Crowding effects on the structure and rheology of ultrasoft PNIPAM-PEGMA copolymer microgels.

We investigate the link between the internal microstructure of poly(-isopropylacrylamide)-poly(ethylene glycol) methyl ether methacrylate (PNIPAM-PEGMA) microgels, their bulk moduli and the rheological response and structural arrangement in dense suspensions. The low degree of crosslinking combined with the increased hydrophilicity induced by the presence of PEGMA results in a diffuse, star-like density profile of the particle and very low values of the bulk modulus in dilute conditions, as determined by small angle neutron scattering (SANS). The ultrasoft nature of the particle is reflected in the changes of the structural arrangement in dense suspensions, which evidence a strong deswelling and a sharp rise of the bulk modulus at moderate packing fractions.

Phase behavior of binary mixtures of hollow and regular microgels.

Soft colloids are widely used to study glass transition, aging and jamming. A high size polydispersity is typically introduced in these systems to avoid crystal formation. Here, we use binary mixtures of hollow and regular microgels with comparable sizes to inhibit crystallization.

Fluid-solid transitions in photonic crystals of soft, thermoresponsive microgels.

Microgels are often discussed as well-suited model system for soft colloids. In contrast to rigid spheres, the microgel volume and, coupled to this, the volume fraction in dispersion can be manipulated by external stimuli. This behavior is particularly interesting at high packings where phase transitions can be induced by external triggers such as temperature in the case of thermoresponsive microgels.

Self-Healing of Charged Microgels in Neutral and Charged Environments.

The softness of microgels depends on many aspects, such as particle characteristic lengths, sample concentration, chemical composition of the sample, and elastic moduli of the particle. Here, the response to crowding of ionic microgels is studied. Charged and uncharged ionic microgels are studied in concentrated suspensions of both neutral and ionic microgels with the same swollen size.

Beyond simple self-healing: How anisotropic nanogels adapt their shape to their environment.

The response of soft colloids to crowding depends sensitively on the particles' compressibility. Nanogel suspensions provide model systems that are often studied to better understand the properties of soft materials and complex fluids from the formation of colloidal crystals to the flow of viruses, blood, or platelet cells in the body. Large spherical nanogels, when embedded in a matrix of smaller nanogels, have the unique ability to spontaneously deswell to match their size to that of the nanogel composing the matrix.

Experimental determination of the bulk moduli of hollow nanogels.

The softness of an object can be quantified by one of the fundamental elastic moduli. The bulk modulus of the particle is most appropriate in the presence of isotropic compressions. Here, we use small-angle neutron scattering with contrast variation to directly access the bulk modulus of polymeric nanocapsules - pNIPAM-based hollow nanogels.

Resolving the different bulk moduli within individual soft nanogels using small-angle neutron scattering.

The bulk modulus, , quantifies the elastic response of an object to an isotropic compression. For soft compressible colloids, knowing is essential to accurately predict the suspension response to crowding. Most colloids have complex architectures characterized by different softness, which additionally depends on compression.

Phase behavior of ultrasoft spheres show stable bcc lattices.

The phase behavior of supersoft spheres is explored using solutions of ultralow cross-linked poly(N-isopropylacrylamide)-based microgels as a model system. For these microgels, the effects of the electric charges on their surfaces can be neglected and therefore only the role of softness on the phase behavior is investigated. The samples show a liquid-to-crystal transition at higher volume fraction with respect to both hard spheres and stiffer microgels.

Light-responsive self-assembly of a cationic azobenzene surfactant at high concentration.

The formation of high-concentration mesophases by a cationic azobenzene photosurfactant is described for the first time. Using a combination of polarised optical microscopy and small-angle X-ray scattering, optically anisotropic, self-assembled structures with long-range order are reported. The mesophases are disrupted or lost upon UV irradiation.

NUrF-Optimization of in situ UV-vis and fluorescence and autonomous characterization techniques with small-angle neutron scattering instrumentation.

We have designed, built, and validated a (quasi)-simultaneous measurement platform called NUrF, which consists of neutron small-angle scattering, UV-visible, fluorescence, and densitometry techniques. In this contribution, we illustrate the concept and benefits of the NUrF setup combined with high-performance liquid chromatography pumps to automate the preparation and measurement of a mixture series of Brij35 nonionic surfactants with perfluorononanoic acid in the presence of a reporter fluorophore (pyrene).

An integrative toolbox to unlock the structure and dynamics of protein-surfactant complexes.

The interactions between protein and surfactants play an important role in the stability and performance of formulated products. Due to the high complexity of such interactions, multi-technique approaches are required to study these systems. Here, an integrative approach is used to investigate the various interactions in a model system composed of human growth hormone and sodium dodecyl sulfate.

Synthesis and characterisation of biocompatible organic-inorganic core-shell nanocomposite particles based on ureasils.

Organic-inorganic core-shell nanocomposites have attracted increasing attention for applications in imaging, controlled release, biomedical scaffolds and self-healing materials. While tunable properties can readily be achieved through the selection of complementary building blocks, synergistic enhancement requires management of the core-shell interface. In this work, we report a one-pot method to fabricate hybrid core-shell nanocomposite particles (CSNPs) based on ureasils.

A single-component photorheological fluid with light-responsive viscosity.

Viscoelastic fluids whose rheological properties are tunable with light have the potential to deliver significant impact in fields relying on a change in flow behavior, such as in-use tuning of combined efficient heat-transfer and drag-reduction agents, microfluidic flow and controlled encapsulation and release. However, simple, single-component systems must be developed to allow integration with these applications. Here, we report a single-component viscoelastic fluid, capable of a dramatic light-sensitive rheological response, from a neutral azobenzene photosurfactant, 4-hexyl-4'butyloxymonotetraethylene glycol (CAzoOCE) in water.

Structural characterization by scattering and spectroscopic methods and biological evaluation of polymeric micelles of poloxamines and TPGS as nanocarriers for miltefosine delivery.

Miltefosine (MF), an alkylphospholipid originally developed for breast cancer treatment, is a highly active drug for the treatment against leishmaniasis, a neglected tropical disease considered the world's second leading cause of death by a parasitic agent after malaria. MF exhibits dose-limiting gastrointestinal side effects in patients and its penetration through lipophilic barriers is reduced. In this work we propose a reformulation of MF by incorporating the drug to poly(ethylene)oxide (PEO)-based polymeric micelles, specifically, D-α-tocopheryl polyethylene glycol succinate (TPGS) and Tetronic block copolymers (T904 and T1107).

Anisotropic Hollow Microgels That Can Adapt Their Size, Shape, and Softness.

The development of soft anisotropic building blocks is of great interest for various applications in soft matter. Furthermore, such systems would be important model systems for ordering phenomena in fundamental soft matter science. In this work, we address the challenge of creating hollow and anisotropically shaped thermoresponsive microgels, polymeric networks with a solvent filled cavity in their center that are swollen in a good solvent.

Exploring the colloid-to-polymer transition for ultra-low crosslinked microgels from three to two dimensions.

Microgels are solvent-swollen nano- and microparticles that show prevalent colloidal-like behavior despite their polymeric nature. Here we study ultra-low crosslinked poly(N-isopropylacrylamide) microgels (ULC), which can behave like colloids or flexible polymers depending on dimensionality, compression or other external stimuli. Small-angle neutron scattering shows that the structure of the ULC microgels in bulk aqueous solution is characterized by a density profile that decays smoothly from the center to a fuzzy surface.

Probing the dynamic self-assembly behaviour of photoswitchable wormlike micelles in real-time.

Understanding the dynamic self-assembly behaviour of azobenzene photosurfactants (AzoPS) is crucial to advance their use in controlled release applications such as drug delivery and micellar catalysis. Currently, their behaviour in the equilibrium cis- and trans-photostationary states is more widely understood than during the photoisomerisation process itself. Here, we investigate the time-dependent self-assembly of the different photoisomers of a model neutral AzoPS, tetraethylene glycol mono(4',4-octyloxy,octyl-azobenzene) (C8AzoOC8E4) using small-angle neutron scattering (SANS).

Reverse relationships of water uptake and alkaline durability with hydrophilicity of imidazolium-based grafted anion-exchange membranes.

We found unprecedented reverse relationships in anion-exchange membranes (AEMs) for Pt-free alkaline fuel cell systems, i.e., the increase in hydrophobicity increased water uptake and susceptibility to hydrolysis.

Unlocking Structure-Self-Assembly Relationships in Cationic Azobenzene Photosurfactants.

Azobenzene photosurfactants are light-responsive amphiphiles that have garnered significant attention for diverse applications including delivery and sorting systems, phase transfer catalysis, and foam drainage. The azobenzene chromophore changes both its polarity and conformation (trans-cis isomerization) in response to UV light, while the amphiphilic structure drives self-assembly. Detailed understanding of the inherent relationship between the molecular structure, physicochemical behavior, and micellar arrangement of azobenzene photosurfactants is critical to their usefulness.

Association and Internal Morphology of Self-Assembled HPPhOx/BSA Hybrid Nanoparticles in Aqueous Solutions.

We investigate the formation of hybrid polyelectrolyte/protein nanoparticles by associations between aggregates of partially hydrolyzed poly(2-phenyl-2-oxazoline) (HPPhOx) and bovine serum albumin (BSA) in aqueous solutions. Light scattering experiments show that at conditions of low salt, BSA creates interaggregate bridges and increases the size of the HPPhOx nanoparticles. At high salt contents, breaking of aggregates leads to well-defined nanoparticles.

Hollow microgels squeezed in overcrowded environments.

We study how a cavity changes the response of hollow microgels with respect to regular ones in overcrowded environments. The structural changes of hollow poly(N-isopropylacrylamide) microgels embedded within a matrix of regular ones are probed by small-angle neutron scattering with contrast variation. The form factors of the microgels at increasing compressions are directly measured.

Facially Amphipathic Glycopolymers Inhibit Ice Recrystallization.

Antifreeze glycoproteins (AFGPs) from polar fish are the most potent ice recrystallization (growth) inhibitors known, and synthetic mimics are required for low-temperature applications such as cell cryopreservation. Here we introduce facially amphipathic glycopolymers that mimic the three-dimensional structure of AFGPs. Glycopolymers featuring segregated hydrophilic and hydrophobic faces were prepared by ring-opening metathesis polymerization, and their rigid conformation was confirmed by small-angle neutron scattering.

The high-intensity option of the SANS diffractometer KWS-2 at JCNS - characterization and performance of the new multi-megahertz detection system.

A new detection system based on an array of He tubes and innovative fast detection electronics has been installed on the high-intensity small-angle neutron scattering (SANS) diffractometer KWS-2 operated by the Jülich Centre for Neutron Science (JCNS) at the Heinz Meier-Leibnitz Zentrum in Garching, Germany. The new detection system is composed of 18 eight-pack modules of He tubes that work independently of one another (each unit has its own processor and electronics). To improve the read-out characteristics and reduce the noise, the detection electronics are mounted in a closed case on the rear of the He tubes' frame.

Self-Templated Generation of Triggerable and Restorable Nonequilibrium Micelles.

Conditional variations can lead to micellar transformations resulting in various (equilibrium) morphologies. However, creating differently shaped assemblies under the same final conditions (same ingredients, composition, temperature, etc.) is challenging.