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Donor–acceptor Stenhouse adducts (DASAs) are a rapidly emerging class of visible light‐activated photochromes and DASA‐functionalized polymers hold great promise as biocompatible photoresponsive materials. However, the photoswitching performance of DASAs in solid polymer matrices is often low, particularly in materials below their glass transition temperature. To overcome this limitation, DASAs are conjugated to polydimethylsiloxanes which have a glass transition temperature far below room temperature and which can create a mobile molecular environment around the DASAs for achieving more solution‐like photoswitching kinetics in bulk polymers. The dispersion of DASAs conjugated to such flexible oligomers into solid polymer matrices allows for more effective and tunable DASA photoswitching in stiff polymers, such as poly(methyl methacrylate), without requiring modifications of the matrix. The photoswitching of conjugates with varying polymer molecular weight, linker type, and architecture is characterized via time‐dependent UV–vis spectroscopy in organic solvents and blended into polymethacrylate films. In addition, DASA‐functionalized polydimethylsiloxane networks, accessible via the same synthetic route, provide an alternative solution for achieving fast and efficient DASA photoswitching in the bulk owing to their intrinsic softness and flexibility. These findings may contribute to the development of DASA‐functionalized materials with better tunable, more effective, and more reversible modulation of their optical properties. [ABSTRACT FROM AUTHOR]

Donor–acceptor Stenhouse adducts (DASAs) are visible‐light‐responsive photoswitches with a variety of emerging applications in photoresponsive materials. Their two‐step modular synthesis, centered on the nucleophilic ring opening of an activated furan, makes DASAs readily accessible. However, the use of less reactive donors or acceptors renders the process slow and low yielding, which has limited their development. We demonstrate here that 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) promotes the ring‐opening reaction and stabilizes the open isomer, allowing greatly reduced reaction times and increased yields for known derivatives. In addition, it provides access to previously unattainable DASA‐based photoswitches and DASA–polymer conjugates. The role of HFIP and the photochromic properties of a set of new DASAs is probed using a combination of 1H NMR and UV/Vis spectroscopy. The use of sterically hindered, electron‐poor amines enabled the dark equilibrium to be decoupled from closed‐isomer half‐lives for the first time. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Fruits and vegetables have increasingly been related to foodborne outbreaks. Besides surface contamination, a possible internalization of microorganisms into edible parts of plants during growth has already been observed. To examine an actual risk for the consumer, microbial contamination of the rind and pulp of 147 muskmelons from international trade was assessed using cultural and biochemical methods, polymerase chain reaction and matrix‐assisted laser desorption/ionization‐time of flight mass spectrometry. RESULTS: One hundred percent of the rind samples [3.69–8.92 log colony forming units (CFU) g−1] and 89.8% of the pulp samples (maximum load 3.66 log CFU g−1) were microbiologically contaminated. Among the 432 pulp isolates, opportunistic and potentially pathogenic bacteria were identified, mainly Staphylococcus spp. (48.9%), Clostridium spp. (42.9%) and Enterobacteriaceae (27.9%). Salmonella spp., Escherichia coli and isolates of the Bacillus cereus group were found on the rind (1.4%, 0.7% and 42.9%, respectively) and in the pulp (0.7%, 1.4% and 4.7%). Clostridium perfringens was isolated from the rind of seven melons. CONCLUSION: The present study revealed a regularly occurring internal contamination of melons. Possible health risks for consumers because of an occurrence of microorganisms in melon pulp should be considered in future food safety assessments. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The article presents an experimental method which demonstrates the fabrication of nanofibers using the linear fusion and magnetic self-assembly of magnetic polymer nanoparticles in an aqueous environment. It provides detailed analysis of the distribution and internal fiber morphology of magnetic particles by the transmission electron microscopy (TEM) imaging. Results show the preparation of inorganic and hybrid fibers and nanorods in aqueous dispersion.

The fluorescent dye 8‐hydroxypyrene‐1,3,6‐trisulfonate (pyranine) combines high photostability with ratiometric pH detection in the physiological range, making it a prime candidate for optical sensors in biomedical applications, such as pH‐based chronic wound monitoring. However, pyranine's high water solubility and the difficulty of covalent attachment pose severe limitations in terms of leaching from sensor matrices. Herein, pyranine‐modified nanophase‐separated amphiphilic polymer conetworks (APCNs) are reported as fluorescent ratiometric pH sensors. The thin, freestanding APCN membranes composed of one hydrophilic and one hydrophobic polymer provide an optically transparent, flexible, and stable ideal matrix that enables contact between dye and aqueous environment. An active ester‐based conjugation approach results in a highly homogeneous and stable pyranine modification of the APCN's hydrophilic phase. This concept effectively solves the leaching challenge for pyranine without compromising its functionality, which is demonstrated by ratiometric pH detection in the range of pH 5–9. [ABSTRACT FROM AUTHOR]