Novel perfluoropolyethers containing 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole blocks: synthesis and characterization

Peroxidic perfluoropolyethers (PFPEs) are industrial intermediates used by Solvay Solexis for the preparation of different classes of (per)fluoropolyethers (Fomblin^®, Galden^®, Solvera^®, Fluorolink^®). The chemistry of these peroxidic compounds has been recently exploited for the synthesis of novel PFPE block copolymers. In the present work we report the synthesis, the structural and physical-chemical characterization of block copolymers obtained by the reaction of peroxidic PFPEs with 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, a cyclic homopolymerizable perfluoroolefin. These block copolymers combine the most attractive properties of the PFPEs, like the excellent lubrication, the high thermal stability and the optical transparency, with new specific properties which are related to the perfluorodioxolenic blocks.     

Automated determination of diazepam in spiked alcoholic beverages associated with drug-facilitated crimes

In this work, a multipumping flow system (MPFS) coupled to a photodegradation unit was developed, for the first time, for the determination of diazepam (a benzodiazepine) in spiked alcoholic beverages by fluorimetry. The main features of MPFS such as, high portability, versatility and straightforward automation and control combined with the efficiency and simplicity of photodegradation and the selectivity and sensitivity of fluorimetric detection makes the developed analytical methodology an attractive tool and a valuable contribution for the prevention of drug-facilitated crimes (DFC). Drug-facilitated crimes involve the unauthorized administration of strong central nervous system depressant drugs, which have the capability of preventing victims from resist to the action of the perpetrator or fighting off. Most often, the drugs identified as being used in DFC are surreptitiously placed in drinks served to potential victims in entertainment places, like night clubs.Five commercial alcoholic beverages (Eristoff^®, Smirnoff^®, Bacardi^®, Dry Gin^® and Brazilian Cachaça 51^®) spiked with diazepam were analyzed by the proposed methodology, and the results revealed good agreement with those obtained through a HPLC comparison procedure. Relative deviations comprised between −1.97 and 2.05% were achieved, and additionally, the application of a paired t-test, revealed the absence of any statistical difference for a confidence level of 95% (n = 5). The detection limit was approximately 2.02 mg L⁻¹.     

Dimensionally stable Nafion–polyethylene composite membranes for direct methanol fuel cell applications

Nafion^® impregnated Solupor^®, microporous UHMWPE film, (N-PE), Nafion^®117 (N117) and a membrane prepared using a DE2020 Nafion^® dispersion (DE2020) were characterized with respect to their swelling degree (SD), methanol cross-over, proton conductivity and DMFC performance at various methanol concentrations in order to understand the effect of impregnation of an ion-conductive polymer membrane to the fuel cell performance.     

Practical synthesis of the calcimimetic agent, cinacalcet

A practical synthesis of cinacalcet (Sensipar^®, Mimpara^®) is described. The synthesis starts from readily available starting materials and relies on safe and practical reaction conditions. The sequence comprises three synthetic steps and only one isolation point. The overall yield for the sequence is 85%.     

NOR and nitroxide-based HAS in accelerated photooxidation of carbon-chain polymers; Comparison with secondary HAS: An ESRI and ATR FTIR study

Understanding processes resulting in heterogeneous degradation in polymers is of extreme importance for improving their stabilization and minimizing negative impact of photooxidation on the material properties. We adopted modern physical techniques for studies of spatial distribution of intermediates and products of photodegradation during accelerated ageing of four commodity polymers, polypropylene (PP), polyethylene (PE), polystyrene (PS) and poly(ethylene-co-norbornene) (Topas^®, TP) stabilized with hindered amine stabilizer (HAS). Concentration profiles of nitroxides inside polymer plaques along the direction perpendicular to their surface were determined by electron spin resonance imaging (ESRI) as a function of the duration of the accelerated photooxidation. We present data characterizing stabilization activity of three alkoxyamine derivatives of HAS (Tinuvin^® NOR 123, Tinuvin^® NOR 371, Flamestab^® NOR 116), Chimasorb^® 119 structurally similar to Flamestab^® NOR 116, and nitroxide-based HAS Dastib^® 1045 and compare them with the data characterizing stabilization activity of the secondary HAS (>NH) Tinuvin^® 770. ESRI data are complemented by ATR FTIR spectroscopic detection of oxidation products on the surface and inside the plaques and by data characterizing diffusive optical transmittance of the polymer plaques in the spectral region 280-400 nm (terrestrial range of the solar UV radiation).     

Uranium aqueous speciation in the vicinity of the former uranium mining sites using the diffusive gradients in thin films and ultrafiltration techniques

The performance of the Diffusive Gradients in Thin films (DGT) technique with Chelex^®-100, Metsorb™ and Diphonix^® as binding phases was evaluated in the vicinity of the former uranium mining sites of Chardon and L'Ecarpière (Loire-Atlantique department in western France). This is the first time that the DGT technique with three different binding agents was employed for the aqueous U determination in the context of uranium mining environments. The fractionation and speciation of uranium were investigated using a multi-methodological approach using filtration (0.45 μm, 0.2 μm), ultrafiltration (500 kDa, 100 kDa and 10 kDa) coupled to geochemical speciation modelling (PhreeQC) and the DGT technique. The ultrafiltration data showed that at each sampling point uranium was present mostly in the 10 kDa truly dissolved fraction and the geochemical modelling speciation calculations indicated that U speciation was markedly predominated by CaUO₂(CO₃)₃²⁻. In natural waters, no significant difference was observed in terms of U uptake between Chelex^®-100 and Metsorb™, while similar or inferior U uptake was observed on Diphonix^® resin. In turn, at mining influenced sampling spots, the U accumulation on DGT-Diphonix^® was higher than on DGT-Chelex^®-100 and DGT-Metsorb™, probably because their performance was disturbed by the extreme composition of the mining waters. The use of Diphonix^® resin leads to a significant advance in the application and development of the DGT technique for determination of U in mining influenced environments. This investigation demonstrated that such multi-technique approach provides a better picture of U speciation and enables to assess more accurately the potentially bioavailable U pool.     

Transport properties of a co-poly(amide-12-b-ethylene oxide) membrane: A comparative study between experimental and molecular modelling results

An experimental and theoretical study has been used to investigate gas diffusion and solubility in PEBAX^®2533 block copolymer membrane. Molecular simulations using COMPASS force field have been successful in predicting the gas-transport properties of a PEBAX^®2533 block copolymer and of a pure PTMO homopolymer. Gusev–Suter transition state theory (TST) and Monte Carlo methods are used for simulating the transport of five permanent gases (He, H₂, N₂, O₂, CO₂ and CH₄). Theoretical and experimental data have been compared.     

Aspects of the thermal and photostabilisation of high styrene-butadiene copolymer (SBC)

The thermal and photo-oxidative stabilisation of high styrene-butadiene copolymer (SBC) with high styrene content (K-Resin) has been studied using a variety of analytical and spectroscopic methods including yellowness, luminescence and FT-IR spectroscopy coupled with hydroperoxide analysis in order to understand the nature and effectiveness of the processes involved. The next stage of the program was to evaluate the effects of various chemical/solvent treatments on the role of metal ions/residual catalysts and hydroperoxides in the thermal and photostabilisation of SBS as well as combinations of phenolic antioxidants and phosphites/phosphonites. Other additives, such as HALS and a metal deactivator, were also added to the combinations of phenolic and phosphite antioxidants in order to study their behaviour and efficiency. The chemical treatments appeared to stabilise SBS against thermal oxidation to a greater or lesser extent. Phosphoric acid treatment via reflux and zinc dithiocarbamate treatments showed better performances than the rest of the treatments, the latter was particularly effective at inhibiting the discolouration. During photo-oxidation, on the other hand, chemical treatments involving phosphoric acid and pre-thermal effects showed the importance of catalyst effects. The addition of phenolic antioxidants, phosphites/phosphonites, metal deactivator and HALS was found to stabilise the SBS against thermal and photo-oxidation. In thermal oxidation, the combination of Irganox^® 1010/Irgafos^® 168 was found to effectively stabilise the polymer when the finalisation of the polymerisation was with adipic acid. When the same antioxidants were used, but with polymer finalised with BHT, strong yellowing was observed and a higher amount of hydroperoxides and oxidation products. Increasing the amount of antioxidants did not increase the stabilisation efficiency. The stabilisation efficiency of Irganox^® 1010 combined with Alkanox^® P-24 was found to be more effective than when it was combined with Irgafos^® 168. The formulations containing Irgafos^® 168/Irganox^® 1010 and Irgafos^® 168/Irganos^® 1330 were more effective in colour protection and retarding the formation of oxidation products than the combinations of Irgafos^® 168/Irganox^® 3114 and Irgafos^® 168/Lowinox^® 1790. The effect of the addition of HALS, such as Tinuvin^® 770, Tinuvin^® 622 and Chimassorb^® 944, and a metal deactivator, such as Irganox^® MD 1024, to the combination of Irgafos^® 168/Irganox^® 1010 was found to be antagonistic. In photo-oxidation, a combination of Irganox^® 1010/Irgafos^® 168 protected the polymer efficiently, when the polymerisation of the polymer was finalised with adipic acid. When the polymerisation was finalised with BHT, a higher amount of hydroperoxides and oxidation products was found. An increase in the amount of antioxidants did not enhance the stability of the polymer. The addition of Alkanox^® P-24 exhibited an opposite effect to that seen in thermal oxidation, as the stabilisation efficiency was less effective than with Irgafos^® 168. The formulation containing Irgafos^® 168/Irganox^® 1010 was found to be the most efficient compared with the other phenolic antioxidants. The addition of Tinuvin^® 770 to the formulation Irgafos^® 168/Irganox^® 1010 was found to have a synergistic effect. The addition of polymeric HALS or Irganox^® MD 1024, a metal deactivator, had an antagonistic effect on the stabilisation of the polymer. Disruption of the excimer sites in the styrenic phase also correlated with stabilisation effects.     

Microwave assisted synthesis of the fragrant compound Calone 1951

Calone 1951^®, 7-methyl-benzo[b][1,4]dioxepin-3-one, possesses a strong marine, ozone note with floral nuances and is synthesised via a three-step procedure using microwave irradiation. High yields were obtained, and reaction times reduced to a few minutes, allowing for an efficient and inexpensive synthesis of Calone 1951^®.     

The effect of spatial confinement of Nafion in porous membranes on macroscopic properties of the membrane

Polyelectrolytes were incorporated into porous reinforcing materials to study the properties of ionomers in confined spaces and to determine the effect of the porous material on the behaviour of the membranes. Nafion^® was imbibed into porous polypropylene (Celgard^®), ultra-high-molecular weight polyethylene (Daramic^®), and polytetrafluoroethylene (PTFE) films. Through the use of reinforcing materials, it is possible to prepare membranes that are thinner, but stronger than pure ionomer membranes. Thin reinforced membranes have advantages such as lower areal resistance (as low as 0.14 Ω cm² for 57 μm CG3501 + Nafion^® compared to 0.34 Ω cm² for 89 μm cast Nafion^®) and lower dimensional changes due to swelling (as low as a 4% change in length and width for WDM + Nafion^® compared to 13% for cast Nafion^®). Using reinforcing materials results in a reduction in important membrane properties compared to bulk Nafion^®, such as proton conductivity (as low as 0.016 S cm⁻¹ for CG3401 + Nafion^® compared to 0.076 S cm⁻¹ for cast Nafion^®), effective proton mobility (as low as 3.2 × 10⁻⁴ cm² V⁻¹ s⁻¹ CG3401 + Nafion^® compared to 7.6 × 10⁻⁴ cm² V⁻¹ s⁻¹ for cast Nafion^®), and water vapour permeance (as low as 0.036 g h⁻¹ Pa⁻¹ m⁻² for WDM + Nafion^® compared to 0.056 g h⁻¹ Pa⁻¹ m⁻² for cast Nafion^®). By normalizing the membrane properties with respect to ionomer content, it was possible to examine the properties of the Nafion^® inside the pores of the membranes. The proton conductivity (as low as 0.032 S cm⁻¹ for CG3401 + Nafion^®), effective proton mobility (as low as 3.6 × 10⁻⁴ cm² V⁻¹ s⁻¹ for CG3401 + Nafion^®), and water vapour permeability (as low as 2.7 × 10⁻⁶ g h⁻¹ Pa⁻¹ m⁻¹ for PTFE MP 0.1 + Nafion^®) of the ionomer in the membrane are also diminished compared to bulk Nafion^® due to decreased connectivity of the ionomer and a restriction in macromolecular motions caused by the pore walls. A series of porous materials with increasing pore were also examined. As the pore size of the PTFE MP materials increased from 0.1 μm to 10 μm, the proton conductivity (0.022 S cm⁻¹ to 0.041 S cm⁻¹), effective proton mobility ((4.1 to 5.6) × 10⁻⁴ cm² V⁻¹ s⁻¹), and water vapour permeability ((2.4 to 4.3) × 10⁻⁶ g h⁻¹ Pa⁻¹ m⁻¹) of the reinforced membranes improved with increasing pore size and the properties of the ionomer inside the membranes approached the value of bulk Nafion^®.     

Characterization of new types of stationary phases for fast and ultra-fast liquid chromatography by signal processing based on AutoCovariance Function: A case study of application to Passiflora incarnata L. extract separations

In this study, a comparative investigation was performed of HPLC Ascentis^® (2.7 μm particles) columns based on fused-core particle technology and Acquity^® (1.7 μm particles) columns requiring UPLC instruments, in comparison with Chromolith™ RP-18e columns. The study was carried out on mother and vegetal tinctures of Passiflora incarnata L. on one single or two coupled columns. The fundamental attributions of the chromatographic profiles are evaluated using a chemometric procedure, based on the AutoCovariance Function (ACVF). Different chromatographic systems are compared in terms of their separation parameters, i.e., number of total chemical components (m_tot), separation efficiency (σ), peak capacity (n_c), overlap degree of peaks and peak purity. The obtained results show the improvements achieved by HPLC columns with narrow size particles in terms of total analysis time and chromatographic efficiency: comparable performance are achieved by Ascentis^® (2.7 μm particle) column and Acquity^® (1.7 μm particle) column requiring UPLC instruments. The ACVF plot is proposed as a simplified tool describing the chromatographic fingerprint to be used for evaluating and comparing chemical composition of plant extracts by using the parameters D% – relative abundance of the deterministic component – and c_EACF – similarity index computed on ACVF.     

Evaluation of diffusive gradients in thin-films using a Diphonix resin for monitoring dissolved uranium in natural waters

Commercially available Diphonix^® resin (TrisKem International) was evaluated as a receiving phase for use with the diffusive gradients in thin-films (DGT) passive sampler for measuring uranium. This resin has a high partition coefficient for actinides and is used in the nuclear industry. Other resins used as receiving phases with DGT for measuring uranium have been prone to saturation and significant chemical interferences. The performance of the device was evaluated in the laboratory and in field trials. In laboratory experiments uptake of uranium (all 100% efficiency) by the resin was unaffected by varying pH (4–9), ionic strength (0.01–1.00 M, as NaNO₃) and varying aqueous concentrations of Ca²⁺ (100–500 mg L⁻¹) and HCO₃⁻ (100–500 mg L⁻¹). Due to the high partition coefficient of Diphonex^®, several elution techniques for uranium were evaluated. The optimal eluent mixture was 1 M NaOH/1 M H₂O₂, eluting 90% of the uranium from the resin. Uptake of uranium was linear (R² = 0.99) over time (5 days) in laboratory experiments using artificial freshwater showing no saturation effects of the resin. In field deployments (River Lambourn, UK) the devices quantitatively accumulated uranium for up to 7 days. In both studies uptake of uranium matched that theoretically predicted for the DGT. Similar experiments in seawater did not follow the DGT theoretical uptake and the Diphonix^® appeared to be capacity limited and also affected by matrix interferences. Isotopes of uranium (U²³⁵/U²³⁸) were measured in both environments with a precision and accuracy of 1.6–2.2% and 1.2–1.4%, respectively. This initial study shows the potential of using Diphonix^®-DGT for monitoring of uranium in the aquatic environment.     

PEG modified poly(amide-b-ethylene oxide) membranes for CO2 separation

In the present work, membranes from commercially available Pebax^® MH 1657 and its blends with low molecular weight poly(ethylene glycol) PEG were prepared by using a simple binary solvent (ethanol/water). Dense film membranes show excellent compatibility with PEG system up to 50 wt.% of content. Gas transport properties have been determined for four gases (H₂, N₂, CH₄, CO₂) and the obtained permeabilities were correlated with polymer properties and morphology of the membranes. The permeability of CO₂ in Pebax^®/PEG membrane (50 wt.% of PEG) was increased two fold regarding to the pristine Pebax^®. Although CO₂/N₂ and CO₂/CH₄ selectivity remained constant, an enhancement of CO₂/H₂ selectivity (∼11) was observed. These results were attributed to the presence of EO units which increases CO₂ permeability, and to a probable increase of fractional free-volume. Furthermore, for free-volume discussion and permeability of gases, additive and Maxwell models were used.     

The Pharmaceutical Use of Captisol®: Some Surprising Observations

The purpose of this paper is to share some recent observations on the pharmaceuticaluses and properties of Captisol^® or SBE_7M--CD in controlled porosity osmotic pump tablets (CP-OPT) and the underlying mechanism/sthat lead to apparent zero-order drug release pattern. It would have been simple toattribute the apparent zero-order release mechanism/s of poorly water-soluble drugsfrom CP-OPTs and pellets utilizing Captisol^®as both a solubilizing andosmotic agent, to purely osmotic and diffusional components. However, the mechanismmay be more related to a counterbalancing of physical properties as the concentration of Captisol^®changes within the matrix. Specifically, the initial concentration of Captisol^®within a core is 0.3–0.4M. When this drops to lower values an osmotic pressure drop occurs across the membrane. Therefore, drug release should not follow apparent zero-order kinetics if all the drug is solubilized. However, as the viscosity within the tablet also drops, the apparent diffusion coefficient of both Captisol^® and drug increases. Therefore, it appears that there is an initial resistance (hydraulic pressure) to fluid flow from the tablet through the rate-limiting microporous membrane. This resistance decreases so that even as osmotic pressure and concentration differences drop with time, counterbalancing faster release occurs. Osmotic driving force appears to be the most important initial driving force but a diffusional component becomes more significant with time.     

Effect of thermal history on the mechanical properties of three polypropylene impact-copolymers

The effect of thermal history on static mechanical properties and impact fracture behavior of three reactor polypropylene impact-copolymers (ICPPs) was investigated for three ICPPs prepared using commercial Innovene^®, Unipol^® and Spheripol^® polymerization technologies. Multiple extrusion employing a co-rotating twin-screw extruder resulted in a significant reduction of the molecular weight of the PP homopolymer phase evidenced by the increasing melt flow index (MFI). Neither cross-linking of the ethylene-propylene rubber (EPR) phase nor EPR particle coarsening was detected for any of the ICPPs after 5 consecutive extrusions. Decreasing molecular weight of the PP homopolymer phase caused change in the crystalline morphology of injection molded specimens due to the change in crystallization kinetics and reduction of the number of tie molecules, however, the overall degree of crystallinity did not change, significantly. The static tensile mechanical properties (E, σ_y, ?_b), critical strain energy release rate, G_c, and the Charpy notched impact strength, a_k, decreased with increasing MFI in a monotonous manner for all the ICPPs investigated. Despite significant differences between the absolute values of the mechanical properties for the three ICPPs, the MFI dependence of the σ_y and G_c relative to that for the unaffected ICPP fell on a single master curve for all of them. High-speed digital camera, used to follow the fracture process during the instrumented impact test, revealed no significant change of the small scale yielding fracture process with increasing MFI. This was in an agreement with the negligible change in the size of the crack tip plastic zone, R_p, predicted using simple mixed mode fracture model. The plane strain value of the critical strain energy release rate, G_1c, calculated from the measured G_c for the INN (2.4 kJ/m²), UNI (2.8 kJ/m²) and SPH (3.5 kJ/m²) using a simple LEFM model did not exhibit significant dependence on the number of extruder passes. The observed differences between the three ICPPs were ascribed to the significantly larger EPR content in UNI compared to the other two ICPPs and significantly larger content of isotactic PP homopolymer in the INN compared to the remaining two ICPPs.     

Radiolabeling of HER2-specific Affibody molecule with F-18

The presence of human epidermal growth factor type 2 (HER2) on 20-30% of human breast cancer is a prognostic indicator of more rapid disease progression and a therapeutic indicator for anti-HER2 monoclonal antibodies. Because the literature has demonstrated some discordance between primary and metastatic tumors in the same patient for expression of the HER2 marker, we set out to develop an imaging agent that could be used to assess the marker concentration in vivo in an individual patient. The pharmaceutical company Affibody^® AB has optimized the specificity of Affibody^® molecules for HER2. Two Affibody^® molecules, a 7 kDa and an 8 kDa protein, were designed with a single carboxy terminal cysteine in order to provide a specific location for the purposes of labeling for various types of imaging. We have prepared [¹⁸F]FBEM utilizing a coupling reaction between [¹⁸F]fluorobenzoic acid and aminoethylmaleimide. We then optimized the conjugation of this radiolabeled maleimide to the free sulfhydryl of cysteine by incubating at pH 7.4 in phosphate buffered saline containing 0.1% sodium ascorbate. An overall uncorrected yield of radiolabeled Affibody^® molecule of approximately 10% from [¹⁸F]fluoride was achieved in a 2 h synthesis. These conjugated Affibody^® molecules were obtained with a specific activity of 2.51 ± 0.92 MBq/μg. Characterization of the product by HPLC-MS supported the conjugation of [¹⁸F]FBEM with the Affibody^® molecule. The radiolabeled Affibody^® molecule retained its binding specificity as demonstrated by successful imaging of xenografts expressing HER2.     

The rheology of Torlon solutions and its role in the formation of ultra-thin defect-free Torlon hollow fiber membranes for gas separation

Fundamental understanding of the material science and rheological engineering to fabricate Torlon^® 4000T-MV and 4000TF hollow fiber membranes with an ultra-thin and defect-free dense-selective layer for gas separation has been revealed. We have firstly investigated the rheology of Torlon^® 4000T-MV and 4000TF dope solutions, and then determined the effect of temperature-correlated shear and elongational viscosities on the formation of Torlon^® fibers for gas separation. Interestingly, Torlon^® 4000T-MV and 4000TF possess different rheological characteristics: the elongational viscosity of Torlon^® 4000T-MV/NMP solution shows strain thinning, while Torlon^® 4000TF/NMP solution shows strain hardening. The balanced viscoelastic properties of dope solutions, which are strongly dependent on the spinning temperature, have been found to be crucial for the formation of a defect-free dense layer. The optimum rheological properties to fabricate Torlon^® 4000T-MV/NMP hollow fibers appear at about 48–50 °C, and the resultant fibers have an O₂/N₂ selectivity of 8.37 and an apparent dense layer thickness of 781 Å. By comparison, the best Torlon^® 4000TF fibers were spun at 24 °C with an O₂/N₂ selectivity of 8.96 and a dense layer of 1116 Å. The CO₂/CH₄ selectivity of the above two Torlon^® variants is 47 and 53.5, respectively.     

Enhanced capabilities of separation in Sequential Injection Chromatography--fused-core particle column and its comparison with narrow-bore monolithic column

In the Sequential Injection Chromatography (SIC) only monolithic columns for chromatographic separations have been used so far. This article presents the first use of fused-core particle packed column in an attempt to extend of the chromatographic capabilities of the SIC system. A new fused-core particle column (2.7 μm) Ascentis^® Express C18 (Supelco™ Analytical) 30 mm × 4.6 mm brings high separation efficiency within flow rates and pressures comparable to monolithic column Chromolith^® Performance RP-18e 100-3 (Merck^®) 100 mm × 3 mm. Both columns matches the conditions of the commercially produced SIC system - SIChrom™ (8-port high-pressure selection valve and medium-pressure Sapphire™ syringe pump with 4 mL reservoir - maximal work pressure 1000 PSI) (FIAlab^®, USA). The system was tested by the separation of four estrogens with similar structure and an internal standard - ethylparaben. The mobile phase composed of acetonitrile/water (40/60 (v/v)) was pumped isocratic at flow rate 0.48 mL min⁻¹. Spectrophotometric detection was performed at wavelength of 225 nm and injected volume of sample solutions was 10 μL. The chromatographic characteristics of both columns were compared. Obtained results and conclusions have shown that both fused-core particle column and longer narrow shaped monolithic column bring benefits into the SIC method.     

EPR and Mössbauer characterization of RTV polysiloxane foams and their constituents

We have used electron paramagnetic resonance (EPR) and ⁵⁷Fe Mössbauer spectroscopies to investigate potential aging mechanisms in filled RTV polysiloxane foams, diatomaceous earth, and their other constituents. Intense, broad EPR resonances in the RTV foams were recorded at room temperature as a function of microwave power. These signals were shown to come from the diatomaceous earth filler (Celite^® 350) in the RTV foams. ⁵⁷Fe Mössbauer measurements for neat Celite^® 350 showed the presence of iron compounds in the form of lepidocrocite. Further EPR measurements showed that the intense, broad signals from Celite^® 350 and the RTV foams were due to lepidocrocite that has been annealed to 175 °C and is in an excited state. EPR measurements of annealed samples of Celite^® 350 also indicated that structural (chemisorbed) water is not easily released by the lepidocrocite. Therefore, the presence of intermediate forms of iron oxides in Celite^® 350 and RTV foams indicates that water is not active in these materials.     

Charging of Polycarbonate Films in a Direct-Current Discharge

The effect of treatment of Diflon, Makrolon^®, and Lexan^® polycarbonate films in the cathode fall of a dc discharge was studied. Plasma treatment was shown to result in the hydrophilization of the film surface. The dependence of the contact angle on the discharge current and treatment time was examined. It was found that the discharge induced a negative charge on the polycarbonate surface. The surface-charge density was correlated with the contact angle for various treatment conditions. Space charging processes in glow discharge-treated films were investigated using the thermally stimulated relaxation and depolarization techniques. The role of produced charged entities in an increase in the surface energy of modified polycarbonate films was revealed.