behavior of rigid rod polymers interacting via a repulsive potential and display a liquid crystalline phase at sufficiently high concentration. Here, we show that small-angle X-ray scattering and polarized light microscopy data can be combined to characterize quantitatively the morphology of liquid crystalline phases formed in CNT solutions at concentrations from 3 to 6.5 % by volume. We find that upon increasing their concentration, CNTs self-assemble into a liquid crystalline phase with a pleated texture and with a large inter-particle spacing that could be indicative of a transition to higher-order liquid crystalline phases. We explain how thermal undulations of CNTs can enhance their electrostatic repulsion and increase their effective diameter by an order of magnitude. By calculating the critical concentration, where the mean amplitude of undulation of an unconstrained rod becomes comparable to the rod spacing, we find that thermal undulations start to affect steric forces at concentrations as low as the isotropic cloud point in CNT solutions.

The synthesis of defined triphilic terpolymers with hydrophilic, lyophilic, and fluorophilic blocks is an important challenge as a basis for the development of multicompartment self-assembled structures with potential for, e.g., cascade catalysis and multidrug loading. The synthesis of fluorophilic poly(2-oxazoline)s generally suffers from a very low reactivity of fluorinated 2-oxazoline monomers in cationic ring-opening polymerization (CROP). We report a systematic study on overcoming the extremely low reactivity of 2-perfluoroalkyl-2-oxazolines in CROP by the insertion of methyl and ethyl hydrocarbon spacers between the 2-oxazoline ring and the trifluoromethyl group. The kinetic studies showed the gradual increase of the rate of polymerization with increasing of the hydrocarbon spacer length. The monomer with an ethyl spacer was found to have similar reactivity as 2-alkyl-2-oxazolines and allowed the synthesis of defined triphilic triblock copolymers.

Conspectus Cryogenic-temperature transmission electron microscopy (cryo-TEM) of aqueous systems has become a widely used methodology, especially in the study of biological systems and synthetic aqueous systems, such as amphiphile and polymer solutions. Cryogenic-temperature scanning electron microscopy (cryo-SEM), while not as widely used as cryo-TEM, is also found in many laboratories of basic and applied research. The application of these methodologies, referred to collectively as cryogenic-temperature electron microscopy (cryo-EM) for direct nanostructural studies of nonaqueous liquid systems is much more limited, although such systems are important in basic research and are found in a very large spectrum of commercial applications. The study of nonaqueous liquid systems by cryo-EM poses many technical challenges. Specimen preparation under controlled conditions of air saturation around the specimen cannot be performed by the currently available commercial system, and the most effective cryogen, freezing ethane, cannot be used for most such liquid systems. Imaging is often complicated by low micrograph contrast and high sensitivity of the specimens to the electron beam. At the beginning of this Account, we describe the basic principles of cryo-EM, emphasizing factors that are essential for successful direct imaging by cryo-TEM and cryo-SEM. We discuss the peculiarities of nonaqueous liquid nanostructured systems when studied with these methodologies and how the technical difficulties in imaging nonaqueous systems, from oil-based to strong acid-based liquids, have been overcome, and the applicability of cryo-TEM and cryo-SEM has been expanded in recent years. Modern cryo-EM has been advanced by a number of instrumental developments, which we describe. In the TEM, these include improved electron field emission guns (FEGs) and microscope optics, the Volta phase plate to enhance image contrast by converting phase differences to amplitude differences without the loss of resolution by an objective lens strong underfocus, and highly sensitive image cameras that allow the recording of TEM images with minimal electron exposure. In the SEM, we take advantage of improved FEGs that allow imaging at a low (around 1 kV) electron acceleration voltage that is essential for high-resolution imaging and for avoiding specimen charging of uncoated nonconductive specimens, better optics, and a variety of sensitive detectors that have considerably improved resolution and, under the proper conditions, give excellent contrast even between elements quite close on the periodic table of the elements, such as the most important oxygen and carbon atoms. Finally we present and analyze several examples from our recent studies, which illustrate the issues presented above, including the remarkable progress made in recent years in this field and the strength and applicability of cryo-EM methodologies.

The delivery of therapeutics into sites of action by using cargo-delivery platforms potentially minimizes their premature degradation and fast clearance from the bloodstream. Additionally, drug-loaded stimuli-responsive supramolecular assemblies can be produced to respond to the inherent features of tumor microenvironments, such as extracellular acidosis. We report in this framework the use of pH-responsive polymersomes (PSs) manufactured using poly([N-(2-hydroxypropyl)] methacrylamide)35-b-poly[2-(diisopropylamino)ethyl methacrylate]75 as the building unit (PHPMA35-b-PDPA75). The self-assemblies were produced with desired size towards long circulation time and tumor accumulation (hydrodynamic diameter - DH ~ 100 nm), and they could be successfully loaded with 10% w/w DOX (doxorubicin), while maintaining colloidal stability. The DOX loaded amount is presumably mainly burst-released at the acidic microenvironment of tumors thanks to the pH-switchable property of PDPA (pKa ~ 6.8), while reduced drug leakage has been monitored in pH 7.4. Compared to the administration of free DOX, the drug-loaded supramolecular structures greatly enhanced the therapeutic efficacy with effective growth inhibition of EL4 lymphoma tumor model and 100% survival rate in female C57BL/6 black mice over 40 days. The approach also led to reduced cardiotoxic effect. These features highlight the potential application of such nanotechnology-based treatment in a variety of cancer therapies where low local pH is commonly found, and emphasize PHPMA-based nanomedicines as an alternative to PEGylated formulations.

We report here the influence of hydrophobic terminal groups from RAFT chain transfer agent 4-cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl]pentanoic acid on the co-assembly behavior of two opposi...

Methylcellulose (MC) is a commercially important, water-soluble polysaccharide. Many food applications exploit the thermoreversible gelation behavior of MC in aqueous media. The mechanism of MC gel...

Hexagonal boron nitride (hBN) is a structural analog of graphene, with unique mechanical, thermal, and optical properties that make it desirable for a variety of applications. Production of stable ...

Background Cancer cell-derived extracellular vesicles (EVs) have previously been shown to contribute to pre-metastatic niche formation. Specifically, aggressive tumors secrete pro-metastatic EVs that travel in the circulation to distant organs to modulate the microenvironment for future metastatic spread. Previous studies have focused on the interface between pro-metastatic EVs and epithelial/endothelial cells in the pre-metastatic niche. However, EV interactions with circulating components such as low-density lipoprotein (LDL) have been overlooked. Results This study demonstrates that EVs derived from brain metastases cells (Br-EVs) and corresponding regular cancer cells (Reg-EVs) display different interactions with LDL. Specifically, Br-EVs trigger LDL aggregation, and the presence of LDL accelerates Br-EV uptake by monocytes, which are key components in the brain metastatic niche. Conclusions Collectively, these data are the first to demonstrate that pro-metastatic EVs display distinct interactions with LDL, which impacts monocyte internalization of EVs.

Chlorosulfonic acid and oleum are ideal solvents for enabling the transformation of disordered carbon nanotubes (CNTs) into precise and highly functional morphologies. Currently, processing these solvents using extrusion techniques presents complications due to chemical compatibility, which constrain equipment and substrate material options. Here, we present a novel acid solvent system based on methanesulfonic or p -toluenesulfonic acids with low corrosivity, which form true solutions of CNTs at concentrations as high as 10 g/liter (≈0.7 volume %). The versatility of this solvent system is demonstrated by drop-in application to conventional manufacturing processes such as slot die coating, solution spinning continuous fibers, and 3D printing aerogels. Through continuous slot coating, we achieve state-of-the-art optoelectronic performance (83.6 %T and 14 ohm/sq) at industrially relevant production speeds. This work establishes practical and efficient means for scalable processing of CNT into advanced materials with properties suitable for a wide range of applications.

Methylcellulose (MC) is a water-soluble cellulose derivative with a wide range of commercial applications. Upon heating, MC solutions reversibly form ∼15–20 nm diameter fibrils, which percolate int...

Many pharmaceutics are aqueous dispersions of small or large molecules, often self-assembled in complexes from a few to hundreds of molecules. In many cases, the dispersing liquid is non-aqueous. Many pharmaceutical preparations are very viscous. The efficacy of those dispersions is in many cases a function of the nanostructure of those complexes or aggregates. To study the nanostructure of those systems, one needs electron microscopy, the only way to obtain nanostructural information by recording direct images whose interpretation is not model-dependent. However, these methodologies are complicated by the need to make liquid systems compatible with high vacuum in electron microscopes. There are also issues related to the interaction of the electron beam with the specimen such as micrograph contrast, electron beam radiation damage, and artifacts associated with specimen preparation. In this article, which is focused on the state of the art of imaging self-assembled complexes, we briefly describe cryogenic temperature transmission electron microscopy (cryo-TEM) and cryogenic temperature scanning electron microcopy (cryo-SEM). We present the principles of these methodologies, give examples of their applications as analytical tools for pharmaceutics, and list their limitations and ways to avoid pitfalls in their application.

Microemulsions, as thermodynamically stable mixtures of oil, water, and surfactant, are known and have been studied for more than 70 years. However, even today there are still quite a number of unclear aspects, and more recent research work has modified and extended our picture. This review gives a short overview of how the understanding of microemulsions has developed, the current view on their properties and structural features, and in particular, how they are related to applications. We also discuss more recent developments regarding nonclassical microemulsions such as surfactant-free (ultraflexible) microemulsions or ones containing uncommon solvents or amphiphiles (like antagonistic salts). These new findings challenge to some extent our previous understanding of microemulsions, which therefore has to be extended to look at the different types of microemulsions in a unified way. In particular, the flexibility of the amphiphilic film is the key property to classify different microemulsion types and their properties in this review. Such a classification of microemulsions requires a thorough determination of their structural properties, and therefore, the experimental methods to determine microemulsion structure and dynamics are reviewed briefly, with a particular emphasis on recent developments in the field of direct imaging by means of electron microscopy. Based on this classification of microemulsions, we then discuss their applications, where the application demands have to be met by the properties of the microemulsion, which in turn are controlled by the flexibility of their amphiphilic interface. Another frequently important aspect for applications is the control of the rheological properties. Normally, microemulsions are low viscous and therefore enhancing viscosity has to be achieved by either having high concentrations (often not wished for) or additives, which do not significantly interfere with the microemulsion. Accordingly, this review gives a comprehensive account of the properties of microemulsions, including most recent developments and bringing them together from a united viewpoint, with an emphasis on how this affects the way of formulating microemulsions for a given application with desired properties., T.Z. thanks the German Science Foundation (DFG) for providing a Mercator professorship within the International Research Training Group (IRTG) 1524 (SSNI) at the Technische Universität Berlin, as well as the Agence Nationale de la Recherche (ANR) for the LABEX “Chemisyst” grant ANR 2011-01-05 that made the long-term collaboration possible.

Boron nitride nanotubes (BNNT) are poised to fill an electrically insulating, high-temperature, high-strength niche. Despite significant progress over the past two decades, BNNTs are not yet synthesized in high enough quantity and quality to permit their use in engineering applications. The next necessary step to make BNNTs accessible for research and applications is to improve the availability of high-quality BNNTs. Here, we present a scalable bulk purification technique that yields high-purity BNNTs. Bulk synthesized material is introduced to a wet oxygen environment at elevated temperatures to remove elemental boron and hexagonal boron nitride impurities with a final yield of purified BNNTs near 10 wt %. This process shows full removal of impurities, as observed by scanning electron microscopy (SEM), cryogenic transmission electron microscopy (TEM), and high-resolution TEM. X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy show minimal BNNT functionalization, while high-resolution TEM sh...

Monocyte-induced endothelial cell inflammation is associated with multiple pathological conditions, and extracellular vesicles (EVs) are essential nanosized components of intercellular communication. EVs derived from endotoxin-stimulated monocytes were previously shown to carry pro-inflammatory proteins and RNAs. The role of glucose transporter-1 (GLUT-1) and glycan features in monocyte-derived EV-induced endothelial cell inflammation remains largely unexplored. This study demonstrates that EVs derived from endotoxin-stimulated monocytes activate inflammatory pathways in endothelial cells, which are partially attributed to GLUT-1. Alterations in glycan features and increased levels of GLUT-1 were observed in EVs derived from endotoxin-stimulated monocytes. Notably, inhibition of EV-associated GLUT-1, through the use of fasentin, suppressed EV-induced inflammatory cytokines in recipient endothelial cells.

Cellulose-based oil-in-water (O/W) emulsions were studied by diffusing wave spectroscopy (DWS) regarding the effect of the cellulose concentration and mixing rate on the average droplet size, microrheological features and stability. Furthermore, the microstructure of these emulsions was imaged by cryo-scanning electron microscopy (cryo-SEM). The micrographs showed that cellulose was effectively adsorbed at the oil-water interface, resembling a film-like shell that protected the oil droplets from coalescing. The non-adsorbed cellulose that was observed in the continuous aqueous medium, contributed to the enhancement of the viscosity of the medium, leading to an improvement in the stability of the overall system. Generally, the higher the cellulose concentration and mixing rate, the smaller the emulsion droplets formed, and the higher was their stability. The combination of both techniques, DWS and cryo-SEM, revealed a very appealing and robust methodology for the characterization and design of novel emulsion-based formulations. FCT: PTDC/ASP-SIL/30619/2017, UIDB/05183/2020 / CEECIND/01014/2018 info:eu-repo/semantics/publishedVersion

Hypothesis The structure, rheology and other physicochemical properties of dilute aqueous dispersions of sodium oleate (NaOL) are well known. This paper is the first report in which a moderately concentrated (13% w/w) dispersion of NaOL in water is investigated. In fact, at this concentration the phase and rheology behavior of the surfactant remarkably deviates from those of its dilute solutions in water and a significant effect is imparted by the addition of potassium chloride. Experimental The structural, thermal and rheological properties of a 13% w/w dispersion of NaOL in water were investigated by cryo-TEM, rheology, and DSC experiments with and without the addition of potassium chloride. The system is comprised of elongated wormlike micelles that turn into a gel-like more disordered viscous material upon addition of small amounts of KCl (4% w/w). Findings This paper illustrates the multifaceted behavior of sodium oleate dispersions at intermediate concentrations that depends on the presence of other cosolutes (such as KCl). The results show that viscoelastic aqueous dispersions of NaOL are excellent candidates for the preparation of stimuli-responsive green materials to be used in a number of different applications. We also discuss the genesis of wormlike micelles (WLMs) in terms of the general theory of self-assembly.

For the past twenty years, significant progress has been made in both developing cryogenic transmission electron microscopy (cryo-TEM) technology and understanding assembled behavior of amphiphilic molecules. Cryo-TEM can provide high-resolution images of complex fluids in a near state. Samples embedded in a thin layer of vitrified solvent do not exhibit artifacts that would normally occur when using chemical fixation or staining-and-drying techniques. Cryo-TEM has been useful in imaging biological molecules in aqueous solutions. Cryo-TEM has become a powerful tool in the study of -assembled structures of amphiphiles in solution as a complementary tool to small-angle X-ray and neutron scattering, light scattering, rheology measurements, and nuclear magnetic resonance. The application of cryo-TEM in the study of assembled behavior of amphiphilic block copolymers, hydrogels, and other complex soft systems continues to emerge. In this context, the usage of cryo-TEM in the field of amphiphilic complex fluids and self-assembled nano-materials is briefly reviewed, and its unique role in exploring the nature of assembled structure in liquid suspension is highlighted.

Self-assembled aggregates formed by semidilute polyanion hyaluronan (hyaluronic acid, HA) and an oppositely charged surfactant tetradecyltrimethylammonium bromide (TTAB) in an aqueous phosphate-buffered saline (PBS) solution have been studied via light scattering (LS), small-angle neutron scattering (SANS), and cryogenic transmission electron microscopy (cryo-TEM). The addition of 0-20 mM TTAB to a 27.7 mM (monomer, 1 wt %) HA solution (597 kDa) in PBS buffer leads to soluble complexes until phase separation occurs near charge equilibrium (20 mM TTAB). While the viscosity remains rather constant, already small amounts of added TTAB lead to the formation of large globular superstructures, which are built in a hierarchical fashion from a locally threadlike structural arrangement of TTA micelles along the stiff HA chains, within the little changed HA network. These globular domains have radii of 60-100 nm and contain 500-700 TTA micelles, which means that they are very "fluffy" and composed of about 99% water. They do not grow in size or number upon further TTAB addition, but, instead, the additional TTA micelles form further threadlike complexes outside of the big globular domains. Such a type of polyelectrolyte-surfactant complexes (PESCs) has not been described before and has to be attributed to the particular properties of HA, which are high stiffness and relatively weak interactions with oppositely charged micelles due to having the charged carboxylic group close to the polysaccharide backbone. These findings demonstrate that the HA network structure in solution basically remains unaffected by complexation with an oppositely charged surfactant, explaining the unchanged rheological behavior and the formation of a unique PESC local "coacervate" structure within the HA hydrogel network.

International audience; We studied polyelectrolyte/microemulsion complexes (PEMECs) formed by the biopolymer sodium hyaluronate (NaHA) and cationic oil-in-water (O/W) microemulsion droplets. Around equimolar charge conditions, a two-phase region with a liquid−liquid phase separation (coacervate formation) is observed, while mixed complexes are formed at polyelectrolyte excess. The largest complexes are found close to the phase boundary. The detailed structure of these complexes was determined by a combination of static and dynamic light scattering (SLS and DLS), small-angle neutron scattering (SANS), and cryo-transmission electron cryomicroscopy (cryo-TEM). Interestingly, these complexes formed with NaHA are much more elongated compared to previously studied complexes formed with sodium polyacrylate (NaPA). Similar observations were made for another polysaccharide, sodium carboxymethyl cellulose (NaCMC). Apparently, the persistence length of the complexes is largely proportional to the persistence length of the polyelectrolyte, which was determined by analyzing the SANS data with a specifically developed model. Accordingly, the size of the complexes formed with stiffer biopolyelectrolytes becomes much larger, increasing with the molecular weight (M w) of the polyelectrolyte. In summary, we conclude that the size and structure of the PEMECs can be controlled by the type of polyelectrolyte, mixing ratio, size of the microemulsion droplets, and M w of the polyelectrolyte. This means that the polyelectrolyte addition can be used as a key structuring element for the size and shape of such complexes.

With the aim of engineering multifunctional nanoparticles useful for cancer therapy, a diketopyrrolopyrrole-porphyrin based photosensitizer was here conjugated to a block copolymer (Pluronic F108), and used to stabilize in water lipidic cubic liquid crystalline nanoparticles (cubosomes), also loaded with the antineoplastic agent docetaxel. The physicochemical characterization by SAXS, DLS, and cryo-TEM demonstrated that the formulation consisted of cubosomes, about 150 nm in size, possessing a bicontinuous cubic structure (space group Pn3m). The cellular imaging experiments proved that these nanoparticles localized in lysosomes and mitochondria, while cytotoxicity tests evidenced a slight but significant synergistic effect which, after irradiation, increased the toxicity induced by docetaxel alone, allowing further reduction of cell viability.

The radical emulsion copolymerization of vinylidene fluoride (VDF) with perfluoromethyl vinyl ether (PMVE), initiated by potassium persulfate in the presence or absence of a surfactant is presented. The surfactant used in this copolymerization was 3-hydroxy-2-trifluoromethyl propanoic acid (MAF-OH). The VDF mol% ranged between 60 and 90 mol%. Molar masses up to 103 000 g mol−1 with wide dispersities (Đ > 2) were produced with yields up to 74%. The composition of the resulting poly(VDF-co-PMVE) copolymers was determined by 19F NMR spectroscopy. Under certain conditions (60% VDF mol% in the autoclave inlet, MAF-OH and a low total monomer concentration), the produced latexes were stable and showed an average particle size of ca. 200 nm, as observed using a Zetasizer and a cryo-TEM. Semi-crystalline copolymers were obtained when the VDF mol% was higher than 80 mol%. These copolymers exhibit high thermostability (their degradation under air started at 400 °C). A central point 23 factorial experimental design was conducted aiming at the identification of the influence of the parameters on the reaction and the end-use properties of the polymers. Most of the studied properties were highly influenced by the VDF mol%. The highest molar mass was obtained using 90 mol% VDF in the feed, no surfactant, and a total monomer molar amount of 208 mmol, while the highest dispersity was obtained using 60 mol% VDF in the feed, no surfactant, and a total monomer molar amount of 208 mmol.

We present here a technology to microencapsulate drugs by the sol-gel process, and cryo-SEM methodology that allows the nanostructural characterization of the formed capsules in their native state without any artifacts, related to their drying prior to imaging. The methodology utilizes three signals generated by the electron beam scanning the specimen: Secondary electrons, backscattered electrons, and x-rays. The first gives topographical information of the fracture-surface of the thermally-fixed specimen, the second gives contrast between elements of different atomic numbers, and the third allows the identification of those elements. Combined, the three signals provide full microstructural characterization of the studied specimen. Using this methodology, we were able to demonstrate that the sol-gel technology does indeed enable the encapsulation of two hydrophobic active molecules with a silica shell. This technology allows the active ingredient in the drug product to slowly migrate from the microcapsule onto the skin, thus obtaining the desired effect with minimal side-effects, as was exhibited in several clinical studies. The successful application of the cryo-SEM methodology in this case, demonstrates that it can be used to characterize a wide range of liquid-phase suspensions, in their native state, with minimal specimen preparation or imaging artifacts.

Cellulose can be dissolved in concentrated acidic aqueous solvents forming extremely viscous solutions, and, in some cases, liquid crystalline phases. In this work, the concentrated phosphoric acid aqueous solvent is revisited implementing a set of advanced techniques, such as cryo-transmission electronic microscopy (cryo-TEM), polarization transfer solid-state nuclear magnetic resonance (PTssNMR), and diffusing wave spectroscopy (DWS). Cryo-TEM images confirm that this solvent system is capable to efficiently dissolve cellulose. No cellulose particles, fibrils, or aggregates are visible. Conversely, PTssNMR revealed a dominant CP signal at 25 °C, characteristic of C-H bond reorientation with correlation time longer than 100 ns and/or order parameter above 0.5, which was ascribed to a transient gel-like network or an anisotropic liquid crystalline phase. Increasing the temperature leads to a gradual transition from CP to INEPT-dominant signal and a loss of birefringence in optical microscopy, suggesting an anisotropic-to-isotropic phase transition. Finally, an excellent agreement between optical microrheology and conventional mechanical rheometry was also obtained.

The unique carbon nanotube (CNT) properties are mainly determined by their geometry, e.g., their aspect ratio, diameter, and number of walls. So far, chlorosulfonic acid is the only practical true solvent for carbon nanotubes, forming thermodynamically stable molecular solutions. Above a critical concentration the system forms an ordered, nematic liquid-crystalline phase. That phase behavior is the basis for liquid-phase processing and the optimal translation of the carbon nanotube molecular properties to the macroscopic scale. The final material properties depend on the phase behavior of the "dope" from which it is prepared, which depends on the CNT parameters themselves. Earlier work determined that CNT aspect ratio controls the phase behavior, in accordance with classical rigid-rod theories. Here we use cryogenic transmission electron microscopy and Raman spectroscopy to understand the relation between the geometry of the CNTs, the chemical interaction with chlorosulfonic acid, and the phase behavior of crowded solutions. We show that the CNT diameter and number of walls also play an independent role in the phase transition and phase morphology of the system because of their effect on the CNT bending stiffness.

This work focuses on the synthesis and self-assembly of triphilic poly(2-oxazoline) triblock copolymers with high fluorine content toward our future aim of developing poly(2-oxazoline) magnetic resonance imaging (MRI) contrast agents. A highly fluorinated 2-substituted-2-oxazoline monomer, namely 2-(1H,1H,2H,2H-perfluorooctyl)-2-oxazoline, was synthesized using the Grignard reaction. The polymerization kinetics of the synthesized monomer was studied, and it was used for the preparation of triblock copolymers with hydrophilic 2-methyl-2-oxazoline, hydrophobic 2-octyl-2-oxazoline, and fluorophilic blocks by cationic ring-opening polymerization yielding polymers with low relatively dispersity (1.21.4). The presence of the blocks with the different nature in one copolymer structure facilitated self-assembly of the copolymers in water and dimethyl sulfoxide as observed by dynamic light scattering, cryo-transmission electron microscopy, and small-angle neutron scattering. The nanoparticle morphology is strongly influenced by the order and length of each block and the nature of solvent, leading to nanoparticles with coreshell structure as confirmed by small-angle neutron scattering. The reported poly(2-oxazoline) block copolymers with high fluorine content have high potential for future development of MRI contrast agents.

In this paper we investigated the effect of quaternary ammonium bromide, R4NBr(R = methyl, ethyl, propyl, butyl) on the micellization of the CTAB/long-chain alcohol (C9OH-C12OH) micellar system using viscosity, rheology, dynamic light scattering (DLS), and cryo-TEM analysis. The results indicates that, apart from concentration (C0), and chain length of alcohol (n), micellar properties of the CTAB/R4NBr/alcohol system showed a strong dependence on alkyl chain length of R4NBr. The viscosity behavior of CTAB/R4NBr with C0 was similar to our previous studied system, CTAB/KBr/alcohol, and is attributed to alcohol induced morphological transition. The viscosity, rheology, and DLS analysis reveal the dependence of n on the micellar growth of the CTAB/R4NBr/alcohol system. The result showed tetra butyl ammonium bromide (Bu4N+) as least effective to induce micellar growth in the CTAB/alcohol system compared to other quaternary ammonium salts. This is discussed on the basis of change in solubilization behavior with the chain length of R4NBr. The cryo-TEM analysis of the CTAB/R4NBr/alcohol micellar system showed vesicles to short rod-like micelle transition on changing R from methyl to butyl, confirming the effectiveness of quaternary ammonium bromide in tuning morphological transition in the system.

Using direct-imaging cryogenic transmission and scanning electron microscopy, we show different stages of liquid-crystalline phase development in progressively more concentrated solutions of carbon nanotubes in chlorosulfonic acid: a dilute phase of individually dissolved carbon nanotubes; semidilute and concentrated isotropic phases; coexisting concentrated isotropic and nematic phases in local equilibrium with each other; and a fully liquid-crystalline phase. Nanometric resolution of cryogenic electron microscopy reveals carbon nanotube self-assembly into liquid-crystalline domains of several nanometers in width at very early stages. We find significant differences in carbon nanotube liquid-crystalline domain morphology as a function of the carbon nanotube aspect ratio, diameter, and degree of purity.

Unusual temperature gaps have previously been observed in the turbulent drag reduction effectiveness of Dobon and Habon cationic surfactant systems containing two anionic counterions of different binding strengths. Here, we report drag reduction data for a cationic surfactant with a mixture of dodecyl sulfate and tosylate counterions showing a temperature gap. Cryo-TEM images of nanostructures at different temperatures for this system support an explanation for this gap, based on the counterions’ relative binding strengths.

We have formulated and investigated innovative lipid-based nanoparticles characterized by a reverse hexagonal liquid crystalline inner structure (hexosomes). These nanoparticles were doped with a potent, highly water insoluble anticancer drug, namely docetaxel, and stabilized by a mixture of commercial and folate- and rhodamine-conjugated Pluronic F108. Thus, they simultaneously possess therapeutic, imaging, and targeting properties toward cancer cells. The morphological and structural aspects of the hexosomes were investigated at different temperatures (10, 25, 37, and 50 °C), and our results demonstrate good performance in terms of stability of these nanoparticles. The latter was furthermore confirmed by the very slow and continuous release profile of docetaxel observed in drug release experiments. Although it was not possible to assess a specific compartmentalization of the dye, this formulation allowed the successful visualization of HeLa cells. Finally, cytotoxic assays showed a 20-fold higher toxic effect of the drug-doped hexosomes against HeLa cells with respect to the free (not loaded in hexosomes) anticancer drug. On the whole, these results indicate that this formulation is a potential theranostic tool in oncology.