Microstructure, Physical and Biological Properties, and BSA Binding Investigation of Electrospun Nanofibers Made of Poly(AA-co-ACMO) Copolymer and Polyurethane.

In this study, poly(AA-co-ACMO) and polyurethane-based nanofibers were prepared in a ratio of 1:1 (NF11) and 2:1 (NF21) as antimicrobial carriers for chronic wound management. Different techniques were used to characterize the nanofibers, and poly(AA-co-ACMO) was mostly found on the surface of PU. With an increase in poly(AA-co-ACMO) dose from 0 (PU) and 1:1 (NF11) to 2:1 (NF21) in the casting solution, the contact angle (CA) was reduced from 137 and 95 to 24, respectively, and hydrophilicity was significantly increased. As most medications inhibit biological processes by binding to a specific protein, in vitro protein binding was investigated mechanistically using a stopped-flow technique. Both NF11 and NF21 bind to BSA via two reversible steps: a fast second-order binding followed by a slow first-order one. The overall parameters for NF11 (Ka = 1.1 × 104 M-1, Kd = 89.0 × 10-6, ΔG0 = -23.1 kJ mol-1) and NF21 (Ka = 189.0 × 104 M-1, Kd = 5.3 × 10-6 M, ΔG0 = -27.5 kJ mol-1) were determined and showed that the affinity for BSA is approximately (NF11)/(NF21) = 1/180. This indicates that NF21 has much higher BSA affinity than NF11, although BSA interacts with NF11 much faster. NF21 with higher hydrophilicity showed effective antibacterial properties compared to NF11, in agreement with kinetic data. The study provided an approach to manage chronic wounds and treating protein-containing wastewater.

Analysis of flame retardants and elements of concern in printed wiring boards with respect to origin and year of construction.

Thirty-one populated printed wiring boards, covering a range of 30 years of construction, and originating from various electronic devices, were investigated using different analytical procedures. Noble, precious and rare metals, as well as environmentally relevant elements were identified by EDXRF, and lead and the flame retardant (FR) indicator bromine were localised by means of microbeam EDXRF. A GC/MS procedure was developed to identify and quantify FR substances. Several sample preparation techniques were applied, optimised and compared. The method of first choice was ultrasonic extraction because it provided the best compromise between effort, cost and quality of the analytical results. Altogether, a wide variety of elements of concern, and halogenated and phosphate-based FRs were found in the investigated boards. Their occurrence is partially related to the origin and/or year of construction.

Preparation of reference materials for the determination of RoHS-relevant flame retardants in styrenic polymers.

Reference materials for the analysis of polybrominated diphenyl ethers, polybrominated biphenyls and other common brominated flame retardants (FR) in styrenic polymers were prepared to suit the demands of actual restriction of the use of certain hazardous substances in electrical and electronic equipment analytics. Three methods of preparation were employed, viz. pellet forming, dissolution/vaporisation and extrusion, whereby extrusion proved to be the most suitable method. For extrusion, three procedures of pre-mixing were investigated: the polymers were either mixed with FR powder, FR solutions or FR concentrates that were taken from waste industrial polymers. The latter procedure proved to be most appropriate in terms of analyte concentration, predictability and recovery. The homogeneity of the samples, as well as the chemical and thermal long-term stabilities, was investigated. The result was an optimised method to prepare a suitable reference material for laboratory use.

Heterogeneous electron transfer at Au/SAM junctions in a room-temperature ionic liquid under pressure.

Proven electrochemical approaches were applied to study heterogeneous electron transfer (ET) between selected redox couples and gold electrodes modified with alkanethiol self-assembled monolayers (SAMs), using the room-temperature ionic liquid (RTIL) [bmim][NTf2] as reaction medium; ferrocene as freely diffusing redox probe in the RTIL was tested for ET through both thin (butanethiol) and thick (dodecanethiol) assemblages at pressures up to 150 MPa; well behaved kinetic patterns and reproducibility of data were demonstrated for ET within the unique Au/SAM/RTIL arrays.

Versatile and fast gas chromatographic determination of frequently used brominated flame retardants in styrenic polymers.

Two versatile and fast methods to identify and quantify brominated flame retardants (BrFRs) in styrenic polymers were developed. Gas chromatography/mass spectrometry (GC/MS) as well as gas chromatography with electron-capture detection (GC/ECD), both following ultrasonic-supported dissolution and precipitation (USDP), were applied. The substance range includes poly-brominated biphenyls (PBBs) and diphenyl ethers (PBDEs), as well as other commonly used flame retardants (FRs), including two phosphate-based flame retardants. The methods were verified using congener standards and flame-retardant polymer samples. Good recoveries were found. Overall run time for the analysis, including sample preparation, is less than 60 min.

Characterisation of polymer fractions from waste electrical and electronic equipment (WEEE) and implications for waste management.

There is an increasing interest in the end-of-life management of polymers present in waste electrical and electronic equipment (WEEE). This is mainly due to high recycling and recovery quotas set by the European WEEE directive, which can only be fulfilled by including the plastic fraction in recycling and recovery approaches. Previous studies identified a high material diversity and various contaminants in WEEE plastics, including heavy metals, polybrominated biphenyls (PBB), diphenyl ethers (PBDE), as well as polybrominated dibenzodioxins and dibenzofurans (PBDD/F). These substances are regulated by European directives that limit their levels in marketable products. Consequently, both material diversity and contaminants are strong arguments against material recycling and point to hazardous waste treatment. However, recent developments in the production of flame retardants and electrical and electronic goods aimed to reduce contaminants and material diversity. Thus, the present study summarises updated contaminant levels of plastic fractions of European WEEE, as well as data on materials in waste housing polymers. Material characterisation revealed housing fractions to be interesting sources for polymer recycling, which however has to implement potent material separation and/or bromine elimination techniques. With respect to contaminants, our data indicate an effective phase-out of PBB, but still high levels of PBDE and PBDD/F are found. Sources and implications for the material recycling and thermal recovery approaches are discussed in detail.

Rapid identification of RoHS-relevant flame retardants from polymer housings by ultrasonic extraction and RP-HPLC/UV.

A rapid method was developed for the extraction and identification of RoHS-relevant organic flame retardants in polymer material. Extraction was carried out using ultrasonic supported solvent extraction (USSE) and isopropanol. HPLC separation was achieved using a reversed-phase phenylhexyl-modified column and methanol, containing 2-aminoethanol-buffered, alkaline water. Identification was carried out by scanning UV detection and comparison with a library assembled from spectra of reference substances. The method was used to extract and identify polymer additives in TV and PC monitor housings. The overall runtime required for extraction and chromatographic analysis is less than 10 min. The limits of detection comply with the recommendations set by the German draft law.

Gas chromatographic determination of phosphate-based flame retardants in styrene-based polymers from waste electrical and electronic equipment.

Two methods for the determination of phosphate-based flame retardants (PFRs) and similar organophosphates (OPs) were developed. Two gas chromatographic systems were applied, one equipped with a quadrupole mass spectrometer (GC/MS), the other with a specific phosphorus-nitrogen detector (GC/PND). A procedure of ultrasonic supported extraction and precipitation (USSE) was applied and verified using in-house produced reference materials. Twelve polymer parts of electrical and electronic devices, and eight polymer references were analysed for their PFR contents. The results show that the methods are capable of identifying PFRs in concentration ranges from 3 µg L(-1) (tricresyl phosphate, TCP) to 12 µg L(-1) (cresyl diphenyl phosphate, CDP) on GC/PND and from 110 µg L(-1) (triphenyl phosphine oxide, TPPO) to 3250 µg L(-1) (tris(ethylhexyl) phosphate, TEHP) on GC/MS in reference solutions. LODs in polymer extracts range from 180 µg g(-1) (triphenyl phosphate, TPP) to 670 µg g(-1) (bisphenol-A-bis(diphenyl phosphate), BDP) on GC/PND and from 75 µg g(-1) (TPPO) to 780 µg g(-1) (BDP) on GC/MS. The overall procedure time for one sample was less than 45 min (GC/MS) and less than 65 min (GC/PND).

Electrostatic complexation and photoinduced electron transfer between Zn-cytochrome c and [olyanionic fullerene dendrimers.

Two dendritic fullerene (DF) monoadducts, 2 and 3, which can carry up to 9 and 18 negative charges, respectively, were examined with respect to electrostatic complexation with Cytochrome c (Cytc). To facilitate comprehensive photophysical investigations, the zinc analogue of Cytc (ZnCytc) was prepared according to a novel, modified procedure. The association of ZnCytc and DF, and consequential photoinduced electron transfer within ZnCytc-DF from the photoexcited protein to the fullerene, was proven by fluorescence spectroscopy and transient absorption spectroscopy. These findings were also supported by circular dichroism as well as by extensive molecular dynamics (MD) simulations.