Thomas Hellweg

• Prof. Dr.
• Professor (Full) at Bielefeld University

A confined bicontinuous C 10 E 4 -D 2 O- n -octane microemulsion is studied using neutron spin-echo spectroscopy (NSE). Controlled pore glasses serve as confining matrices with pore diameters ranging from 24 to 112 nm. Firstly,...

We use small-angle neutron scattering (SANS) to investigate the structure and phase behavior of a complex fluid within meso- and macroporous matrices. Specifically, bicontinuous microemulsions of the temperature-dependent ternary system C10E4–water–n-octane are investigated in controlled pore glass (CPG) membranes with nominal pore diameters of 10...

Microplastic pollution and the urgent need for sustainable agriculture have raised interest in developing degradable carriers for controlled agrochemical release. Porous polymeric particles are particularly promising due to their unique release profiles compared to solid or core‐shell carriers. However, creating degradable, mesoporous (2–50 nm) mic...

We analyze the swelling behavior of N -isopropylacrylamide (NIPAM)-based microgels incorporating the non-thermoresponsive comonomer N - tert -butylacrylamide (NtBAM) using photon correlation spectroscopy (PCS) and atomic force microscopy (AFM). Previous thermodynamic analysis of PNIPAM-co-NtBAM microgel swelling relied on the classical Flory-Rehner...

Polymer cubosomes (PCs) are a recent class of self-assembled block copolymer (BCP) microparticles with an accessible periodic channel system. Most reported PCs consist of a polystyrene scaffold, which provides mechanical stability for templating but has a limited intrinsic functionality. Here, we report the synthesis of photocleavable BCPs with com...

In the present work, the temperature-dependent phase behavior of a C10E4 based microemulsion is studied in different meso–macroporous glasses, as a function of their pore diameter. The phase behavior in these pores is investigated by small-angle X-ray scattering (SAXS). The crucial parameter we discuss based on the SAXS results is the domain size o...

The formation and properties of smart (stimuli-responsive) membranes are reviewed, with a special focus on temperature and pH triggering of gating to water, ions, polymers, nanoparticles, or other molecules of interest. The review is organized in two parts, starting with all-smart membranes based on intrinsically smart materials, in particular of t...

The properties of pH‐responsive microgels are strongly influenced by the pH value during synthesis. In this work, based on a N ‐ n ‐propylacrylamide (NNPAM) core with N ‐3‐(dimethylamino)propylmethacrylamide (DAPMA) as a comonomer, a series of core‐shell microgels with shells from NNPAM and N ‐(3‐aminopropyl)methacrylamide hydrochloride (APMH) are...

In an in‐depth study of the mechanism of cation release from carboxymethyl cellulose hydrogels synthesized through Schiff base reaction, we analyze the differences in the release kinetics of potassium, calcium, and iron cations with Peleg model at pH values of pH 3.5 and pH 8.5 using ICP‐OES (inductively coupled plasma optical emission spectroscopy...

Using enzymes as catalysts in biochemical processes requires to bring them into close contact with the substrates to be processed. For oil-soluble substrates and water soluble enzymes this might be achieved by bringing the water and oil phase in a bicontinuous microemulsion into close contact. In this contribution we review two possible scenarios o...

The saponin β\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\beta$$\end{document}-aescin is well known for its self-aggregation above the critical micelle concentratio...

In the context of a more sustainable economy, bio-surfactants become increasingly important, due to their independence of petrol-based chemistry, their usually mild synthesis conditions, and in certain cases their pharmacological activity. We have recently discussed self-assembly studies in binary systems of bio-surfactants of microbial origin, or...

Understanding the mechanical behavior of biological membranes is of paramount importance in cell biophysics and in developing new biomaterials for medicine. In this study, we delve into the mechanical impact of β-escin, commonly referred to as escin, a naturally occurring biosurfactant derived from the seeds of the horse chestnut tree. To examine t...

Using artificially reconstituted membranes based on structurally liquidlike phospholipids, we have performed an experimental study on the mechanical impact of the saponin β-aescin, aka escin, a natural biosurfactant extracted from the seeds of the horse chestnut tree Aesculus hippocastanum. The paper focusses on the modulable interaction of escin w...

Hydrothermal carbonization (HTC) is an efficient thermochemical method for the conversion of organic feedstock to carbonaceous solids. HTC of different saccharides is known to produce microspheres (MS) with mostly Gaussian size distribution, which are utilized as functional materials in various applications, both as pristine MS and as a precursor f...

Biodegradable hydrogels have great potential in agriculture. In this study, hydrogel prototypes of biodegradable slow-release fertilizers were formulated by a Schiff base reaction between dialdehyde carboxymethyl cellulose and gelatin. The release behavior of iron cations from these carboxymethyl cellulose-based hydrogels with different degrees of...

In this study, the interplay among the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) as a model membrane, the nonsteroidal anti-inflammatory drug naproxen, and the saponin β-aescin are investigated. The naproxen amount was fixed to 10 mol %, and the saponin amount varies from 0.0 to 1.0 mol%. Both substances are common ingredients...

In this work, a continuous flow setup for in situ investigation of microgel growth with small-angle X-ray scattering (SAXS) is established. Poly(N-n-propylacrylamide) (PNNPAM) and poly(N-isopropylacrylamide) (PNIPAM) microgels are synthesized in H2O at different residence times inside a continuous flow reactor. The microgels are investigated by in...

Recent studies of self-assembly in binary systems of bio-surfactants, either of microbial origin or saponins extracted from plants, are reviewed. Saponins in water reported in the first section include aescin, glycyrrhizin, and quillaja saponins, while rhamnolipids are discussed in the second section on microbial surfactants. Studies of surface act...

A colloidal synthesis’ proof-of-concept based on the Bligh–Dyer emulsion inversion method was designed for integrating into lipid nanoparticles (LNPs) cell-permeating DNA antisense oligonucleotides (ASOs), also known as GapmeRs (GRs), for mRNA interference. The GR@LNPs were formulated to target brain border-associated macrophages (BAMs) as a centra...

Xanthan gum is a polysaccharide that is widely used as a thickening agent in numerous food, cosmetic, and technical applications. Therefore, the knowledge of the molecular interplay that builds up and stabilizes water-binding networks is crucial for the optimization of xanthan thickening performance. Using atomic force microscopy, rheometry, and in...

In this work, palladium-loaded smart membranes made by UV cross-linking of thermoresponsive microgels are prepared to obtain a reusable, catalytically active material which can, for example, be implemented in chemical reactors. The membranes are examined with respect to their coverage of a supporting mesh via atomic force microscopy measurements. F...

Certain EO/PO-triblock polymers can form densely packed spherical micelles and cubic liquid crystalline phases at high concentrations. Usually these are highly elastic and inherently stable gels. This article deals with the effect of various additives on the phase behavior of an EO/PO-triblock polymer, in particular on the existence range of the cu...

Meanwhile for more than three decades smart micro‐ and nanogels are studied and the number of publications in this area of research is steadily growing. This year to date (May 2021) already more than 400 articles were published on this topic. In the study of such colloidal gels, the most important techniques besides microscopy are scattering techni...

While core-shell microgels have been intensively studied in their fully synthesized state, the formation mechanism of the shell has not been completely understood. Such insight is decisive for a customization of microgel properties for applications. In this work, microgels based on a N-isopropylmethacrylamide (NiPMAM) core and a N-n-propylacrylamid...

The commercial availability of natural surfactants, e.g., alkyl-oligoglucosides and the solubilization of plant and food grade oils extends the field of applications for microemulsions. To study potential effects of the confinement on the structure and dynamics inside a microemulsion, neutron reflectometry and neutron spin echo spectroscopy under g...

Front Cover: In article number 2200045, Thomas Hellweg and co‐workers describe the preparation of a variety of PNNPAM‐based microgels copolymerized with methacrylic acid and loaded with monodisperse catalytically active palladium nanoparticles. The copolymerized methacrylic acid leads to interesting pH‐ and thermoresponsive properties of the gel pa...

In this work, we present core-shell microgels with tailor-made architecture and properties for the incorporation of palladium nanoparticles. The microgel core consists of poly-N-isopropylacrylamide (PNIPAM) copolymerized with methacrylic acid (MAc) as anchor point for the incorporation of palladium nanoparticles. The microgel shell is prepared by c...

In the present article, we use an improved Flory–Rehner theory to describe the swellingbehavior of copolymer microgels, where the interaction parameter is modeled by a Hill-like equationfor a cooperative thermotropic transition. This description leads to very good fits of the swellingcurves of the copolymer microgels at different comonomer contents...

Poly‐N‐n‐propylacrylamide (PNNPAM) based microgels with embedded Pd‐nanoparticles are synthesized with varying amounts (5‐25 mol%) of methacrylic acid (MAc) comonomer. The microgels are characterized to investigate the influence of the comonomer content on catalytic activity of the hybrid particles. Since the acidity changes significantly upon copo...

Cutting‐edge biomedical applications require increasingly complex and fastidious cell systems, for example, various classes of primary or stem cells. Their cultivation, however, still differs little from 30 years ago. This especially applies to the use of indiscriminative proteases for nonspecific cell detachment. A far more gentle alternative chan...

Polyacrylamide-based waterborne microgels were prepared with copolymerized carboxylic acid and tertiary amine moieties. The colloidal gels were loaded with palladium nanoparticles and utilized for the Suzuki-Miyaura cross-coupling of amino acids and peptides. The thermoresponsive properties of the prepared microgels were characterized by means of p...

The description of gel swelling by Flory and Rehner using the original Flory–Huggins interaction parameter for the polymer–solvent interaction cannot be applied to most smart microgels. Here, we compare descriptions of the swelling curves of such microgels using series expansions of the Flory–Huggins parameter $$\chi$$ χ with the results of Hill-li...

In this study we show a possibility to produce thermoresponsive, free-standing microgel membranes based on N-isopropylacrylamide (NIPAM) and the UV-sensitive comonomer 2-hydroxy-4-(methacryloyloxy)benzophenone (HMABP). To influence the final network structure and functionality of the membranes, we use different cross-linkers in the microgel synthes...

Filtration through membranes with nanopores is typically associated with high transmembrane pressures and high energy consumption. This problem can be addressed by reducing the respective membrane thickness. Here, a simple procedure is described to prepare ultrathin membranes based on protein nanopores, which exhibit excellent water permeance, two...

Phosphatidylglycerols represent a large share of the lipids in the plasmamembrane of procaryotes. Therefore, this study investigates the role of charged lipids in the plasma membrane with respect to the interaction of the antiviral saponin glycyrrhizin with such membranes. Glycyrrhizin is a natural triterpenic-based surfactant found in licorice. Ve...

Mol. Nutr. Food Res. 2021, 65, 202100200 DOI: 10.1002/mnfr.202100200 An integral physicochemical and functional approach demonstrated that pepsin gliadin digest forms spontaneously amyloid-type nanostructures whose interaction with the Caco-2 enterocyte cellular model induces the expression of selected mRNAs involved in the activation of immune cel...

In this study we use poly(N-isopropylacrylamide) (PNIPAM) based copolymer microgels to create free-standing, transferable, thermoresponsive membranes. The microgels are synthesized by copolymerization of NIPAM with 2-hydroxy-4-(methacryloyloxy)–benzophenone (HMABP) and spin-coated on Si wafers. After subsequent cross-linking by UV-irradiation, the...

Scope Proteolysis-resistant gliadin peptides are intensely investigated in biomedical research related to Celiac Disease and gluten-related disorders. Herein, the first integrated supramolecular investigation of pepsin-digested gliadin peptides, p-gliadin, is presented in combination with its functional behavior in Caco-2 cell line. Methods and re...

The European Spallation Source (ESS), which is under construction in Lund (Sweden), will be the leading and most brilliant neutron source and aims at starting user operation at the end of 2023. Among others, two small angle neutron scattering (SANS) machines will be operated. Due to the high brilliance of the source, it is important to minimize the...

In the present study, smart responsive microgels are synthesized from a series of alternative monomers, which are less common in micro‐ and nanogel research. Their swelling behavior is studied by means of photon correlation spectroscopy and Fourier transform infrared spectroscopy. In addition, these monomers are used to make copolymer microgels. In...

CBD is a promising candidate for treatment of many diseases and plays a major role in the growing trend to produce high-end drugs from natural, renewable resources. In the present work, we demonstrate a way to incorporate the anti-inflammatory drug CBD into smart microgel particles. The copolymer microgels that we chose as carrier systems exhibit a...

The FlexiProb project is a joint effort of three soft matter groups at the Universities of Bielefeld, Darmstadt, and Munich with scientific support from the European Spallation Source (ESS), the small-K advanced diffractometer (SKADI) beamline development group of the Jülich Centre for Neutron Science (JCNS), and the Heinz Maier-Leibnitz Zentrum (M...

As part of the development of the new European Spallation Source (ESS) in Lund (Sweden), which will provide the most brilliant neutron beams worldwide, it is necessary to provide different sample environments with which the potential of the new source can be exploited as soon as possible from the start of operation. The overarching goal of the proj...

A full quantitative description of the swelling of smart microgels is still problematic in many cases. The original approach of Flory and Huggins for the monomer–solvent interaction parameter χ cannot be applied to some microgels. The reason for this obviously is that the cross-linking enhances the cooperativity of the volume phase transitions, sin...

Gliadin is a protein in wheat gluten that is not fully degraded during human digestion. The remaining large undigested peptides produce diverse diseases affecting around 5% of the general population. The complicated relationship between food properties, behavior during digestion, and their contribution to human nutrition and health are not well un...

While cationic microgels are potentially useful for the transfection or transformation of cells, their synthesis has certain drawbacks regarding size, polydispersity, yield, and incorporation of the cationic comonomers. In this work, a range of poly(N-isopropylacrylamide) (PNIPAM) microgels with different amounts of the primary amine N-(3-aminoprop...

In this study, we investigate the influence of the block copolymer architecture on the bending elasticity of polymer-rich lamellar phases. In detail, we study the polymer-rich system water/o-xylene/Pluronic triblock copolymer/C 8 TAB and change the polymer while keeping the mass ratios constant. We use neutron spin echo measurements (NSE) to determ...

In this work, we present a combination of a continuous flow reactor with in situ monitoring of the monomer conversion in a precipitation polymerization. The flow reactor is equipped with a preheating area for the synthesis of thermoresponsive microgels, based on N-isopropylacrylamide (NIPAM). The reaction progress is monitored with in situ FTIR spe...

The manifold applications of porous materials, such as in storage, separation, and catalysis, have led to an enormous interest in their cost-efficient preparation. A promising strategy to obtain porous materials with adjustable pore size and morphology is to use templates exhibiting the appropriate nanostructure. In this study, close-packed polysty...

Poly(N-isopropylacrylamide) (pNIPAM) based copolymer microgels were used to create free-standing, transferable, thermoresponsive membranes. The microgels were synthesized by copolymerization of NIPAM with N-benzylhydrylacrylamide (NBHAM). Monolayers of these colloidal gels were subsequently cross-linked using an electron gun leading to the formatio...

The saponin β-aescin from the seed extract of the horse chestnut tree Aesculus hippocastanum has demonstrated a beneficial role in clinical therapy which is in part related to its strong interaction with biological membranes. In this context the present work investigates the self-assembly of nm-sized discoidal lipid nanoparticles composed of β-aesc...

Inspired by the path followed by Matthias Ballauff over the past 20 years, the development of thermosensitive core-shell microgel structures is reviewed. Different chemical approaches, from hard nanoparticle cores to double stimuli-responsive microgels have been devised and successfully implemented by many different groups. Some of the rich variety...

The peculiar linear temperature-dependent swelling of core-shell microgels has been conjectured to be linked to the core-shell architecture combining materials of different transition temperatures. Here the structure of pNIPMAM-core and pNNPAM-shell microgels in water is studied as a function of temperature using small-angle neutron scattering with...

Mild reaction conditions are highly desirable for bio‐orthogonal side chain derivatizations of amino acids, peptides or proteins due to the sensitivity of these substrates. Transition metal catalysed cross‐couplings such as Suzuki–Miyaura reactions are highly versatile, but usually require unfavourable reaction conditions, in particular, when appli...

We study the complex mixture of a polyethylene oxide-b-polypropylene oxide-b-polyethylene oxide triblock copolymer (Pluronic F127) with ionic liquid (IL) and Li-salt, which is potentially interesting as an electrolyte system with decoupled mechanical and ion-transport properties. Small-angle X-ray scattering (SAXS) and differential scanning calorim...

We study the complex mixture of a polyethylene oxide-b-polypropylene oxide-b-polyethylene oxide triblock copolymer (Pluronic F127) with ionic liquid (IL) and Li-salt, which is potentially interesting as an electrolyte system with decoupled mechanical and ion transport properties. Small-angle X-ray scattering (SAXS) and differential scanning calorim...

In a recent publication [Bergmann et al. Phys. Chem. Chem. Phys., 2018, 20, 5074-5083] we presented a method which enables to investigate the morphology of microgels by superresolution fluorescence microscopy. Here is, method is applied to three microgels species, based on N-isopropylmethacrylamide (NIPMAM), N-n-propylacrylamide (NNPAM) and N-n-pro...

Inspired by the path followed by Matthias Ballauff over the past 20 years, the development of thermosensitive core-shell microgel structures is reviewed. Different chemical structures, from hard nanoparticle cores to double stimuli-responsive microgels have been devised and successfully implemented by many different groups. Some of the rich variety...

In the present study, we show how acrylamide-based microgels can be employed for the uptake and release of the drug β-aescin, a widely used natural product with a variety of pharmacological effects. We show how aescin is incorporated into the microgel particles. It has an important influence on the structure of the microgels, by reducing their natu...

Responsive core-shell microgels are promising systems for a stabilization of Pd nanoparticles and control of their catalytic activity. Here, poly-N-n-propylacrylamide (PNNPAM) was copolymerized with methacrylic acid to make the core micorgels and subsequently coated with an additional, acid-free poly-N-isopropylmethacrylamide (PNIPMAM) shell. Both...

β -aescin is a versatile biosurfactant extracted from the seeds of the horse chestnut tree Aesculus hippocastanum with anti-cancer potential and is commonly used in the food and pharmaceutical and cosmetic industries. In this article, wide-angle X-ray scattering (WAXS) is used in order to study the modifications of the structural parameters at the...

In this study, we investigated the conversion of lipid bicelles into vesicles in case of a system composed of the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and the saponin glycyrrhizin in the presence of sucrose. Glycyrrhizin is a bio-surfactant present in the licorice root and posses a triterpenic hydrophobic backbone and a h...

The radial density profile of deuterated poly(N,n-propyl acrylamide) shell monomers within core-shell microgels has been studied by small angle neutron scattering in order to shed light on the origin of their linear thermally-induced swelling. The poly(N-isopropyl methacrylamide) core monomers have been contrast-matched by the H2O/D2O solvent mixtu...

This review discusses recent progress in physicochemical understanding of the action of the saponin β-aescin (also called β-escin), the biologically active component in the seeds of the horse chestnut tree Aesculus hippocastanum. β-Aescin is used in pharmacological and cosmetic applications showing strong surface activity. In this review, we outlin...

We investigate the internal morphology of smart core-shell microgels by super-resolution fluorescence microscopy exploiting a combination of 3D single molecule localization and structured illumination microscopy utilizing freely diffusing fluorescent dyes. This approach does not require any direct chemical labeling and does not perturb the network...

The investigation of the response kinetics of smart colloidal microgel films is crucial for their optimization to enable advanced applications. We study the classical thermo-responsive microgel model system N-isopropylacrylamide (NIPAM) cross-linked with N,N’-methylenebisacrylamide (BIS). Without the typically used polyelectrolyte coating of the su...

Mixtures of the phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and the saponin β-aescin spontaneously form monodisperse, bilayered discoidal micelles (also known as “bicelles” or “nanodisks”) in aqueous solution. Such bicelles form below the melting temperature of DMPC when the phospholipids are in the rigid Lβ′ state and are precu...

The peculiar linear temperature-dependent swelling of core-shell microgels has been conjectured to be linked to the core-shell architecture combining materials of different transition temperatures. Here the structure of pNIPMAM-core and pNNPAM-shell microgels in water is studied as a function of temperature using small-angle neutron scattering with...

Depending on the linker length between the V H and the V L domain, single-chain Fv (scFv) antibody fragments form monomers, dimers (diabodies) or higher oligomers. We aimed at generating a diabody of the anti-MET antibody 3H3 to use it as crystallization chaperone to promote crystallization of the MET ectodomain through the introduction of a pre-fo...

The present study focuses on the development of multiresponsive core-shell microgels and the manipulation of their swelling properties by copolymerization of different acrylamides—especially N-isopropylacrylamide (NIPAM), N-isopropylmethacrylamide (NIPMAM), and NNPAM—and acrylic acid. We use atomic force microscopy for the dry-state characterizatio...

Thermo- and pH-responsive copolymer microgels were obtained by surfactant-assisted precipitation poylmerization of N-isopropylacrylamide (NiPAM) and acrylic acid (AAc). The surfactants used were sodium dodecylsulfate (SDS), dodecyltrimethylammonium bromide (DTAB) and the nonionic n-octyl-b-D-glucopyranoside (C⁸G¹). We investigate the influence of t...

Aureochromes (AUREO) act as blue-light photoreceptors in algae. They consist of a light-, oxygen-, voltage-sensitive (LOV) domain and a DNA-binding basic region/leucine zipper. Illumination of the flavin cofactor in LOV leads to the formation of an adduct, followed by global structural changes. Here, we first applied UV/vis spectroscopy to characte...

Electronic Supplementary Materials for the article: "Self-Assembly of the Bio-Surfactant Aescin in Solution: A Small-Angle X-Ray Scattering and Fluorescence Study" DOI: 10.3390/colloids3020047

This work investigates the temperature-dependent micelle formation as well as the micellar structure of the saponin aescin. The critical micelle concentration ( c m c ) of aescin is determined from the concentration-dependent autofluorescence (AF) of aescin. Values between c m c aescin , AF (10 ∘ C) = 0.38 ± 0.09 mM and c m c aescin , AF (50 ∘ C) =...