6 Materialchemie
Filtern
Dokumenttyp
- Zeitschriftenartikel (129)
- Beitrag zu einem Tagungsband (2)
- Buchkapitel (1)
Sprache
- Englisch (132)
Referierte Publikation
- ja (132) (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)
- 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)
- 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)
- 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 (132) (entfernen)
Paper des Monats
- ja (6)
The occurrence of small particles consisting of organic polymers, so-called microplastic (MP), in aquatic Environments attracts increasing interest in both public and science. Recent sampling campaigns in surface Waters revealed substantial numbers of particles in the size range from a few micrometers to a few millimeters. In order to validate sample preparation, identification and quantification and to investigate the behavior of MP particles and potential toxic effects on organisms, defined MP model particles are needed. Many studies use spherical compounds that probably behave differently compared to irregularly shaped MP found in environmental samples.
However, preparation and handling of MP particles are challenging tasks and have been systematically investigated in the present study. Polystyrene (PS) as a commonly found polymer with a density slightly above that of water was selected as polymer type for milling and fractionation studies. A cryogenic ball mill proved to be practical and effective to produce particles in the size range from 1 to 200 μm. The yield of small particles increased with increasing pre-cooling and milling durations. Depending on the concentration and the size, PS particles do not completely disperse in water and particles partly creep vertically up along glass walls. Stabilized MP suspensions without use of surfactants that might harm organisms are needed for toxicological studies. The stabilization of PS particle suspensions with ozone treatment reduced the wall effect and increased the number of dispersed PS particles but increased the dissolved organic carbon concentration and changed the size Distribution of the particles.
Analysis of microplastic particles (MP) in environmental samples needs sophisticated techniques and is time intensive due to sample preparation and detection. An alternative to the most common (micro ) spectroscopic techniques, FTIR or Raman spectroscopy, are the thermoanalytical methods, where specific decomposition products can be analyzed as marker compounds for different kind of plastics types and mass contents. Thermal extraction desorption gas chromatography mass spectrometry (TED-GC-MS) allows the fast identification and quantification of MP in environmental samples without sample preparation. Whereas up to now only the analysis of thermoplastic polymers was realized, this is the first time that even the analysis of tire wear (TW) content in environmental samples is possible. Various marker compounds for TW were identified. They include characteristic decomposition products of elastomers, antioxidants and vulcanization agents. Advantages and drawbacks of these marker substances were evaluated. Environmental samples from street run off were exemplarily investigated and presented.
The effects of weathering exposure on unfilled and filled thermoplastic polyurethanes (TPU) materials are described as performed under different humidity conditions. For this purpose, a weathering device was used with UV-A 340 nm lamps at a constant temperature of 40 °C. The effects of environmental (UV and humidity condition) degradation on the frictional properties of TPU materials are presented along with surface analyses to characterize the chemistry of the degradative process. Photooxidative degradation of unfilled polymer leads to deterioration of physical and mechanical properties, which affects its tribological behavior significantly. Due to crosslinking, the stiffness of the material increases, reducing drastically the friction coefficient of unfilled TPUs. The frictional behavior of glass fiber reinforced TPU is less affected by radiation.
Branched Polyurethanes Based on Synthetic Polyhydroxybutyrate with Tunable Structure and Properties
(2018)
Branched, aliphatic polyurethanes (PURs) were synthesized and compared to linear analogues. The influence of polycaprolactonetriol and synthetic poly([R,S]-3-hydroxybutyrate) (R,S-PHB) in soft segments on structure, thermal and sorptive properties of PURs was determined.
Using FTIR and Raman spectroscopies it was found that increasing the R,S-PHB amount in the structure of branched PURs reduced a tendency of urethane groups to hydrogen bonding. Melting enthalpies (on DSC thermograms) of both soft and hard segments of linear PURs were higher than branched PURs, suggesting that linear PURs were more crystalline. Oil sorption by samples of linear and branched PURs, containing only polycaprolactone chains in soft segments, was higher than in the case of samples with R,S-PHB in their structure. Branched PUR without R,S-PHB absorbed the highest amount of oil. Introducing R,S-PHB into the PUR structure increased water sorption.
Thus, by operating the number of branching and the amount of poly([R,S]-3-hydroxybutyrate) in soft segments thermal and sorptive properties of aliphatic PURs could be controlled.
A combination of different complementary methods is employed to investigate scaling of the molecular dynamics of two different liquid crystals. Each method is sensitive to different kind of fluctuations and provides therefore a different window to look at the molecular dynamics. In detail, broadband dielectric spectroscopy is combined with specific heat spectroscopy and neutron scattering. As systems the nematic liquid crystal E7 and a discotic liquid crystalline pyrene are considered. First of all it was proven that both systems show all peculiarities which are characteristic for glassy dynamics and the glassy state. Especially for the nematic liquid crystal E7 it could be unambiguously shown by a combination of dielectric and specific heat spectroscopy that the tumbling mode is the underlying motional process responsible for glassy dynamics. Dielectric investigations on the discotic liquid crystalline pyrene reveal that at the phase transition from the plastic crystalline to the hexagonal columnar liquid crystalline phase the molecular dynamics changes from a more strong to fragile temperature dependence of the relaxation rates. Moreover a combination of results obtained by specific heat spectroscopy with structural methods allows an estimation of the length scale relevant for the glass transition.
Solution doping of off-the-shelf plastic optical fibers (POFs) represents rather simple and cheap way for preparing custom cladding-doped POFs (CD-POFs) with short to medium lengths. CD-POFs are especially attractive for environmental sensing applications, but might be of interest for illumination task as well. In this work, the proposed doping technique is tested with three different commercial low-cost polymethyl methacrylate (PMMA) POFs; Eska CK-40 and Eska GK-40 from Mitsubishi Rayon and Raytela PGU-FB1000 from Toray. The aim of the work is to aid the selection of the most suitable fiber yielding highest optical quality of prepared CD-POFs. Firstly, the optimal doping times are determined for the individual fiber types using short fiber samples. Secondly, longer 10 m CD-POFs are prepared from all tested fibersusing the optimized doping procedure. Finally, attenuation of pristine POFs and prepared CD-POFs is measured using optical time domain reflectometry in order to characterize the impacts of the doping on fiber optical properties. In addition, the importance of post-doping drying procedure for CD-POF optical performance is investigated as well. The results suggest that, although doping of all tested fibers is generally feasible, Eska CK-40 is the most suitable candidate with regard to the Doping efficiency and fiber post-doping performance.
Polymers with intrinsic microporosity (PIMs) represent a novel, innovative class of materials with great potential in various applications from high-performance gas separation membranes to electronic devices. Here for the first time, for PIM-1, as the archetypal PIM, fast scanning calorimetry provides definitive evidence for a glass transition (Tg=715 K, heating rate 3·10^4 K/s) by decoupling the time-scales responsible for glass transition and decomposition. As the rigid molecular structure of PIM-1 prevents any conformational changes, small-scale bend and flex fluctuations must be considered the origin of its glass transition. This result has strong implications for the fundamental understanding of the glass transition and for the physical aging of PIMs and other complex polymers, both topical problems of materials science.
Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms.
Dynamics and ionic conductivity of ionic liquid crystals forming a hexagonal columnar mesophase
(2018)
For the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflate ionic liquid crystals (ILCs) having different length of alkyl chains were investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). By self-assembly, these ILCs can form a hexagonal ordered mesophase besides plastic crystalline phases and the isotropic state. Three dielectric active processes were found by BDS for both samples. At low temperatures, a γ-process in the plastic crystalline state is observed which is assigned to localized fluctuations of methyl groups including nitrogen atoms in the guanidinium head. At higher temperatures but still in the plastic crystalline state, an α1-process takes place. An α2 process was detected by SHS but with a completely different temperature dependence of the relaxation times than that of the α1-relaxation. This result is discussed in detail, and different molecular assignments of the processes are suggested. At even higher temperatures, electrical conductivity is detected and an increase in the DC conductivity by four orders of magnitude at the phase transition from the plastic crystalline to the hexagonal columnar mesophase is found. This result is traced to a change in the charge transport mechanism from a delocalized electron hopping in the stacked aromatic systems (in the plastic phase) to one dominated by an ionic conduction in the quasi-1D ion channels formed along the supermolecular columns in the ILCs hexagonal mesophases.
Solution doping of commercial polymethyl methacrylate (PMMA) polymer optical fibers (POFs) is presented as a novel approach for preparation of custom cladding-doped POFs (CD-POFs). The presented method is based on a solution-mediated diffusion of dopant molecules into the fiber cladding upon soaking of POFs in a methanol-dopant solution. The method was tested on three different commercial POFs using Rhodamine B as a fluorescent dopant. The dynamics of the diffusion process was studied in order to optimize the doping procedure in terms of selection of the most suitable POF, doping time and conditions. Using the optimized procedure, longer segment of fluorescent CD-POF was prepared and its performance was characterized. Fiber’s potential for sensing and illumination applications was demonstrated and discussed. The proposed method represents a simple and cheap way for fabrication of custom, short to medium length CD-POFs with various dopants.