Temperature-dependent rheological and viscoelastic investigation of a poly(2-methyl-2oxazoline)-b-poly(2-iso-butyl-2-oxazoline)-b-poly(2-methyl-2-oxazoline)-based thermogelling hydrogel

The synthesis and characterization of an ABA triblock copolymer based on hydrophilic poly(2-methyl-2-oxazoline) (pMeOx) blocks A and a modestly hydrophobic poly(2-iso-butyl-2-oxazoline) (piBuOx) block B is described. Aqueous polymer solutions were prepared at different concentrations (1–20 wt %) and their thermogelling capability using visual observation was investigated at different temperatures ranging from 5 to 80 ◦C. As only a 20 wt % solution was found to undergo thermogelation, this concentration was investigated in more detail regarding its temperature-dependent viscoelastic profile utilizing various modes (strain or temperature sweep). The prepared hydrogels from this particular ABA triblock copolymer have interesting rheological and viscoelastic properties, such as reversible thermogelling and shear thinning, and may be used as bioink, which was supported by its very low cytotoxicity and initial printing experiments using the hydrogels. However, the soft character and low yield stress of the gels do not allow real 3D printing at this point. © 2019 by the authors.Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)German Research Foundation (DFG) [326998133-TRR 225, 398461692]; Evonik Foundation; Ministry of Education, Youth and Sports of the Czech Republic-program NPU I [LO1504]; Deutsche Forschungsgemeinschaft within the DFG State Major Instrumentation ProgrammeGerman Research Foundation (DFG) [INST 105022/58-1 FUGG

Anti-corrosive and oil sensitive coatings based on epoxy/polyaniline/magnetite-clay composites through diazonium interfacial chemistry

Epoxy polymer nanocomposites filled with magnetite (Fe3O4) clay (B), named (B-DPA-PANI@Fe3O4) have been prepared at different filler loading (0.1, 0.5, 1, 3, 5 wt. %). The surface modification of clay by polyaniline (PANI) is achieved in the presence of 4-diphenylamine diazonium salt (DPA). The effects of the nanofiller loading on Tensile, mechanical and dielectric properties were systematically studied. Improved properties was highlighted for all reinforced samples. The addition of only 3 wt. % of the filler enhanced the tensile strength of the composites by 256%, and the glass transition temperature Tg by 37%. The dielectric spectra over a broad frequency showed a robust interface between the hybrid (B-DPA-PANI@Fe3O4) fillers and epoxy matrix. The results showed most significant improvement in corrosion inhibition using electrochemical impedance spectroscopy (EIS) in 3.5 wt % NaCl, as well as a significant response in oil sensing test. High charge transfer resistance of 110 × 106 Ω.cm2 using 3-wt % of filler was noted compared to 0.35 × 106 Ω.cm2 for the pure epoxy. The results obtained herein will open new routes for the preparation of efficient anticorrosion sensor coatings. © 2018, The Author(s).NPRP Award from the Qatar National Research Fund (a member of Qatar Foundation) [8-878-1-172

Vibration sensing systems based on poly(Vinylidene fluoride) and microwave-assisted synthesized zno star-like particles with controllable structural and physical properties

This study deals with the effect of zinc oxide (ZnO) star-like filler addition to the poly(vinylidene fluoride) (PVDF) matrix, and its effect on the structural and physical properties and consequences to the vibration sensing performance. Microwave-assisted synthesis in open vessel setup was optimized for the preparation of the star-like shape of ZnO crystalline particles. The crystalline and star-like structure was confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDX). Furthermore, the PVDF-based composites were prepared using a spin-coating technique from solution. An investigation of the transformation of the α crystalline phase to the β crystalline phase of the neat PVDF matrix and with various filler concentrations was performed using Fourier-Transform infrared (FTIR) spectroscopy, which shows an enhanced β-phase from 44.1% to 66.4% for neat PVDF and PVDF with 10 wt.% of particles, respectively. Differential scanning calorimetry (DSC) measurements and investigation showed enhanced crystallinity and melting enthalpy of the composite systems in comparison to neat PVDF, since ZnO star-like particles act as nucleating agents. The impact of the filler content on the physical properties, such as thermal and dynamic mechanical properties, which are critical for the intended applications, were investigated as well, and showed that fabricated composites exhibit enhanced thermal stability. Because of its dynamic mechanical properties, the composites can still be utilized as flexible sensors. Finally, the vibration sensing capability was systematically investigated, and it was shown that the addition of ZnO star-like filler enhanced the value of the thickness mode d33 piezoelectric constant from 16.3 pC/N to 29.2 pC/N for neat PVDF and PVDF with 10 wt.% of ZnO star-like particles. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Qatar National Research Fund (a member of the Qatar Foundation) [NPRP-6-282-2-119]; Czech Science FoundationGrant Agency of the Czech Republic [19-17457S]; Ministry of Education, Youth and Sports of the Czech Republic-DKRVO [RP/CPS/2020/003

The implication of PMMA molecular weight on compatibility of SAN/PMMA blends containing GO-g-PMMA hybrid compatibilizers

The molecular weight of a polymer is one of the most important factors defining material properties and performance. Within the current study, poly(styrene-co-acrylonitrile)/poly(methyl methacrylate) (SAN/PMMA) blends containing hybrid particles of graphene oxide-g-poly(methyl methacrylate) (GO-g-PMMA) were designed so that the molecular weight of the PMMA chains tethered on the GO particles was correlated with the molecular weight of the PMMA matrix. Hybrid particles were prepared using surface-initiated atom transfer radical polymerization (ATRP). The number average molecular weight of the matrix PMMA was Mn = 20,100 or 130,900 g/mol, while in the case of hybrids it was Mn = 5600, 27,300 or 191,600 g/mol. Two blend compositions were investigated: SAN/PMMA= 70/30 and 90/10 wt/wt, and the content of GO-g-PMMA was 1 wt%. Based on rheological studies it was demonstrated that higher molecular weights of the matrix PMMA promoted the compatibility of SAN/PMMA due to the similar viscosity of both blend components. Furthermore, the length of the PMMA chains grafted to the GO influenced the viscoelastic response of the material, resulting in different relaxation behavior as confirmed by mean relaxation times calculated from Cole-Cole plots. In addition, the effect of neat GO and GO-g-PMMA particles on the blend morphology and size distribution of PMMA droplets was discussed based on rheology and TEM analyses.DKRVO, (RP/CPS/2022/003); Doctoral Candidate in the Interdisciplinary Doctoral School at the Lodz University of Technology; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠM

Influence of PMMA brushes grafted from GO on rheological properties of PMMA/SAN immiscible blend in shear and elongation flow

In real technological processes, both shear and elongational flow is present. The material properties may differ significantly under both types of flow. Hence, they both define the final morphology and thus properties of the materials. In this work, the morphology of immiscible blends containing polymer hybrid particles was related to extensional rheological properties for the first time. The effect of various lengths of polymer brushes grafted from graphene oxide particles (GO) surface was investigated. As a polymer matrix the immiscible blend of poly(methyl methacrylate)/styrene-co-acrylonitrile (PMMA/SAN) was used. Thus the poly(methyl methacrylate) (PMMA) brushes grafted from GO (GO-g-PMMA) with various number average molar masses (Mn) of PMMA brushes with respect to chain entanglement limit of freely dispersed PMMA were prepared. The extensional rheological properties were affected by Mn of PMMA brushes, while the rheological properties in shear were unchanged. Transmission electron microscopy revealed the compatibilization effect for short densely grafted brushes with Mn of 10,300 g/mol, as smaller domains were observed. On the contrary, the higher Mn PMMA brushes facilitated coalescence. With increasing length of brushes, the elongational viscosity at low elongation rates (∼ 0.1 s−1) was not sufficient enough to cause fiber breakup and thus elongated domains were formed.665778; Slovenská Akadémia Vied, SAV: 313021T081; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: RP/CPS/2022/003; Narodowe Centrum Nauki, NCN: UMO-2016/23/P/ST5/02131; Vedecká Grantová Agentúra MŠVVaŠ SR a SAV, VEGA: 2/0137/23; European Regional Development Fund, ERDF: APVV-19-0338National Science Centre, Poland [UMO-2016/23/P/ST5/02131]; European Union [665778]; Ministry of Education, Youth and Sports of the Czech republic-DKRVO [RP/CPS/2022/003]; Integrated Infrastructure Operational Program - ERDF [313021T081]; [APVV-19-0338]; [VEGA 2/0137/23

The declining occurrence of moose ( Alces alces

The border region between Austria, the Czech Republic, and Germany harbors the most south-western occurrence of moose in continental Europe. The population originated in Poland, where moose survived, immigrated from former Soviet Union or were reintroduced after the Second World War expanded west and southwards. In recent years, the distribution of the nonetheless small Central European population seems to have declined, necessitating an evaluation of its current status. In this study, existing datasets of moose observations from 1958 to 2019 collected in the three countries were combined to create a database totaling 771 records (observations and deaths). The database was then used to analyze the following: (a) changes in moose distribution, (b) the most important mortality factors, and (c) the availability of suitable habitat as determined using a maximum entropy approach. The results showed a progressive increase in the number of moose observations after 1958, with peaks in the 1990s and around 2010, followed by a relatively steep drop after 2013. Mortality within the moose population was mostly due to human interactions, including 13 deadly wildlife-vehicle collisions, particularly on minor roads, and four animals that were either legally culled or poached. Our habitat model suggested that higher altitudes (ca. 700–1,000 m a.s.l.), especially those offering wetlands, broad- leaved forests and natural grasslands, are the preferred habitats of moose whereas steep slopes and areas of human activity are avoided. The habitat model also revealed the availability of large core areas of suitable habitat beyond the current distribution, suggesting that habitat was not the limiting factor explaining the moose distribution in the study area. Our findings call for immediate transboundary conservation measures to sustain the moose population, such as those aimed at preventing wildlife-vehicle collisions and illegal killings. Infrastructure planning and development activities must take into account the habitat requirements of moose.publishedVersio