Whether or not hyperbranched polymers behave like quasi “hard spheres” in solution is the subject of numerous fundamental discussions, also motivated by research on the perfectly branched dendrimer ...structures. Experimentally targeting this question, a homologous series of hyperbranched polyglycerols (HPGs) was prepared in a wide range of molar masses from ca. 3000 to 700000 g mol–1 and an overall degree of branching (DB) between 0.55 and 0.59. HPG samples have been investigated by a comprehensive set of experimental hydrodynamic and light scattering approaches, i.e., sedimentation velocity studies in analytical ultracentrifugation, dynamic and static light scattering experiments, isothermal diffusion experiments, intrinsic viscosities, and size exclusion chromatography coupled with multiangle laser light scattering. The physical soundness of the obtained average molar masses, evaluated by the different, arguably, absolute approaches to molar mass estimations was verified via the concept of the hydrodynamic invariant (A 0). The A 0 values for the here studied and literature available/calculated values for all types of branched macromolecular topologies were found to assume an average of A 0 = (2.6 ± 0.4) × 10–10 g cm2 s–2 K–1 mol–1/3. The hyperbranched polyglycerols adopt a very compact, globular-like conformation in aqueous solution, which is accompanied by a very high level of hydration, on average 1.7 g of water per 1 g of HPG macromolecules. The correspondingly determined classical scaling relationships return values that are characteristic for a classical hard sphere conformation: s = 2.16 × 10–3 M 0.67, S, D = 251 × 10–3 M –0.33, 10–7 cm2 s–1, η = 5.9M 0, cm3 g–1. An experimentally high level of molecular compactness is then also reflected by the corresponding contraction factors, which show up to 50 times less molecular volume of HPGs at high molar mass values than their linear analogues.
Organic polymer‐based batteries represent a promising alternative to present‐day metal‐based systems and a valuable step toward printable and customizable energy storage devices. However, most ...scientific work is focussed on the development of new redox‐active organic materials, while straightforward manufacturing and sustainable materials and production will be a necessary key for the transformation to mass market applications. Here, a new synthetic approach for 2,2,6,6‐tetramethyl‐4‐piperinidyl‐N‐oxyl (TEMPO)‐based polymer particles by emulsion polymerization and their electrochemical investigation are reported. The developed emulsion polymerization protocol based on an aqueous reaction medium allowed the sustainable synthesis of a redox‐active electrode material, combined with simple variation of the polymer particle size, which enabled the preparation of nanoparticles from 35 to 138 nm. Their application in cell experiments revealed a significant effect of the size of the active‐polymer particles on the performance of poly(2,2,6,6‐tetramethyl‐4‐piperinidyl‐N‐oxyl methacrylate) (PTMA)‐based electrodes. In particular rate capabilities were found to be reduced with larger diameters. Nevertheless, all cells based on the different particles revealed the ability to recover from temporary capacity loss due to application of very high charge/discharge rates.
Sustainable and efficient organic electrode: A new synthetic approach for polymers for organic batteries includes an emulsion polymerization with adjustable particle sizes in aqueous dispersions and allows the sustainable manufacturing of active materials and composite electrodes. The electrochemical investigation shows that the influence of particle sizes and the resulting morphologies of composite films on the cell performance is as important as the active material itself.
A concise synthesis for the monomer 2-ferrocenylethyl methacrylate is presented. This versatile monomer can be homopolymerized to yield highly lipophilic, stimuli-responsive homopolymers and can also ...be used to further synthesize water-soluble copolymers. For the first time, the X-ray crystal structure of this monomer is shown. The copolymerization with two different ionic monomers was thoroughly investigated at various temperatures. Electrochemical investigations were performed with a well-established viologen to assess the viability of the new material for possible energy storage scenarios. Charge storage experiments at ambient and elevated temperature point toward a satisfying stability of the new materials, with charge recoveries of approximately 95%. The Coulombic efficiency of the materials was determined via galvanostatic cycling and was found to be above 99%, which is comparable to other suitable redox-active polymers for charge storage studies.
To explore the relationship between thermal properties of a polymer and the biological performance of the resulting nanoparticle, all other parameters, including the hydrophobicity, should be kept ...constant. For this purpose, a gradient and a block copolyester were tailor-made via the triazabicyclodecene catalyzed ring-opening copolymerization of δ-valerolactone (δVL) and δ-decalactone (δDL) to match the hydrophobicity of poly(ε-caprolactone) (PεCL). The degree of crystallinity of the semicrystalline materials was significantly reduced due to the incorporation of amorphous PδDL segments, as confirmed by dynamic scanning calorimetry. Atomic force microscopy revealed short and randomly oriented crystals in the gradient copolymer but longer and parallel aligned crystals for the block copolymer and PεCL. The stiffness of nanoparticles (D h ≈ 170 nm) prepared from the polyesters correlated to the bulk crystallinity. The set of nanoparticles with constant hydrophobicity and size will facilitate direct access to the influence of the nanoparticle crystallinity on biological processes such as enzymatic degradation, drug release, and cellular uptake.
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•Poly(ethylene glycol) polymers are stable, mobile, and reactive in porous media.•We investigated the novel tracer in columns filled with quartz, goethite, and illite.•Adsorption of ...polymers to silicate surfaces is governed by Langmuir-type isotherms.•Transport was predicted independently with striking agreement to observation.
A prominent fraction of mobile organic matter in natural aqueous soil solutions is formed by molecules in sizes that seamlessly exceed the lower end of what is defined as a colloid. The hydrodynamics and the functional diversity of these molecules result in a transport behavior that is fundamentally different from smaller compounds. However, there is a lack of “reactive tracers” that allow for the study of colloidal transport phenomena appropriately. We hypothesize that tailor-made and well-defined synthetic polymers can overcome this limitation.
We prepared and characterized the hydrodynamic properties of water-soluble poly(ethylene glycol)s (PEG) and studied their adsorption to mixtures of quartz, illite, and goethite in batch and column experiments.
We used this information to independently predict the transport of PEG with striking agreement to the observed mean breakthrough times in all porous media. As PEG transport can be comprehensively and quantitatively reconstructed, we conclude that functionalized PEGs are promising candidates to be used as tailorable and non-toxic tracers available in the size range of natural organic (macro-)molecules.
In the present work, the polymerization process of ethylene oxide (EO) leading to diphenyl-PEO-OH with a molar mass of 5000 and 10,000 g mol−1 in different ethers used as solvents was investigated. ...The aim was to gain access to the kinetics of the anionic ring-opening polymerization (AROP) of EO by an online and in-situ real-time method and to test alternative “greener” solvents in comparison to the well-established solvents, e.g. tetrahydrofuran (THF). For this purpose, we chose two promising “green” ethers, methyl tetrahydrofuran (MeTHF) and cyclopentyl methyl ether (CPME), with improved properties regarding reduced peroxide formation, higher boiling points, easier drying, and lower water solubility. During the AROP in the custom-built setup, in-situ IR measurements were performed and the final products were characterized by SEC, MALDI-TOF-MS, and 1H NMR measurements, as well as newly in-house developed liquid chromatography (LC) investigations for purity analysis and diol impurity content estimations. Results presented in this study show that the controlled polymerization of EO in the tested alternative solvents represents a viable alternative to commonly established ones, as based on our kinetic studies and product characterization results.
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•Green ethers as solvent alternatives are compared to classical solvent THF for polymerization of ethylene oxide (EO).•In-situ kinetic studies by online FTIR measurements.•Characterization by SEC, MALDI-TOF-MS, and 1H NMR measurements.•LC investigations for purity analysis and diol impurity content estimations.
Shape‐memory polymers (SMPs) are well investigated smart materials. With their ability to memorize their original shape they are interesting candidates for a large range of applications. Certain SMPs ...feature triple shape‐memory behavior. In these cases, it is possible to fix two different temporary shapes. However, the exact quantification of the individual steps regarding their programming and recovery rate is difficult and has not been possible so far. In this work, a novel approach for the analysis and exact quantification of triple SMPs is presented. By applying a customized rheology protocol, it is possible to perform and to analyze torsional and tensional experiments simultaneously. Consequently, different shapes in different directions (vertical and horizontal) can be fixed and the individual steps can be investigated independently at different switching temperatures.
A new method for the quantification of triple‐shape memory behavior of polymers is presented. For this purpose, twisting and elongation are studied separately from each other enabling the investigation of each recovery step without the interference of the other one. Thus, realistic values for the triple‐shape memory behavior are obtained.
In this work, the synthesis and characterization of a compact, ferrocene tetramer and a linear viologen polymer is reported. The latter material is a new, 4,4′‐bipyridine containing, organo‐soluble ...polymer. As aimed for solubility in nonpolar solvents, a 2‐ethylhexyl‐moiety to promote organosolubility and 4‐vinylbenzyl serving as a polymerizable group are introduced to a 4,4′‐bipyridine. The halide anions of the monomer cation are exchanged to bis(trifluoromethansulfon)imide, which further enhances organosolubility. The monomer is subsequently copolymerized with styrene by free radical polymerization. In addition, a four‐ferrocene‐containing compact structure, based on pentaerythritol, is synthesized via the straightforward radical thiol‐ene reaction. The polymer solutions are thoroughly characterized hydrodynamically. Subsequently, propylene carbonate‐based solutions of both materials are prepared to allow an assessment for future energy storage applications. This is done by testing battery characteristics in a custom‐made flow‐cell with a simple dialysis membrane for physical separation of the active materials. The capability of energy storage is verified by leaving the charged materials in solution in an open circuit for 24 h. Here, more than 99% of the stored charges can be recovered. Cycling the battery for 100 times reveals the remarkable stability of the materials of only 0.2% capacity loss per day in the battery setup.
A new, 4,4′‐bipyridine containing, organosoluble monomer is synthesized, its use as a precursor for polymers is investigated, and its solution characteristics studied. A multiple ferrocene moiety‐containing molecularly more compact material is synthesized, enabling a battery with high capacity retention over multiple days of cycling. Solution properties are accessed to study the materials, that is, linear polymers and more compact structures.
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