6 Materialchemie
Filtern
Dokumenttyp
- Zeitschriftenartikel (131)
- Beitrag zu einem Tagungsband (2)
- Buchkapitel (1)
Sprache
- Englisch (134)
Referierte Publikation
- ja (134) (entfernen)
Schlagworte
- Microplastics (11)
- Broadband dielectric spectroscopy (9)
- DNA (9)
- Dosimetry (7)
- Microplastic (7)
- Nanocomposites (7)
- Radiation damage (7)
- Geant4 (6)
- Geant4-DNA (6)
- Microdosimetry (6)
- TED-GC/MS (6)
- DNA damage (5)
- Ectoine (5)
- LEE (5)
- Simulation (5)
- X-ray scattering (5)
- Atomic force microscopy (4)
- AuNP (4)
- Beta decay (4)
- Brachytherapy (4)
- Cancer treatment (4)
- Discotic Liquid Crystals (4)
- Discotic liquid crystals (4)
- Energy deposit (4)
- Gold Nanoparticles (4)
- Low energy electrons (4)
- MCS (4)
- Monte-Carlo simulation (4)
- NP (4)
- Nanoparticles (4)
- Radiationtherapy (4)
- Radioactive decay (4)
- SSB (4)
- Specific heat spectroscopy (4)
- TOPAS (4)
- TOPAS-nbio (4)
- Advanced calorimetry (3)
- Base damage (3)
- Base loss (3)
- Boehmite (3)
- Direct laser writing (3)
- Ectoin (3)
- Epoxy (3)
- Flash DSC (3)
- G5P (3)
- Intermodulation AFM (3)
- Ionic Liquid Crystals (3)
- Multiphoton lithography (3)
- Nanocomposite (3)
- Neutron scattering (3)
- OH radical (3)
- OH radicals (3)
- Particle scattering (3)
- Polymers of intrinsic microporosity (3)
- Protein (3)
- ROS (3)
- Radical scavenger (3)
- Radiolysis (3)
- Reference material (3)
- SAXS (3)
- ssDNA (3)
- Adsorption (2)
- Aluminium oxide hydroxide (2)
- Analysis (2)
- Antibacterial (2)
- Beta particle (2)
- Bio-SAXS (2)
- Boson peak (2)
- Clustered nanoparticles (2)
- Composites (2)
- Cosolute (2)
- DMSO (2)
- DNA radiation damage (2)
- Dielectric spectroscopy (2)
- Direct damage (2)
- Dissociative electron attachment (DEA) (2)
- Dissociative electron transfer (DET) (2)
- Double-strand break (DSB) (2)
- Electrolyte membrane (2)
- Electrospinning (2)
- Epoxy nanocomposites (2)
- Fast scanning calorimetry (2)
- Friction (2)
- GVP (2)
- Gamma ray (2)
- Gas separation membranes (2)
- Glass transition temperature (2)
- Graphene oxide (2)
- Hydrated DNA (2)
- Hydrated electron (2)
- Hydration shell (2)
- Hydroxyectoine (2)
- Hydroxyl radical (2)
- Indirect damage (2)
- Interphase (2)
- Ionization (2)
- Ionizing radiation damage (2)
- Lead ions (2)
- Liquid crystals (2)
- Livermore model (2)
- Mechanical properties (2)
- Micropatterning (2)
- Monte-Carlo simulations (2)
- NAP-XPS (2)
- Nanoparticle (2)
- Near ambient pressure xray photo electron spectroscopy (2)
- Net-ionization reaction (2)
- Neutron Scattering (2)
- OH radical scavenger (2)
- Particle scattering simulations (2)
- Penelope model (2)
- Polydopamine (2)
- Polymer composites (2)
- Polymer of intrinsic microporosity (2)
- Polymers (2)
- Polymers of Intrinsic Microporosity (2)
- Polynorbornenes (2)
- Polyurethane (2)
- Polyvinyl alcohol (2)
- Prehydrated electron (2)
- Protein unfolding (2)
- Quasi-direct damage (2)
- Quasielastic neutron scattering (2)
- Radiation therapy (2)
- Radical (2)
- Raman spectroscopy (2)
- Reactive oxygen species (2)
- Rhodamine B (2)
- Rigid amorphous fraction (2)
- Rosin (2)
- SZ2080 negative photo-resist (2)
- Single-strand break (SSB) (2)
- Single-stranded DNA-binding proteins (2)
- Soil (2)
- Solution doping (2)
- Synthesis (2)
- TGA (2)
- Thermoplastics (2)
- Thin films (2)
- Thin polymer films (2)
- Tire wear (2)
- Ultra thin polymer films (2)
- XPS (2)
- Xray (2)
- Xray photo electron spectrocopy (2)
- 1H-NMR (1)
- 266nm (1)
- 2PP (1)
- AFM (1)
- AFM force distance curves (1)
- AFM force spectroscopy (1)
- AFM friction analysis (1)
- AFM plastic deformation (1)
- AFM stiffness of interface (1)
- AGE (1)
- APTES (1)
- Abasic site (1)
- Additive manufacturing (1)
- Adsorbed Layer (1)
- Advanced materials (1)
- Agarose gel electrophorese (1)
- Aging (1)
- Aktivkohle (1)
- Alpha (1)
- Amino Acids (1)
- Analytical Chemistry (1)
- Artificial weathering (1)
- Atomic and Molecular Physics and Optics (1)
- Au (1)
- Automation (1)
- BET (1)
- Bacteriophage f1 (1)
- Bbeverages (1)
- Beta elimination (1)
- BioSAXS (1)
- Biodosimetry (1)
- Biologisches Dosimeter (1)
- Biomarker (1)
- Bloch wall (1)
- Blockcopolymer (1)
- Boehmit nanoparticle (1)
- Boehmite nanoparticles (1)
- Bragg peak (1)
- Brilliant Blue R (1)
- Broadband Dielectric Spectrscopy (1)
- Broadband dielectric microscopy (1)
- Buffer (1)
- Bystander effect (1)
- CPD (1)
- Cancer (1)
- Cancer therapy (1)
- Carbon Nanomembranes (1)
- Carbon ions (1)
- Cationic photocuring (1)
- Cell size (1)
- Cells (1)
- Cellulose acetate (1)
- Cellulose nanofibrils (1)
- Cladding-doped fibers (1)
- Co (1)
- Cobalt (1)
- Columnar Liquid Crystal (1)
- Compatible solute (1)
- Compost (1)
- Conductivity (1)
- Confocal microscopy (1)
- Confocal raman imaging (1)
- Coordination polymer (1)
- Corrosion (1)
- Corrosion resistance (1)
- Counterions (1)
- Covalent Organic frameworks (1)
- Crosslink density control (1)
- Crosslinking (1)
- Crosslinking density (1)
- Cryo milling (1)
- Curie temperature (1)
- Cy3 (1)
- Cycloaliphatic epoxy oligosiloxane (1)
- DFT calculations (1)
- DFT calculations of Raman spectra (1)
- DNA Dosimeter (1)
- DNA base damage (1)
- DNA based data storage (1)
- DNA data storage (1)
- DNA degradation (1)
- DNA long term storage (1)
- DNA melting temperature (1)
- DNA protection (1)
- DNA reference material (1)
- DNA stability (1)
- DNA strand-break (1)
- DNA vortexing (1)
- DSB (1)
- DSC (1)
- Damping factor (1)
- Data analysis (1)
- Degradation (1)
- Degradation signatures (1)
- Density separation (1)
- Differential scanning calorimetry (1)
- Direct laser interference patterning (1)
- Domain wall (1)
- Dry DNA (1)
- Dye-doped fiber (1)
- Dynamic heterogeneity (1)
- ESCA (1)
- Earthworms (1)
- Ectoine DNA protection (1)
- Ectoine UV absorption (1)
- Ectoine hydration (1)
- Ectoine-DNA binding (1)
- Elastic membrane (1)
- Electrical conductivity (1)
- Electron microscopy (1)
- Electron tomography (1)
- Electrons (1)
- Electrospun nanocomposite fiber (1)
- Energy dependent XPS (1)
- Epoxy conversion degree (1)
- Estrogenic activity of plastic nanoparticles (1)
- Exchange interaction (1)
- Exchange length (1)
- Excited states (1)
- Exploratory analysis (1)
- FLASH effect (1)
- FTIR (1)
- Fabrication parameters (1)
- Fast Scanning Calorimetry (1)
- Fast scanning calormetry (1)
- Fe (1)
- Femtosecond laser (1)
- Fenton Reaction (1)
- Fermi resonance (1)
- Ferromagnetism (1)
- Filter crucible (1)
- Flexible crystals (1)
- Fluorescence (1)
- Fluorescent optical fiber (1)
- Fluorescent optical fibers (1)
- Fluoropolymers (1)
- Force-distance-curve (1)
- Freezing (1)
- Fuell cells (1)
- Functionalization (1)
- Gamma (1)
- Gas sensors (1)
- Gel electrophoresis (1)
- Gene five protein (1)
- Glass transition (1)
- Grafting (1)
- H2O2 (1)
- HPLC (1)
- Hairpin (1)
- Halloysite nanotubes (1)
- Hierarchical structures (1)
- Highly permeably polynorbornenes (1)
- Humidity (1)
- Hydroxyl radicals (1)
- IR (1)
- In-situ polymerization (1)
- Inelastic neutron scattering (1)
- Infrared nano AFM (1)
- Instrumentation (1)
- Interlaboratory comparability (1)
- Interlaboratory comparison (1)
- Intermodulation (1)
- Intermodulation-AFM (1)
- Interpenetrating polymer network (1)
- Ion beam therapy (1)
- Ionic liquid crystal (1)
- Ionic liquid crystalls (1)
- Ionic liquid crystals (1)
- Ionisation (1)
- Iron (1)
- Irreversible adsorption (1)
- Knufia petricola (1)
- LC-UV (1)
- LET (1)
- LL equation (1)
- LLG (1)
- Landau Lifshitz Gilbert equation (1)
- Landau Lifshitz equation (1)
- Landau de-Gennes analysis (1)
- Laser direct writing (1)
- Laser-induced periodic surface structures (LIPSS) (1)
- Lignin (1)
- Liquid Crystals (1)
- MCC (1)
- MCNP (1)
- MOUSE (1)
- MRT (1)
- MWCNT (1)
- Magnet coupling (1)
- Magnetic Nanoparticles (1)
- Magnetic anisotropy (1)
- Magnetic interacion (1)
- Magnetic moment (1)
- Magnetization dynamics (1)
- Mass spectrometry (1)
- Material chemistry (1)
- McSAS3 (1)
- Mechanical flexibility (1)
- Mechanical property (1)
- Mechanical stress (1)
- Membranes (1)
- Metal ions (1)
- Metal oxides (1)
- Methodology (1)
- Methoxytrimethlsilane (1)
- Methyl group rotation (1)
- Microfabrication (1)
- Micromagnetism (1)
- Microplastic fibers (1)
- Mild steel (1)
- Modelling (1)
- Modulus (1)
- Moisture (1)
- Molecular beacon (1)
- Molecular mobility (1)
- Monitoring (1)
- Multi photon lithography (1)
- Mussel-inspired materials (1)
- NIR spectroscopy (1)
- Nanocomposite fibers (1)
- Nanoconfinement (1)
- Nanodosimetry (1)
- Nanomaterials (1)
- Nanomechanical charecteisation (1)
- Nanomechanical properties (1)
- Nanomechanics (1)
- Nanoplastics (1)
- Nanopores (1)
- Nanopropous materials (1)
- Nanosafety (1)
- Nanostructure quantification (1)
- Neel wall (1)
- Ni (1)
- Nickel (1)
- Non-destructive testing (1)
- Nucleobase (1)
- OH (1)
- OH Radical (1)
- OH scavenger (1)
- OOMMF (1)
- Object oriented micromagnetic framework (1)
- Oligonucleotides (1)
- Open data on zenodo (1)
- Optical birefringence (1)
- Organic crystal (1)
- Organic micro-pollutant (1)
- Osmolyte (1)
- Oxidation (1)
- PBS (1)
- PES (1)
- PET (1)
- PFAS (1)
- PIFE (1)
- PMMA (1)
- PUR (1)
- PVDF (1)
- Paramagnetism (1)
- Pharmacy (1)
- Phase transition (1)
- Photons (1)
- Photooxidation (1)
- Physical aging (1)
- Plasma Polymerization (1)
- Plasma Polymers (1)
- Plasma treatments (1)
- Plasmid DNA (1)
- Plastic bottles (1)
- Plastic deformation (1)
- Plastic optical fibers (1)
- Plastic pollution (1)
- Poly(amino phosphodiester) (1)
- Polycarbonate (1)
- Polyethylene colonization (1)
- Polyglycerol (1)
- Polymer analysis/characterization (1)
- Polymer based Nanocomposites (1)
- Polymer blends (1)
- Polymer of intrisic microporosity (1)
- Polymer optical fiber (1)
- Polymer-based nanocomposites (1)
- Polymers with intrinsic microporosity (1)
- Polymethyl methacrylate (1)
- Polynorbornes (1)
- Polyvinyl formaldehyde (1)
- Polyvinyl formaldehyde foam (1)
- Polzmethyl methacrylate (1)
- Position of carboxylate group (1)
- Powdered activated carbon (1)
- Preferential exclusion (1)
- Presolvated electron (1)
- Principle component analysis (1)
- Propolis (1)
- Protein-induced fluorescence enhancement (1)
- Proteins (1)
- Protein–DNA filament (1)
- Pyrolysis (1)
- Quality control (1)
- Quencher (1)
- RAMAN (1)
- RBE (1)
- RNA (1)
- Radiation (1)
- Radiation protection (1)
- Radical Scavenge (1)
- Radical Scavenger (1)
- Radiotherapy (1)
- Raman (1)
- Raman Spectroscopy (1)
- Real-time infrared spectroscopy (1)
- Recycling (1)
- Risk assessment (1)
- River (1)
- Rod-like liquid crystals (1)
- Round Robin (1)
- SBP (1)
- SYBR Gold (1)
- SYBR gold (1)
- Salt (1)
- Sampling (1)
- Sampling techniques (1)
- Sedimentation (1)
- Sedimentation box (SB) (1)
- Semiconductors (1)
- Settling velocity (1)
- Silane (1)
- Single-stranded DNA-binding protein (1)
- Sinking velocity (1)
- Slicers (1)
- Small-angle scattering (1)
- Small-angle xray scattering (1)
- Soft X-ray (1)
- Soil microbial community (1)
- Spectroscopy (1)
- Spin (1)
- Stainless steel (1)
- Steel (1)
- Stochastic Landau Lifshitz Gilbert equation (1)
- Stochastic Landau Lifshitz equation (1)
- Strand break (1)
- Structural precision (1)
- Structure-property relationship (1)
- Structure–property correlation (1)
- Structure–property relationship (1)
- Sulfur cathodes (1)
- Sunscreen (1)
- Superior sorbent (1)
- Superparamagnetism (1)
- Surface (1)
- Surface analysis (1)
- Surface functionalization (1)
- Surface properties (1)
- Surface species (1)
- Suspended organic matter (1)
- Suspended particulate matter (SPM) (1)
- TED-GC-MS (1)
- TEM (1)
- TGA-FTIR (1)
- TGA-MS (1)
- THP(B) (1)
- TPU (1)
- Temeprature scaling (1)
- Temperature effects (1)
- Temperature modulated differential scanning calorimetry (1)
- Tetraethyl orthosilicate (1)
- Thawing (1)
- Therapy (1)
- Thermal analysis (1)
- Thermal desorption mass spectrometry (1)
- Thermal extraction desorption-gas chromatography/mass spectrometry (TED-GC/MS), monitoring (1)
- Thermal extraction-desorption gas chromatography mass spectrometry (1)
- Thermoanalytik (1)
- Thermoset (1)
- Thermoset composition (1)
- Thermosets (1)
- Thin film systems (1)
- Tire Wear (1)
- Tire particles (1)
- Titanium (1)
- Topas (1)
- Topas-MC (1)
- Topas-nBio (1)
- Toxicity (1)
- Trace organic contaminant (1)
- Two-photon polymerization (1)
- UV absorption (1)
- UV irradiation (1)
- UV photons (1)
- UV protection (1)
- UV radiation (1)
- UV-A (1)
- UV-B (1)
- UV-C (1)
- UV-Vis (1)
- Urban (1)
- Van der Waals forces (1)
- Volatiles from thermosets (1)
- Water (1)
- Water samples (1)
- Water treatment (1)
- White light interferometry microscopy (1)
- X-ray microscopy (1)
- X-ray photoelectron spectroscopy (1)
- XCT (1)
- XPS spctroscopy (1)
- Young´s modulus (1)
- Zinc analysis (1)
- Zwitterion (1)
- abasic side (1)
- base loss (1)
- beta particle (1)
- clustered nanoparticles (1)
- dsDNA (1)
- gamma ray (1)
- lN2 (1)
- low energy electrons (1)
- oxidative stress (1)
- pH (1)
- pUC19 (1)
- particle scattering (1)
- radiolysis (1)
- temeprature dependent exchange length (1)
Organisationseinheit der BAM
- 6.6 Physik und chemische Analytik der Polymere (134) (entfernen)
Paper des Monats
- ja (6)
A selected series of dipole functionalized triphenylene-based discotic liquid crystals (DLCs) was synthesized and investigated in a systematic way to reveal the phase behavior and molecular dynamics. The later point is of particular importance to understand the charge transport in such systems which is the key property for their applications such as organic field-effect transistors, solar cells or as nanowires in molecular electronics, and also to tune the properties of DLCs. The mesomorphic properties were studied by polarizing optical microscopy, X-ray diffraction, and differential scanning calorimetry, which were compared to the corresponding unfunctionalized DLC. The molecular dynamics were investigated by a combination of state-of-the-art broadband dielectric spectroscopy (BDS) and advanced calorimetry such as fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). Besides localized fluctuations, surprisingly multiple glassy dynamics were detected for all materials for the first time. Glassy dynamics were proven for both processes unambiguously due to the extraordinary broad frequency range covered. The a1-process is attributed to fluctuations of the alky chains in the intercolumnar space because a polyethylene-like glassy dynamics is observed. This corresponds to a glass transition in a confined three-dimensional space. The a2-process found at temperatures lower than a1-process, is assigned to small scale rotational and/or translational in plane fluctuations of the triphenylene core inside distorted columns. This can be considered as a glass transition in a one-dimensional fluid. Therefore, obtained results are of general importance to understand the glass transition, which is an unsolved problem of condensed matter science.
Thin films (200-7nm) of the asymmetric polymer blend poly(vinyl methyl ether) (PVME)/polystyrene (PS) (25/75wt%) were investigated by broadband dielectric spectroscopy (BDS). Thicker samples ([Formula: see text]37 nm) were measured by crossed electrode capacitors (CEC), where the film is capped between Al-electrodes. For thinner films ([Formula: see text]37 nm) nanostructured capacitors (NSC) were employed, allowing one free surface in the film. The dielectric spectra of the thick films showed three relaxation processes ( [Formula: see text] -, [Formula: see text] - and [Formula: see text] -relaxation), like the bulk, related to PVME fluctuations in local spatial regions with different PS concentrations. The thickness dependence of the [Formula: see text] -process for films measured by CECs proved a spatially heterogeneous structure across the film with a PS-adsorption at the Al-electrodes. On the contrary, for the films measured by NSCs a PVME segregation at the free surface was found, resulting in faster dynamics, compared to the CECs. Moreover, for the thinnest films ([Formula: see text]26 nm) an additional relaxation process was detected. It was assigned to restricted fluctuations of PVME segments within the loosely bounded part of the adsorbed layer, proving that for NSCs a PVME enrichment takes place also at the polymer/substrate interface.
Polyether and -ester urethanes (PU) were exposed to artificial weathering at 40 °C and artificial UV radiation in a weathering chamber. In 3 parallel exposures, humidity was varied between dry, humid, and wet conditions. Material alteration was investigated by various analytical techniques like size exclusion chromatography
(SEC), liquid chromatography-infrared spectroscopy (LC-FTIR), thermal-desorption gas chromatography-mass spectrometry (TD-GC-MS), fluorescence mapping and dynamic mechanical analysis (DMA). Our results show that depending on the weathering conditions, different degradation effects can be observed. By means of SEC an initial strong decrease of the molar masses and a broadening of the mass distributions was found. After a material dependent time span this was followed by a plateau where molar mass changes were less significant. A minor moisture-dependent degradation effect was only found for polyester PU. Fluorescence measurements on two materials revealed an increase in the luminescence intensity upon weathering process reaching a saturation level after about 500 h. The changes in the optical properties observed after different exposure conditions and times were very similar. The TD-GC-MS data showed the fate of the stabilizers and antioxidant in the course of weathering. LC-FTIR measurements revealed a change in peak intensities and the ratio of urethane and carbonyl bands.
Polymers of Intrinsic Microporosity (PIMs) of high performance have developed as materials with a wide application range in gas separation and other energy-related fields. Further optimization and long-term behavior of devices with PIMs require an understanding of the structure-property relationships including physical aging. In this context the glass transi-tion plays a central role, but with conventional thermal analysis a glass transition is usually not detectable for PIMs be-fore their thermal decomposition. Fast scanning calorimetry provides evidence of the glass transition for a series of PIMs, as the time scales responsible for thermal degradation and for the glass transition are decoupled by employing ultrafast heating rates of tens of thousands K s-1. The investigated PIMs were chosen considering the chain rigidity. The estimated glass transition temperatures follow the order of the rigidity of the backbone of the PIMs.
The movement of the macroscopic magnetic moment in ferromagnetic systems can be described by the Landau-Lifshitz (LL) or Landau-Lifshitz-Gilbert (LLG) equation. These equations are strictly valid only at absolute zero temperature. To include temperature effects a stochastic version of the LL or LLG equation for a spin density of one per unit cell can be used instead. To apply the stochastic LL to micromagnetic simulations, where the spin density per unit cell is generally higher, a conversion regarding simulation cell size and temperature has to be established. Based on energetic considerations, a conversion for ferromagnetic bulk and thin film systems is proposed. The conversion is tested in micromagnetic simulations which are performed with the Object Oriented Micromagnetic Framework (OOMMF). The Curie temperatures of bulk Nickel, Cobalt and Iron systems as well as Nickel thin-film systems with thicknesses between 6.3 mono layer (ML) and 31ML are determined from micromagnetic simulations. The results show a good agreement with experimentally determined Curie temperatures of bulk and thin film systems when temperature scaling is performed according to the presented model.
Understanding the interaction between boehmite and epoxy and the formation of their interphases with different mechanical and chemical structures is crucial to predict and optimize the properties of epoxy-boehmite nanocomposites. Probing the interfacial properties with atomic force microscopy (AFM)-based methods, especially particle-matrix long-range interactions, is challenging. This is due to size limitations of various analytical methods in resolving nanoparticles and their interphases, the overlap of interphases, and the effect of buried particles that prevent the accurate interphase property measurement. Here, we develop a layered model system in which the epoxy is cured in contact with a thin layer of hydrothermally synthesized boehmite. Different microscopy methods are employed to evaluate the interfacial properties. With intermodulation atomic force microscopy (ImAFM) and amplitude dependence force spectroscopy (ADFS), which contain information about stiffness, electrostatic, and van der Waals forces, a soft interphase was detected between the epoxy and boehmite. Surface potential maps obtained by scanning Kelvin probe microscopy (SKPM) revealed another interphase about one order of magnitude larger than the mechanical interphase. The AFM-infrared spectroscopy (AFM-IR) technique reveals that the soft interphase consists of unreacted curing agent. The long-range electrical interphase is attributed to the chemical alteration of the bulk epoxy and the formation of new absorption bands.
The TED-GC-MS analysis is a two-step method. A sample is first decomposed in a thermogravimetric analyzer (TGA) and the gaseous decomposition products are then trapped on a solid-phase adsorber. Subsequently, the solid-phase adsorber is analyzed with thermal desorption gas chromatography mass spectrometry (TDU-GC-MS). This method is ideally suited for the analysis of polymers and their degradation processes. Here, a new entirely automated System is introduced which enables high sample throughput and reproducible automated fractioned collection of decomposition products. Strengths and limitations of the system configuration are elaborated via three examples focused on practical challenges in materials analysis and identification: i) separate analysis of the components of a wood-plastic-composite material, ii) quantitative determination of weight concentration of the constituents of a polymer blend and iii) quantitative analysis of model samples of microplastics in suspended particulate matter.
Nanocomposites based on MgAL layered double hydroxides (LDH) and an epoxy resin were prepared and investigated by a combination of complementary methods. As epoxy resin Bisphenol A diglycidyl ether (DGEBA) was used with Diethylenetriamine as curing agent. The LDH was modified with taurine, which acts as an additional crosslinking agent due to its amine groups. The epoxy resin was cured in a presence of the nanofiller, which was added to the system in various concentrations. X-ray scattering, by combination of SAXS and WAXS was used to characterize the morphology of the obtained nanocomposites. These investigations show that the filler is distributed in the matrix as small stacks of ca. 10 layers. The molecular dynamics of the system, as probe for structure, was investigated by broadband dielectric spectroscopy. In addition to the - and -relaxation (dynamic glass transition), characteristic for the unfilled materials, a further process was found which was assigned to localized fluctuations of segments physically adsorbed or chemically bonded to the nanoparticles. The dielectric -relaxation is shifted to higher temperatures for the nanocomposites in comparison to the pure material but depends weakly on the content of nanoparticles. Further, for the first time Flash DSC was employed to a thermosetting system to investigate the glass transition behavior of the nanocomposites. The heating rates were converted in to relaxation rates. For low concentrations of the nanofiller the thermal data overlap more or less with that of the pure epoxy. For higher concentrations the thermal data are shifted significantly to higher temperatures. This is discussed in terms the cooperativity approach to the glass transition.
The antibacterial features of natural pine/spruce rosin are well established, yet the functionality in various thermoplastics has not been surveyed. This work focuses on the processing of industrial grade purified rosin mixed with polyethylene (PE), polypropylene (PP), polylactic acid (PLA), polyamide (PA) and corn starch based biopolymer (CS). Homopolymer masterbatches were extrusion-compounded and melt-spun to form fibres for a wide range of products, such as filters, reinforcements, clothing and medical textiles. Due to the versatile chemical structure of rosin, it was observed compatible with all the selected polymers. In general, the rosin-blended systems were shear-thinning in a molten condition. The doped fibres spun of PE and PP indicated adequate melt-spinning capability and proper mechanical properties in terms of ultimate strength and Young's modulus. The antibacterial response was found dependent on the selected polymer. Especially PE with a 10 wt% rosin content showed significant antibacterial effects against Escherichia coli DH5α and Staphylococcus aureus ATCC 12598 when analysed in the Ringer's solution for 24 h.
In this work, a novel boehmite (BA)-embedded organic/inorganic nanocomposite coating based on cycloaliphatic epoxy oligosiloxane (CEOS) resin was fabricated applying UV-induced cationic polymerization. The main changes of the material behavior caused by the nanofiller were investigated with regard to its photocuring kinetics, thermal stability, and glass transition. The role of the particle surface was of particular interest, thus, unmodified nanoparticles (HP14) and particles modified with p-toluenesulfonic acid (OS1) were incorporated into a CEOS matrix in the concentration range of 1–10 wt.%. Resulting nanocomposites exhibited improved thermal properties, with the glass transition temperature (Tg) being shifted from 30 °C for unfilled CEOS to 54 °C (2 wt.% HP14) and 73 °C (2 wt.% OS1) for filled CEOS. Additionally, TGA analysis showed increased thermal stability of samples filled with nanoparticles. An attractive interaction between boehmite and CEOS matrix influenced the curing. Real-time infrared spectroscopy (RT-IR) experiments demonstrated that the epoxide conversion rate of nanocomposites was slightly increased compared to neat resin. The beneficial role of the BA can be explained by the participation of hydroxyl groups at the particle surface in photopolymerization processes and by the complementary contribution of p-toluenesulfonic acid surface modifier and water molecules introduced into the system with nanoparticles.
Dose enhancement by gold nanoparticles (AuNP) was shown to increase the biological effectiveness of radiation damage in biomolecules and tissue. Most of the current studies focus on external beam therapy on combination with AuNP. Here we present a Monte-Carlo study (Geant4) to characterise radioactive AuNP. Radioactive ¹⁹⁸Au emits beta and gamma rays and is considered for applications with solid tumours. To effectively apply ¹⁹⁸AuNP their energy deposit characteristics have to be determined in terms of intrinsic and extrinsic properties e.g. AuNP diameter, AuNP density, and their clustering behaviour. After each decay process, the energy deposit, inelastic scattering events, kinetic energy spectrum of secondary particles within the AuNP themselves and in a spherical target volume of water up to 1 μm radius were determined. Simulations were performed for AuNP radii ranging from 2.5 nm to 20 nm radius, different cluster sizes and densities. The results show an increase of the energy deposit in the vicinity of the AuNP up to 150 nm. This effect nearly vanishes for distances up to one micron. For the case of AuNP clusters and the same activity, the enhancement of the energy deposit increases with the relative gold mass percentage and therefore can be adjusted by changing AuNP radius or clustering behaviour.
Superglassy polymers with a large fractional free volume have emerged as novel materials with a broad range of applications, especially in the field of membrane separations. Highly permeable addition-type substituted polynorbornenes with high thermal resistance and chemical stability are among the most promising materials. The major obstacle for extending the practical membrane application is their strong tendency to physical aging, leading to a partial decline in their superior transport performance over time. In the present study, broadband dielectric spectroscopy with complementary X-ray scattering techniques were employed to reveal changes in microporous structure, molecular mobility, and conductivity by systematic
comparison of two polynorbornenes with different numbers of trimethylsilyl side groups. Their response upon heating (aging) was compared in terms of structure, dynamics, and charge transport behavior. Furthermore, a detailed analysis of the observed
Maxwell−Wagner−Sillars polarization at internal interfaces provides unique information about the microporous structure in the
solid films. The knowledge obtained from the experiments will guide and unlock potential in synthesizing addition-type polynorbornenes with versatile properties.
Copper has a strong bactericidal effect against multi-drug resistant pathogens and polyethers are known for their resistance to biofilm formation. Herein, we combined Cu nanoparticles (NPs) and a polyether Plasma polymer in the form of nanocomposite thin films and studied whether both effects can be coupled. Cu NPs were produced by magnetron sputtering via the aggregation in a cool buffer gas whereasolyether layers were synthesized by Plasma-Assisted Vapor Phase Deposition with poly(ethylene oxide) (PEO) used as a precursor. In situ specific heat spectroscopy and XPS analysis revealed the formation of a modified polymer layer around the NPs which propagates on the scale of a few nanometers from the Cu NP/polymer interface and then transforms into a bulk polymer phase. The chemical composition of the modified layer is found to be ether-deficient due to the catalytic influence of copper whereas the bulk polymer Phase exhibits the chemical composition close to the original PEO. Two cooperative glass transition phenomena are revealed that belong to the modified polymer layer and the bulk phase. The former is characterized by constrained mobility of polymer segments which manifests itself via a 30 K increase of dynamic glass transition temperature. Furthermore, the modified layer is characterized by the heterogeneous structure which results in higher fragility of this layer as compared to the bulk phase. The Cu NPs/polyether thin films exhibit reduced Protein adsorption; however, the constrained segmental dynamics leads to the Deterioration of the non-fouling properties for ultra-thin polyether coatings. The films are found to have a bactericidal effect against multi-drug resistant Gram-positive Methicillin-Resistant Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa.
We show that complex physical and chemical interactions between boehmite nanoparticles and epoxy drastically affect matrix properties, which in the future will provide tuning of material properties for further optimization in applications from automotive to aerospace. We utilize intermodulation atomic force microscopy (ImAFM) for probing local stiffness of both particles and polymer matrix. Stiff particles are expected to increase total stiffness of nanocomposites and the stiffness of polymer should remain unchanged. However, ImAFM revealed that stiffness of matrix in epoxy/boehmite nanocomposite is significantly higher than unfilled epoxy. The stiffening effect of the boehmite on epoxy also depends on the particle concentration. To understand the mechanism behind property alteration induced by boehmite nanoparticles, network architecture is investigated using dynamic mechanical thermal analysis (DMTA). It was revealed that although with 15 wt% boehmite nanoparticles the modulus at glassy state increases, crosslinking density of epoxy for this composition is drastically low.
Understanding the interaction between nanoparticles and the matrix and the properties of interphase is crucial to predict the macroscopic properties of a nanocomposite system. Here, we investigate the interaction between boehmite nanoparticles (BNPs) and epoxy using different atomic force microscopy (AFM) approaches. We demonstrate benefits of using multifrequency intermodulation AFM (ImAFM) to obtain information about conservative, dissipative and van der Waals tip-surface forces and probing local properties of nanoparticles, matrix and the interphase.
We utilize scanning kelvin probe microscopy (SKPM) to probe surface potential as a tool to visualize material contrast with a physical parameter, which is independent from the mechanics of the surface. Combining the information from ImAFM stiffness and SKPM surface potential results in a precise characterization of interfacial region, demonstrating that the interphase is softer than epoxy and boehmite nanoparticles. Further, we investigated the effect of boehmite nanoparticles on the bulk properties of epoxy matrix. ImAFM stiffness maps revealed the significant stiffening effect of boehmite nanoparticles on anhydride-cured epoxy matrix. The energy Dissipation of epoxy Matrix locally measured by ImAFM shows a considerable increase compared to that of neat epoxy. These measurements suggest a substantial alteration of epoxy structure induced by the presence of boehmite.
The phase behavior and molecular ordering of hexakishexyloxy triphenylene (HAT6) DLC under cylindrical nanoconfinement is studied utilizing differential scanning calorimetry (DSC) and dielectric spectroscopy (DS), where cylindrical nanoconfinement is established through embedding HAT6 into the nanopores of anodic aluminum oxide membranes (AAO), and a silica membrane with pore diameters ranging from 161 nm down to 12 nm. Both unmodified and modified pore walls were considered, and in the latter case the pore walls of AAO membranes were chemical treated with n octadecylphosphonic acid (ODPA) resulting in the formation of a 2.2 nm thick layer of grafted alkyl chains. Phase transition enthalpies decrease with decreasing pore size, indicating that a large proportion of the HAT6 molecules within the pores has a disordered structure, which increases with decreasing pore size for both pore walls. In the case of the ODPA modification the amount of ordered HAT6 is increased compared to the unmodified case. The pore size dependencies of the phase transition temperatures were approximated using the Gibbs Thomson equation, where the estimated surface tension is dependent on the molecular ordering of HAT6 molecules within the pores and upon their surface. DS was employed to investigate the molecular ordering of HAT6 within the nanopores. These investigations revealed that with a pore size of around 38 nm, for the samples with the unmodified pore walls, the molecular ordering changes from planar axial to homeotropic radial. However, the planar axial configuration, which is suitable for electronic applications, can be successfully preserved through ODPA modification for most of the pore sizes.
We investigate the nearfield dipole mobility of protein membranes in a wide frequency range from 3 kHz to 10 GHz. The results of our nanoscale dielectric images and spectra of bacteriorhodopsin (bR) reveal Debye relaxations with time constants of τ ∼ 2 ns and τ ∼ 100 ns being characteristic of the Dipole moments of the bR retinal and α-helices, respectively. However, the dipole mobility and therefore the protein biophysical function depend critically on the amount of surface water surrounding the protein, and the characteristic mobility in the secondary structure is only observed for humidity levels <30%. Our results have been achieved by adding the frequency as a second fundamental dimension to quantitative dielectric microscopy. The key elements for the success of this advanced technique are the employed heterodyne detection scheme, the broadband electrical signal source, a high frequency optimized cabling, development of calibration procedures and precise finite element modelling. Our study demonstrates the exciting possibilities of broadband dielectric microscopy for the investigation of dynamic processes in cell bioelectricity at the individual molecular level. Furthermore, the technique may shed light on local dynamic processes in related materials science applications like semiconductor Research or nano-electronics.
The molecular mobility of the highly asymmetric miscible blend poly(vinyl methyl ether)/polystyrene was investigated by broadband dielectric (frequency range 10^-1 Hz – 10^9 Hz) and specific heat spectroscopy (frequency range 10^1 Hz – 10^4 Hz). The dielectric spectra revealed a complex molecular dynamic behavior, where three different relaxation processes were observed. At temperatures below the glass transition temperature an α´-relaxation was found, with an Arrhenius-like temperature dependence of its relaxation rates. It is assigned to localized fluctuations of the confined PVME segments within a frozen glassy matrix dominated by PS. Above the thermal glass transition temperature two processes with a VFT behavior of their relaxation rates were detected called α1- and α2-relaxation, both originating from PVME dipoles fluctuating in PS-rich environments, however with diverse PS concentrations. The relevant length scales for the processes are assumed to be different, corresponding to the Kuhn segment length for the former relaxation and to the CRR for the latter one. The observed multiple glassy dynamics result from spatial local compositional heterogeneities on a microscopic level. Additionally, SHS investigations were performed for the first time for this system, proving an existence of a fourth relaxation process (α3-relaxation) due to the cooperative fluctuations of both PS and PVME segments. The separation between the thermal α3- and dielectric α2-relaxation increases dramatically with increasing polystyrene concentration, proving that the thermal response is dominated by PS.
Reliable simulation of polymers on an atomistic length scale requires a realistic representation of the cured material. A molecular modelling method for the curing of epoxy systems is presented, which is developed with respect to efficiency while maintaining a well equilibrated system. The main criterion for bond formation is the distance between reactive groups and no specific reaction probability is prescribed. The molecular modelling is studied for three different mixing ratios with respect to the curing evolution of reactive Groups and the final curing stage. For the first time, the evolution of reactive groups during the curing process predicted by the molecular modelling is validated with near-infrared spectroscopy data, showing a good agreement between simulation results and experimental measurements. With the proposed method, deeper insights into the curing mechanism of epoxy systems can be gained and it allows us to provide reliable input data for molecular Dynamics simulations of material properties.
In this study, a method for the determination of tire and road wear particle (TRWP) contents in particulate samples from road Environment was developed. Zn was identified as the most suitable elemental marker for TRWP, due to its high concentration in tire tread and the possibility of separation from other Zn sources. The mean concentration of 21 tire samples was 8.7 ± 2.0 mg Zn/g. Before quantification in samples from road environment, TRWP were separated from the particulate matrix by density separation. Method development was conducted using shredded tread particles (TP) as a surrogate for TRWP.
Recovery of TP from spiked sediment was 95 ± 17% in a concentration range of 2 - 200 mg TP/g. TP determination was not affected by other Zn containing solids or spiked Zn-salts. By adjusting the density of the separation solution to 1.9 g/cm3, more than 90% of total TRWP were separated from the sample matrix. TRWP concentrations in particulate matter collected in two road runoff treatment Systems ranged from 0.38 to 150 mg TRWP/g. Differences in quantified TRWP contents of the two Systems indicate changes in particle dynamics due to ageing and aggregation processes. The developed method allows TRWP determination in road runoff and in environments that are influenced by road traffic. The validated separation procedure can also be applied for TRWP characterization in future studies.