Explore the vast range of titles available.

The contamination of aquatic ecosystems with microplastics has recently been reported through many studies, and negative impacts on the aquatic biota have been described. For the chemical identification of microplastics, mainly Fourier transform infrared (FTIR) and Raman spectroscopy are used. But up to now, a critical comparison and validation of both spectroscopic methods with respect to microplastics analysis is missing. To close this knowledge gap, we investigated environmental samples by both Raman and FTIR spectroscopy. Firstly, particles and fibres >500 μm extracted from beach sediment samples were analysed by Raman and FTIR microspectroscopic single measurements. Our results illustrate that both methods are in principle suitable to identify microplastics from the environment. However, in some cases, especially for coloured particles, a combination of both spectroscopic methods is necessary for a complete and reliable characterisation of the chemical composition. Secondly, a marine sample containing particles <400 μm was investigated by Raman imaging and FTIR transmission imaging. The results were compared regarding number, size and type of detectable microplastics as well as spectra quality, measurement time and handling. We show that FTIR imaging leads to significant underestimation (about 35 %) of microplastics compared to Raman imaging, especially in the size range <20 μm. However, the measurement time of Raman imaging is considerably higher compared to FTIR imaging. In summary, we propose a further size division within the smaller microplastics fraction into 500–50 μm (rapid and reliable analysis by FTIR imaging) and into 50–1 μm (detailed and more time-consuming analysis by Raman imaging). Graphical Abstract Marine microplastic sample (fraction <400 μm) on a silicon filter (middle) with the corresponding Raman and IR images

Self-assembly of amphiphilic block copolymers into polymersomes continues to be a hot topic in modern research on biomimetics. Their well-known and valued mechanical strength can be increased even further if they are cross-linked. These additional bonds prevent a collapse or disassembly of the polymersomes and open the way towards smart nanoreactors. A variety of chemistries have been applied to obtain the desired cross-linked polymersomes, and therefore, the chemical approaches performed over time will be highlighted in this mini-review. Due to the large number of studies, a selected set of photo-cross-linked and pH-sensitive polymersomes will be specifically highlighted. This system has proven to be a very potent candidate for the formation of nanoreactors and drug delivery systems, and even for the formation of functional multicompartment cell mimics.

Effective recycling of polymers into valuable resources is the basis for establishing a circular economy. Whereas mechanical recycling often leads to downcycling, the concept of recycling‐on‐demand (ROD) has high promise. The aim is to design next‐generation polymer materials that combine good material properties during use with convenient recycling abilities into higher‐value building blocks at the end of use. This work targets oligomers as desired degradation products to enhance energy efficiency in degradation and re‐polymerization steps. Therefore, selectively cleavable bonds are implemented into polyesters to degrade them by application of certain triggers. Poly(ester‐co‐acetal)s (PEAs) with model character are synthesized in a solution‐based sustainable process utilizing organo‐catalysis. In this approach, OH‐terminated oligoesters (OEs) are bridged by acid‐labile acetal groups, yielding polymeric materials that provide excellent recyclability. Two degradation‐repolymerization cycles by formation and cleavage of the acetal bonds were verified by nuclear magnetic resonance spectroscopy. At the same time, size exclusion chromatography confirms the effective polymerization and selective degradation of the acetals under full retention of the polyester oligomers. Additionally, the OH number of the degraded materials is determined to ensure good stoichiometry for effective repolymerization. These combined efforts result in an impressive proof of concept for the proposed ROD principle. Recycling‐on‐demand (ROD) of polymers into valuable oligomeric building blocks introduces an important step toward a circular economy. Here, poly(ester‐co‐acetal)s (PEAs) serve as a representative model system demonstrating a full proof of concept for the proposed ROD procedure, where the original oligoester is fully retained after degradation and successfully re‐polymerized.

The presence of microplastics in aquatic ecosystems is a topical problem and leads to the need of appropriate and reliable analytical methods to distinctly identify and to quantify these particles in environmental samples. As an example transmission, Fourier transform infrared (FTIR) imaging can be used to analyze samples directly on filters without any visual presorting, when the environmental sample was afore extracted, purified, and filtered. However, this analytical approach is strongly restricted by the limited IR transparency of conventional filter materials. Within this study, we describe a novel silicon (Si) filter substrate produced by photolithographic microstructuring, which guarantees sufficient transparency for the broad mid-infrared region of 4000–600 cm⁻¹. This filter type features holes with a diameter of 10 μm and exhibits adequate mechanical stability. Furthermore, it will be shown that our Si filter substrate allows a distinct identification of the most common microplastics, polyethylene (PE), and polypropylene (PP), in the characteristic fingerprint region (1400–600 cm⁻¹). Moreover, using the Si filter substrate, a differentiation of microparticles of polyesters having quite similar chemical structure, like polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), is now possible, which facilitates a visualization of their distribution within a microplastic sample by FTIR imaging. Finally, this Si filter can also be used as substrate for Raman microscopy—a second complementary spectroscopic technique—to identify microplastic samples.

Defects in cellular protein/enzyme encoding or even in organelles are responsible for many diseases. For instance, dysfunctional lysosome or macrophage activity results in the unwanted accumulation of biomolecules and pathogens implicated in autoimmune, neurodegenerative, and metabolic disorders. Enzyme replacement therapy (ERT) is a medical treatment that replaces an enzyme that is deficient or absent in the body but suffers from short lifetime of the enzymes. Here, this work proposes the fabrication of two different pH‐responsive and crosslinked trypsin‐loaded polymersomes as protecting enzyme carriers mimicking artificial organelles (AOs). They allow the enzymatic degradation of biomolecules to mimic simplified lysosomal function at acidic pH and macrophage functions at physiological pH. For optimal working of digesting AOs in different environments, pH and salt composition are considered the key parameters, since they define the permeability of the membrane of the polymersomes and the access of model pathogens to the loaded trypsin. Thus, this work demonstrates environmentally controlled biomolecule digestion by trypsin‐loaded polymersomes also under simulated physiological fluids, allowing a prolonged therapeutic window due to protection of the enzyme in the AOs. This enables the application of AOs in the fields of biomimetic therapeutics, specifically in ERT for dysfunctional lysosomal diseases. A biomimetic contribution to the restoration of cellular or organelle functions by using therapeutic enzymes and to the enhancement of the limited lifetime of naked enzymes. Macrophage‐ and lysosome‐like functions are imitated by the use of trypsin‐loaded polymersomes in the pH range 7.5–6.5 for capturing and digesting enzymes as model pathogens by adjusting membrane properties.

For thermoelectric applications, both p- and n-type semi-conductive materials are combined. In melt-mixed composites based on thermoplastic polymers and carbon nanotubes, usually the p-type with a positive Seebeck coefficient (S) is present. One way to produce composites with a negative Seebeck coefficient is to add further additives. In the present study, for the first time, the combination of single-walled carbon nanotubes (SWCNTs) with polyvinylpyrrolidone (PVP) in melt-mixed composites is investigated. Polycarbonate (PC), poly(butylene terephthalate) (PBT), and poly(ether ether ketone) (PEEK) filled with SWCNTs and PVP were melt-mixed in small scales and thermoelectric properties of compression moulded plates were studied. It could be shown that a switch in the S-value from positive to negative values was only possible for PC composites. The addition of 5 wt% PVP shifted the S-value from 37.8 µV/K to −31.5 µV/K (2 wt% SWCNT). For PBT as a matrix, a decrease in the Seebeck coefficient from 59.4 µV/K to 8.0 µV/K (8 wt% PVP, 2 wt% SWCNT) could be found. In PEEK-based composites, the S-value increased slightly with the PVP content from 48.0 µV/K up to 54.3 µV/K (3 wt% PVP, 1 wt% SWCNT). In addition, the long-term stability of the composites was studied. Unfortunately, the achieved properties were not stable over a storage time of 6 or 18 months. Thus, in summary, PVP is not suitable for producing long-term stable, melt-mixed n-type SWCNT composites.

Enhancing both ionic conductivity and mechanical robustness remains a major challenge in designing solid-state electrolytes for lithium batteries. This work presents a novel approach in designing mechanically robust and highly conductive solid-state electrolytes, which involves ionic liquid-based cross-linked polymer networks incorporating polymeric ionic liquids (PILs). First, linear PILs with different side groups were synthesized for optimizing the structure. Molecular weights of the PIL samples, ranging from 30 to 40 kDa, were determined using a complimentary combination of thermal field-flow fractionation (ThFFF) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis. The aimed for networks were synthesized through the photo-initiated polymerization of a network-forming monomer and a cross-linker, in the presence of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and a PIL bearing quaternized imidazolium groups. The resulting cross-linked membranes - semi-interpenetrating networks - exhibit substantial mechanical strength, with a Young's modulus of 40-50 MPa, surpassing the threshold for solid-state battery separators, while maintaining high ionic conductivity in the range of 4 × 10 −4 S·cm −1 at 60°C. Notably, the introduction of oligo(ethylene glycol) moieties into the PIL structure significantly enhances ionic conductivity and allows for incorporation of a larger amount of the lithium salt compared to the alkyl-substituted analogs. Moreover, although cross-linking often impairs ionic transport as a result of restricted segmental mobility of the polymer chains, incorporation into the network of highly conductive linear PILs circumvents this issue. This unique combination of properties positions the developed membranes as promising candidates for application in solid-state lithium batteries, effectively addressing the traditional trade-off in electrolyte design.

This study presents a mechanoresponsive star‐shaped BCP synthesized using a 3‐arm‐rhodamine‐based ATRP initiator. The star rhodamine mechanophore was employed to construct a 3‐arm star poly(butyl acrylate)‐b‐poly(methyl methacrylate) (PBA‐b‐PMMA) BCP, alongside random star copolymers and a linear BCP for comparison. Structural characterization via NMR, SEC, and FT‐IR confirmed the successful synthesis, while DSC, AFM, and SAXS analyses revealed distinct phase separation in the BCP structures, which results in enhanced mechanical strength and features of thermoplastic elastomers in the materials. Interestingly, the synthesized mechanoresponsive tri‐arm star and bi‐arm linear architectures in both block and random copolymer configurations exhibited a switch‐off state in solution but transitioned to a “switch‐on” state in the film form due to internal strain‐induced mechanophoric activation. Once activated in the film state, the fluorescence intensity increases with increasing stretching, indicating progressive mechanophore activation under mechanical stress, however, with a complete and precise peak shift is only observed for the star BCP architecture. This allows, uniquely in the block copolymers architecture with the mechanophoric unit in the core, a precise determination of additional stress on the material after processing. The study provides new insight into the mechanochemical activation of rhodamine‐based systems and highlights the role of molecular architecture and processing state in governing mechanoresponse. Mechanoresponsive rhodamine containing linear and star block and random copolymers were synthesized and characterized. All materials transitioned into a “switch‐on” state in the film form, but only the star block copolymer architecture exhibited a complete and precise peak shift upon stretching, providing new insights into the mechanochemical activation of rhodamine‐based systems and highlights the role of molecular architecture and processing state in governing mechanoresponse.

Understanding the diffusion of nanoparticles through permeable membranes in cell mimics paves the way for the construction of more sophisticated synthetic protocells with control over the exchange of nanoparticles or biomacromolecules between different compartments. Nanoparticles postloading by swollen pH switchable polymersomes is investigated and nanoparticles locations at or within polymersome membrane and polymersome lumen are precisely determined. Validation of transmembrane diffusion properties is performed based on nanoparticles of different origin—gold, glycopolymer protein mimics, and the enzymes myoglobin and esterase—with dimensions between 5 and 15 nm. This process is compared with the in situ loading of nanoparticles during polymersome formation and analyzed by advanced multiple‐detector asymmetrical flow field‐flow fractionation (AF4). These experiments are supported by complementary i) release studies of protein mimics from polymersomes, ii) stability and cyclic pH switches test for in polymersome encapsulated myoglobin, and iii) cryogenic transmission electron microscopy studies on nanoparticles loaded polymersomes. Different locations (e.g., membrane and/or lumen) are identified for the uptake of each protein. The protein locations are extracted from the increasing scaling parameters and the decreasing apparent density of enzyme‐containing polymersomes as determined by AF4. Postloading demonstrates to be a valuable tool for the implementation of cell‐like functions in polymersomes. For integrating cell‐like functions in polymersomes, control over nanoparticle locations (membrane, lumen of polymersomes, and/or inner/outer membrane surface) is demonstrated by a postloading approach of swollen polymersomes. The softness of nanoparticles for crossing polymersomes membrane is the major key issue, while the size and charge of nanoparticles mainly plays a minor role.

The interest in bio‐based alternatives to classical polyesters such as poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) is steadily growing to achieve a more sustainable approach to polymer materials. In this study, PBT/poly(butylene furanoate) (PBF) blends are prepared, characterized and extrusion foamed. PBF as a bio‐based polyester offers two advantages. The ecological footprint of the material is reduced, and additionally, it can be used in Diels‐Alder reactions at the blend surface to support fusion of the foamed beads. The blending behavior of the polyesters is investigated using samples prepared in a microcompounder, particularly focused on the miscibility of the blends and transesterification reactions. The blends are thermodynamically immiscible but show a certain degree of transesterification according to nuclear magnetic resonance (NMR) spectroscopy. The morphology of blend beads produced by an extrusion foaming process is analyzed regarding their cell density, cell size distribution, and open‐cell content. It is shown that PBF has a positive effect on the bead foam morphology. The use of a bifunctional linker designed for chemical fusion of the bead surfaces allows to obtaining of molded parts, in contrast to beads containing pure PBT.