A5074671038- Advanced Polymer Synthesis and Characterization
- Block Copolymer Self-Assembly
- Hydrogels: synthesis, properties, applications
- Surfactants and Colloidal Systems
- Polymer Surface Interaction Studies
- Material Dynamics and Properties
- Rheology and Fluid Dynamics Studies
- Advanced Sensor and Energy Harvesting Materials
- Polymer Nanocomposites and Properties
- Theoretical and Computational Physics
- Electrostatics and Colloid Interactions
- Organic Electronics and Photovoltaics
- NMR spectroscopy and applications
- Nanoparticle-Based Drug Delivery
- Polymer crystallization and properties
- Fluid Dynamics and Thin Films
- Force Microscopy Techniques and Applications
- Synthesis and properties of polymers
- Polymer composites and self-healing
- Silicone and Siloxane Chemistry
- Dendrimers and Hyperbranched Polymers
- Liquid Crystal Research Advancements
- Microfluidic and Capillary Electrophoresis Applications
- Analytical Chemistry and Sensors
- biodegradable polymer synthesis and properties
Technical University of Munich
2016-2025
Institut für Technische und Angewandte Physik (Germany)
2014-2020
Max Planck Computing and Data Facility
2016-2020
Democritus University of Thrace
2018
University of Science and Technology of China
2012
Roskilde University
1994-2008
Leibniz Institute of Polymer Research
2008
TU Dresden
2008
Cornell University
2003-2008
Leipzig University
1999-2006
Defined aggregates of polymers such as polymeric micelles are great importance in the development pharmaceutical formulations. The amount drug that can be formulated by a delivery system is an important issue, and most systems suffer from their relatively low drug-loading capacity. However, loading capacities increase, i.e., promoted good drug-polymer interactions, may affect morphology stability micellar system. We investigated this effect prominent with very high capacity for hydrophobic...
Modulating the thermo-responsive behaviour of poly(sulfobetaine methacrylates) whereby small structural changes cause big effects but show little logic.
‘‘Living’’ anionic polymerization offers a readily feasible preparation of very well-controlled homo- or copolymers in wide range molar masses and chemical structures. Such samples are vital experimental polymer physics the technique presented here self-sufficiency with such samples. The performed under inert atmosphere is here. components setup described detail. Purification procedures for glassware chemicals specific polymerizations given. Illustrative examples results presented.
Grazing-incidence small-angle X-ray or neutron scattering of thin polymer films reveals information about the ordering and preferential orientations phase-separated microdomains within films. The grazing-incidence geometry enhances surface sensitivity; however, has to be treated framework distorted-wave Born approximation. In this work, case with lamellar mesostructure is studied, where orientation lamellae either perpendicular parallel film interfaces. For lamellae, Bragg rods are found,...
We have studied the thermal behavior of amphiphilic, symmetric triblock copolymers having short, deuterated polystyrene (PS) end blocks and a large poly(N-isopropylacrylamide) (PNIPAM) middle block exhibiting lower critical solution temperature (LCST) in aqueous solution. A wide range concentrations (0.1−300 mg/mL) is investigated using number analytical methods such as fluorescence correlation spectroscopy (FCS), turbidimetry, dynamic light scattering (DLS), small-angle neutron (SANS),...
This feature article reviews our recent advancements on the synthesis, phase behavior, and micellar structures of diblock copolymers consisting oppositely thermoresponsive blocks in aqueous environments. These combine a nonionic block, which shows lower critical solution temperature (LCST) with zwitterionic block that exhibits an upper (UCST). The transition latter class polymers is strongly controlled by its molar mass salt concentration, contrast to rather invariant type II LCST behavior...
The lamellar orientation in supported, thin films of poly(styrene-b-butadiene) (P(S-b-B)) depends on block copolymer molar mass. We have studied from nine samples with masses between 13.9 and 183 kg/mol using grazing-incidence small-angle X-ray scattering (GISAXS) found that low mass the lamellae are parallel to substrate surface, whereas they perpendicular for high masses. For a thick, film, bulk limit is approached; i.e., randomly oriented present. 2D GISAXS images discussed quantitatively...
We have investigated the structural changes in thin films of lamellar poly(styrene-b-butadiene) diblock copolymers during treatment with saturated cyclohexane vapor, a solvent slightly selective for polybutadiene. Using real-time, in-situ grazing-incidence small-angle X-ray scattering (GISAXS), swelling and rearrangement lamellae were time resolution few seconds, underlying processes on molecular level identified. After minutes transient state more well-defined long-range ordered orientation...
Abstract Six new bifunctional bis(trithiocarbonate)s were explored as RAFT agents for synthesizing amphiphilic triblock copolymers ABA and BAB, with hydrophilic “A” blocks made from N ‐isopropylacrylamide hydrophobic “B” styrene. Whereas the extension of poly( ‐isopropylacrylamide) by styrene was not effective, polystyrene macroRAFT provided block efficiently. End group analysis 1 H NMR spectroscopy supported molar mass revealed an unexpected side reaction certain bis(trithiocarbonate)s,...
Abstract The micelle formation of five poly(2‐oxazoline) diblock, triblock and gradient copolymers in water was investigated using fluorescence correlation spectroscopy. polymers were synthesized by consecutive or simultaneous living cationic polymerization 2‐methyl‐2‐oxazoline for the hydrophilic 2‐nonyl‐2‐oxazoline hydrophobic polymer segments. Fractions fluorescence‐labeled at termini with TRITC FCS measurements. hydrodynamic radii solubilized unimers aggregates (micelles) determined a...
The phase separation mechanism in semidilute aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions is investigated with small-angle neutron scattering (SANS). nature of the transition probed static SANS measurements and time-dependent after a temperature jump. observed critical exponents describing dependence Ornstein-Zernike amplitude correlation length are smaller than values from mean-field theory. Time-dependent show that specific surface decreases increasing time jump above transition....
For aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions, a structural instability leads to the collapse and aggregation of macromolecules at temperature-induced demixing transition. The accompanying cooperative dehydration PNIPAM chains is known play crucial role in this phase separation. We elucidate impact partial on volume changes related separation dilute concentrated solutions. Quasi-elastic neutron scattering enables us directly follow isotropic jump diffusion behavior hydration...
The reorientation of lamellae and the dependence lamellar spacing,
Octa-OH-functional POSS has been incorporated into a model polyurethane elastomer as comparatively massive and notionally "robust" 3-dimensional cross-linking core. The effects of this moiety on the morphology molecular dynamics system are studied over range size time scales. Microscopy, scattering, spectroscopic, thermal, dielectric techniques, in agreement with each other, show that covalent inclusion particles restricts microphase separation, inhibits formation hard-block domains,...
Dissipative particle dynamics was applied to simulate solvent vapor annealing in films of cylinder-forming diblock copolymers. Our simulations reveal a wide range conditions, under which the vertical domain orientation is promoted by fast evaporation. First, order-to-disorder transition must be induced upon swelling film. This condition ensures independence structure formation during drying on history, i.e., preparation conditions. Second, weak segregation regime has achievable evaporation...
A novel thermoresponsive gelator of (B-co-C)-b-A-b-(B-co-C) topology, comprising a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) weak polyelectrolyte as central block, end-capped by thermosensitive poly(triethylene glycol methyl ether methacrylate/n-butyl [P(TEGMA-co-nBuMA)] random copolymers, was designed and explored in aqueous media. The main target this design to control the dynamics stickers temperature create an injectable hydrogel that behaves gel at low strong physiological...
A 2-fold thermoresponsive diblock copolymer PSPP430-b-PNIPAM200 consisting of a zwitterionic polysulfobetaine (PSPP) block and nonionic poly(N-isopropylacrylamide) (PNIPAM) is prepared by successive RAFT polymerizations. In aqueous solution, the corresponding homopolymers PSPP PNIPAM feature both upper lower critical solution temperature (UCST LCST) behavior, respectively. The exhibits thermally induced “schizophrenic” aggregation behavior in solutions. Moreover, ion sensitivity cloud point...
The swelling and phase transition behavior upon increasing temperature of a doubly thermoresponsive diblock copolymer thin film in steps above the characteristic cloud points (CPs) blocks is studied. An upper critical solution (UCST)-type zwitterionic poly(sulfobetaine), poly(N,N-dimethyl-N-(3-methacrylamidopropyl)-ammoniopropane sulfonate) (PSPP, CPUCST = 31.5 °C), combined with lower (LCST)-type nonionic poly(N-isopropyl-/methacrylamide) (PNIPMAM, CPLCST 49.5 °C) block. Using...
Poly(N-isopropylmethacrylamide) (PNIPMAM) is a thermoresponsive polymer, exhibiting lower critical solution temperature (LCST) behavior in an aqueous solution. We investigate the temperature-dependent phase of PNIPMAM solutions D2O using turbidimetry, differential scanning calorimetry (DSC), small-angle and very small angle neutron scattering (SANS VSANS), Raman spectroscopy, covering large concentration range, compare results from with findings its analogue poly(N-isopropylacrylamide)...
Biodegradable self-healing hydrogels are highly desirable materials for therapeutic systems, reusable devices, and intelligent cell/drug carriers. Many research efforts focus on additional functionalities of through physical or chemical strategies/designs. Herein, N-[3-(4-hydroxyphenyl)propanamido] chitosan a difunctional Pluronic-F127 crosslinker (DF-PF) were synthesized reacted to form the phenolic-chitosan hydrogel (CPF) with high water content (96.5 wt%). Coherent small-angle X-ray...
Abstract Sets of the nonionic polymers poly( N -vinyl isobutyramide) (pNVIBAm) and -isopropyl methacrylamide) (pNIPMAm) are synthesized by radical polymerization covering molar mass range from about 20,000 to 150,000 kg mol −1 , their thermoresponsive solvent-responsive behaviors in aqueous solution studied. Both feature a lower critical temperature (LCST) apparently rare so-called type II, as characteristic for well-studied analogue acrylamide) (pNIPAm). Moreover, analogy pNIPAm, both...
Abstract Soft materials are usually defined as made of mesoscopic entities, often self-organised, sensitive to thermal fluctuations and weak perturbations. Archetypal examples colloids, polymers, amphiphiles, liquid crystals, foams. The importance soft in everyday commodity products, well technological applications, is enormous, controlling or improving their properties the focus many efforts. From a fundamental perspective, possibility manipulating material properties, by tuning...
Poly(N-isopropylacrylamide) (PNIPAM) is known for exhibiting lower critical solution temperature behavior in water. A structural isomer of PNIPAM, the likewise LCST-type polymer poly(N-vinylisobutyramide) (PNVIBAM), compared to PNIPAM a thin film with respect their swelling behaviors and water uptake kinetics humid atmosphere. Based on spectral reflectance, Fourier-transform infrared (FT-IR) spectroscopy, time-of-flight neutron reflectometry, amount uptaken its distribution inside films...