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- ItemFe3O4 Nanoparticles Grown on Cellulose/GO Hydrogels as Advanced Catalytic Materials for the Heterogeneous Fenton-like Reaction(Washington, DC : ACS Publications, 2019) Chen, Yian; Pötschke, Petra; Pionteck, Jürgen; Voit, Brigitte; Qi, HaisongCellulose/graphene oxide (GO)/iron oxide (Fe3O4) composites were prepared by coprecipitating iron salts onto cellulose/GO hydrogels in a basic solution. X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared, and X-ray diffraction characterization showed that Fe3O4 was successfully coated on GO sheets and cellulose. Cellulose/GO/Fe3O4 composites showed excellent catalytic activity by maintaining almost 98% of the removal of acid orange 7 (AO7) and showed stability over 20 consecutive cycles. This performance is attributable to the synergistic effect of Fe3O4 and GO during the heterogeneous Fenton-like reaction. Especially, the cellulose/GO/Fe3O4 composites preserve their activity by keeping the ratio of Fe3+/Fe2+ at 2 even after 20 catalysis cycles, which is supported by XPS analysis.
- ItemSemi-Interpenetrating Polymer Networks Based on N-isopropylacrylamide and 2-acrylamido-2-methylpropane Sulfonic Acid for Intramolecular Force-Compensated Sensors(Bristol : IOP Publishing, 2021) Binder, Simon; Zschoche, Stefan; Voit, Brigitte; Gerlach, GeraldStimulus-responsive hydrogels are swellable polymers that take up a specific volume depending on a measured variable present in solution. Hydrogel-based chemical sensors make use of this ability by converting the resulting swelling pressure, which depends on the measured variable, into an electrical value. Due to the tedious swelling processes, the measuring method of intramolecular force compensation is used to suppress these swelling processes and, thus, significantly increase the sensor's response time. However, intramolecular force compensation requires a bisensitive hydrogel. In addition to the sensitivity of the measured variable the gel has to provide a second sensitivity for intrinsic compensation of the swelling pressure. At the same time, this hydrogel has to meet further requirements, e.g. high compressive strength. Until now, interpenetrating polymer networks (IPN) have been used for such a force-compensatory effective hydrogel, which are complex to manufacture. In order to significantly simplify the sensor design and production, a simpler synthesis of the bisensitive hydrogel is desirable. This paper presents a new bisensitive hydrogel based on semi-interpenetrating polymer networks. It is based on a copolymer network consisting of N-isopropylacrylamide (NiPAAm) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) and long PAMPS strands that permeate it. Measurements show, that this hydrogel meets all essential requirements for intramolecular force compensation and is at the same time much easier to synthesize than previously used IPN hydrogels. © 2021 The Author(s).
- ItemSynthesis and characterization of poly(1,2,3-triazole)s with inherent high sulfur content for optical applications(Hoboken, NJ : Wiley, 2023) Mazumder, Kajari; Komber, Hartmut; Bittrich, Eva; Voit, Brigitte; Banerjee, SusantaThe synthesis of solution-processable sulfur-containing polytriazoles for optoelectronic applications is a relatively less explored domain in polymer research. The synthesis of novel bifunctional (DA) and trifunctional (TA) azido-monomers with inherent high sulfur content and of organo-soluble high refractive index poly(1,2,3-triazole)s using the azido-monomers via Cu(I) assisted click polymerization reactions are reported in this work. The azido-monomers were synthesized by the conversion of previously reported amine-functionalized compounds to azides using azidotrimethylsilane in a polar aprotic solvent. Dialkyne monomers were also synthesized and reacted with the azides to prepare a series of five linear and two hyperbranched poly(1,2,3-triazole)s. Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, differential scanning calorimetry and thermogravimetric analysis were used to characterize the synthesized polymers. It was also demonstrated that the use of the trifunctional azide in optimized conditions resulted in increased solubility of an otherwise insoluble linear poly(1,2,3-triazole). The optical characterization of the polymers was carried out on thin polymer films with thickness in the nanometer range, which were successfully prepared by spin-coating on silicon wafers. It was found that the increase in the sulfur and aromatic content in the polymer backbone successfully increased the refractive index of the polymers up to 1.743 at 589 nm.
- ItemInfluence of different carbon nanotubes on the electrical and mechanical properties of melt mixed poly(ether sulfone)-multi walled carbon nanotube composites(Barking : Elsevier, 2012) Chakraborty, Sourav; Pionteck, Jürgen; Krause, Beate; Banerjee, Susanta; Voit, BrigitteCommercial Udel® poly(ether sulfone) (PSU) was filled with three different commercially available multiwalled carbon nanotubes (MWCNTs) by small scale melt mixing. The MWCNTs were as grown NC 7000 and two of its derivatives prepared by ball milling treatment. One of them was unmodified (NC 3150); the other was amino modified (NC 3152). The main difference beside the reactivity was the reduced aspect ratio of NC 3150 and NC 3152 caused by ball milling process. All PSU/MWCNT composites with similar filler content were prepared under fixed processing conditions and comparative analysis of their electrical and mechanical properties were performed and were correlated with their microstructure, characterized by optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A non-uniform MWCNT dispersion was observed in all composites. The MWCNTs were present in form of agglomerates in the size of 10-60. μm whereas the deagglomerated part was homogeneously distributed in the PSU matrix. The differences in the agglomeration states correlate with the variations of properties between different PSU/MWCNT composites. The lowest electrical percolation threshold of 0.25-0.5. wt.% was observed for the shortened non-functionalized MWCNT composites and the highest for amine-modified MWCNT composites (ca. 1.5. wt.%). The tensile behavior of the three composites was only slightly altered with CNT loading as compared to the pure PSU. However, the elongation at break showed a reduction with MWCNT loading and the reduction was least for composite with best MWCNT dispersion. © 2012 Elsevier Ltd.