Oxidation of Unsaturated Aldehydes by Organic Peracids

The paper is dedicated to studies of kinetic regularities of oxidation of unsaturated aldehydes by organic peracids. The routes of products formation were considered, kinetic model of the oxidation reaction was designed and reaction activation parameters were calculated based on experimental data. New data on reactivity of aldehydes with various structures in the reaction with peracids were obtained.

Role of the Perivascular Epithelium in the Histogenesis of Hassall's Corpuscles

Thirteen human thymuses and one thymoma were morphologically and immunohistologically investigated to define the histogenesis of Hassall's corpuscles (HCs). The following monoclonal antibodies: antisquamous cytokeratin on paraffin sections and TE-4 and TE-8 on frozen sections, were used to show the distribution of the epithelial components; PAL-E on frozen and anti-CD31 and anti-CD34 on paraffin sections detected the endothelial cell distribution. In the thymoma, epithelial onion-like structures, looking like true HCs, were found to originate from the perivascular epithelium lining dilatated spaces and some of them partially obliterated the space where the blood capillary showed thickened wall and endothelial regressive changes. Antisquamous cytokeratin stained: (1) in the thymus: subcapsular, medullary, and HC epithelial cells; (2) in the thymoma: epithelial cells lining the perivascular spaces and forming HCs. TE-4 stained: (1) in the thymus: the subcapsular and medullary epithelium; (2) in the thymoma: the epithelium lining the perivascular spaces and epithelial cells forming HCs. TE-8 stained: (1) in the thymus: HCs only; (2) in the thymoma: HCs and perivascular epithelial cells. PAL-E, CD31, and CD34, which specifically react with endothelial cells, stained remnants of capillary structures in the core of some HCs. The results indicate that: (1) corpuscular structures in thymoma originate from perivascular epithelium; (2) thymus medullary epithelial cells stained by cytokeratin and TE-4 correspond to perivascular epithelial cells whose staining is well documented in thymoma; (3) the subcapsular-perivascular epithelium and HCs represent different steps of differentiation of a single ectodermal cell lineage; (4) the PAL-E-, CD31-, and CD34-positive reaction in the core of some HCs suggests that the perivascular epithelium would be stimulated to transform into HCs as a consequence of endothelial changes with fragmentation of the capillary included in the perivascular space.

Mixing of Two Immiscible Liquids within the Polymer Microgel Adsorbed at Their Interface

We report on the behavior of two immiscible liquids within polymer microgel adsorbed at their interface. By means of dissipative particle dynamics (DPD) simulations and theoretical analysis in the framework of the Flory-Huggins (FH) lattice theory, we demonstrate that the microgel acts as a "compatibilizer" of these liquids: their miscibility within the microgel increases considerably. If the incompatibility of the liquids is moderate, although strong enough to induce phase separation in their 1:1 composition, they form homogeneous mixture in the microgel interior. The mixture of highly incompatible liquids undergoes separation into two (micro)phases within the microgel likewise out of it; however, the segregation regime is weaker and the concentration profiles are characterized by a weaker decay (gradient) in comparison with those of two pure liquids. The enhanced miscibility is a result of the screening of unfavorable interactions between unlike liquid molecules by polymer subchains. We have shown that better miscibility of the liquids is achieved with densely cross-linked microgels. Our findings are very perspective for many applications where immiscible species have to be mixed at interfaces (like in heterogeneous catalysis).

Reversible Size Modulation of Aqueous Microgels via Orthogonal or Combined Application of Thermo- and Phototriggers

Aqueous microgels that respond orthogonally to external temperature and light stimuli and to a combination of both stimuli were developed. N-Vinylcaprolactam (VCL) was copolymerized with small feed amounts (<5 mol %) of 4-[(4-methacryloyloxy)phenylazo] benzenesulfonic acid (ABSA) and cross-linked with N,N'-methylenebis(acrylamide) (BIS) to synthesize monodisperse and colloidally stable P(VCL-BIS-ABSA) microgels. The volume phase transition information on the microgels under both orthogonal and combined application of temperature and light stimuli was investigated in situ by dynamic light scattering (DLS) instrument. Modeling of this information by the Flory-Rehner theory describes and aids the preliminary understanding of the main features in the volume phase transition of these photoresponsive microgels. Interestingly, the microgels rapidly deswell upon UV irradiation (λ = 365 nm), even as the trans-ABSA pendant groups are converted to the more polar cis state. The variation in the content of the pendant azobenzene groups in the microgels allows for reversible modulation of the phototriggered volume change. We propose that the approach of the sulfonic acid groups of cis-ABSA toward the polymer backbone causes the disruption of hydrogen bonding interactions between water molecules and the carbonyl groups of VCL.

In-line Monitoring of Monomer and Polymer Content During Microgel Synthesis Using Precipitation Polymerization via Raman Spectroscopy and Indirect Hard Modeling

This contribution presents in-line monitoring of microgel synthesis by precipitation polymerization based on Raman spectroscopy. The spectra are evaluated via multivariate Indirect Hard Modeling (IHM) regression. Therefore, mechanistic models of the pure component spectra for solvent, monomer, and microgel are created by a sum of adaptable parameterized peak functions (Gaussian-Lorentzian). Instead of individual calibrations for each analyte, one comprehensive model is calibrated to predict both the monomer and microgel fraction while ensuring a consistent mass balance. As a novelty, this leads to an in-line microgel quantification based on an interactive spectral model. The results show cross-validation errors (RMSECV) of monomer and microgel fractions as low as 0.028 wt % and 0.084 wt %, respectively. The ability of IHM to account for non-linear spectral changes was found to reduce the microgel RMSECV by a factor of two compared to linear CLS regression. The calibration model allows simultaneous observation of the decrease in monomer content and the formation of microgels. Long as well as short focus immersion optics reveal characteristic vibrations of the turbid microgel suspension, although long focus optics are influenced by scattering particles to a greater extent. Precise examination of the model proves that the prediction is robust against changes in microgel particle size or temperature, which opens up the application of Raman spectroscopy as a comprehensive process analytical technology in microgel synthesis.

When Colloidal Particles Become Polymer Coils

This work concerns interfacial adsorption and attachment of swollen microgel with low- to medium-level cross-linking density. Compared to colloids that form a second, dispersed phase, the suspended swollen microgel particles are ultrahigh molecular weight molecules, which are dissolved like a linear polymer, so that solvent and solute constitute only one phase. In contrast to recent literature in which microgels are treated as particles with a distinct surface, we consider solvent-solute interaction as well as interfacial adsorption based on the chain segments that can form trains of adsorbed segments and loops protruding from the surface into the solvent. We point out experimental results that support this discrimination between particles and microgels. The time needed for swollen microgels to adsorb at the air/water interface can be 3 orders of magnitude shorter than that for dispersed particles and decreases with decreasing cross-linking density. Detailed analysis of the microgels deformation, in the dry state, at a solid surface enabled discrimination particle like microgel in which case spreading was controlled predominantly by the elasticity and molecule like adsorption characterized by a significant overstreching, ultimately leading to chain scission of microgel strands. Dissipative particle dynamics simulations confirms the experimental findings on the interfacial activity and spreading of microgel at liquid/air interface.

Ultrasmall functional ZnO2 nanoparticles: synthesis, characterization and oxygen release properties

Ultrasmall zinc peroxide nanoparticles with diameter between 3.3 ± 0.9 and 14.4 ± 5.2 nm were synthesized via a completely new synthesis method (high-pressure impinging-jet reactor; MRT CR 5, Microfluidics®).

The next step in precipitation polymerization of N-isopropylacrylamide: particle number density control by monochain globule surface charge modulation

Many applications of poly(N-isopropylacrylamide) microgels necessitate robust control over particle size.

Responsive microgels with supramolecular crosslinks: synthesis and triggered degradation in aqueous medium

Stimuli-responsive microgels containing supramolecular crosslinks based on cholesteryl/β-cyclodextrin interactions were synthesized and degraded upon addition of 1-adamantanecarboxylic acid.

Temperature and pH dual-responsive poly(vinyl lactam) copolymers functionalized with amine side groups via RAFT polymerization

A series of statistical copolymers based on cyclic N-vinyl lactams and N-vinylformamide were synthesized via RAFT polymerization. Tempertaure/pH dual responsive polymers were obtained via hydrolysis the copolymers in alkaline conditions.

Stimuli-responsive poly(N-vinylcaprolactam-co-2-methoxyethyl acrylate) core–shell microgels: facile synthesis, modulation of surface properties and controlled internalisation into cells

Poly(N-vinylcaprolactam-co-2-methoxyethyl acrylate) core–shell microgels as imaging/diagnostic system.

Facile synthesis of dumbbell-shaped multi-compartment nanoparticles

In this article we report on the controlled synthesis of asymmetric lemon-shaped and dumbbell-shaped multi-compartment nanoparticles (MCPs) with a reactive surface and interesting morphology. In our approach we utilize partial coating of hematite ellipsoids with a hydrophobic polymer layer followed by selective silica deposition on the non-coated surface. Ellipsoidal hematite particles provide a non-centric asymmetry, which is strongly enhanced during the seeded emulsion polymerization. The asymmetric growth of polymers on the hematite particle surface is driven by phase separation phenomena, which lead to a reduction of the interfacial tension. We found the tips of the hematite ellipsoids to be uncovered after polymerization. A selective deposition of silica onto the free tips leads to dumbbell-shaped particles with hydrophilic and hydrophobic parts.

Theranostic USPIO-Loaded Microbubbles for Mediating and Monitoring Blood-Brain Barrier Permeation

Efficient and safe drug delivery across the blood-brain barrier (BBB) remains to be one of the major challenges of biomedical and (nano-) pharmaceutical research. Here, we show that poly(butyl cyanoacrylate)-based microbubbles (MB), carrying ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles within their shell, can be used to mediate and monitor BBB permeation. Upon exposure to transcranial ultrasound pulses, USPIO-MB are destroyed, resulting in acoustic forces inducing vessel permeability. At the same time, USPIO are released from the MB shell, they extravasate across the permeabilized BBB and they accumulate in extravascular brain tissue, thereby providing non-invasive R₂*-based magnetic resonance imaging information on the extent of BBB opening. Quantitative changes in R₂* relaxometry were in good agreement with 2D and 3D microscopy results on the extravascular deposition of the macromolecular model drug FITC-dextran into the brain. Such theranostic materials and methods are considered to be useful for mediating and monitoring drug delivery across the BBB, and for enabling safe and efficient treatment of CNS disorders.

Microgel-functionalised fibres with pH-optimised degradation behaviour – a promising approach for short-term medical applications

Resorbable polymers have been established for several decades in biomedical applications. The most frequently used resorbable polymers are still the aliphatic polyesters polylactides (PLA), polyglycolid (PGA) and polycaprolactone (PCL) homo- and copolymers. However, inherent pH dropping during degradation of some biomaterials may provoke inflammation and, thus, hamper the healing process. In this study we investigate the manufacturing method of microgel functionalised PLA Fibres in a dry-spinning process and the buffering effect of the poly(N-vinylcaprolactam-co-acetoacetoxyethyl methacrylate) vinylimidazole (VCL/AAEM/Vlm) microgels during the degradation of the fibres. Furthermore we examine the biocompatibility of the produced fibres and established a mathematical model to describe and analyse the pH level in the vicinity of the PLA fibre.

Monitoring the internal structure of poly(N-vinylcaprolactam) microgels with variable cross-link concentration

The combination of a set of complementary techniques allows us to construct an unprecedented and comprehensive picture of the internal structure, temperature dependent swelling behavior, and the dependence of these properties on the cross-linker concentration of microgel particles based on N-vinylcaprolactam (VCL). The microgels were synthesized by precipitation polymerization using different amounts of cross-linking agent. Characterization was performed by small-angle neutron scattering (SANS) using two complementary neutron instruments to cover a uniquely broad Q-range with one probe. Additionally we used dynamic light scattering (DLS), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). Previously obtained nuclear magnetic resonance spectroscopy (NMR) results on the same PVCL particles are utilized to round the picture off. Our study shows that both the particle radius and the cross-link density and therefore also the stiffness of the microgels rises with increasing cross-linker content. Hence, more cross-linker reduces the swelling capability distinctly. These findings are supported by SANS and AFM measurements. Independent DLS experiments also found the increase in particle size but suggest an unchanged cross-link density. The reason for the apparent contradiction is the indirect extraction of the parameters via a model in the evaluation of DLS measurements. The more direct approach in AFM by evaluating the cross section profiles of observed microgel particles gives evidence of significantly softer and more deformable particles at lower cross-linker concentrations and therefore verifies the change in cross-link density. DSC data indicate a minor but unexpected shift of the volume phase transition temperature (VPTT) to higher temperatures and exposes a more heterogeneous internal structure of the microgels with increasing cross-link density. Moreover, a change in the total energy transfer during the VPT gives evidence that the strength of hydrogen bonds is significantly affected by the cross-link density. A strong and reproducible deviation of the material density of the cross-linked microgel polymer chains toward a higher value compared to the respective linear chains has yet to be explained.

QCD and strongly coupled gauge theories: challenges and perspectives

We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.