Poly(ethylene glycol)s (PEG) are widely and intensely used in the pharmaceutical industry and biomedical applications, and due to this fact, antibodies have recently been reported. Poly(2oxazoline)s (POx) are promising candidates for potential replacement of PEG in related applications, and as such, their hydrodynamic properties and characteristics derived from light scattering experiments are important to reconcile their behavior in solution. In this study, we have investigated the molecular hydrodynamic characteristics of poly(2-methyl-2-oxazoline)s and poly(2-ethyl-2-oxazoline)s in the pharmaceutical molar mass range as base candidates for such applications, prepared by cationic ring-opening polymerization in a microwave reactor. A combined viscometry and sedimentation−diffusion analysis by using sedimentation velocity experiments in an analytical ultracentrifuge includes (i) the study of intrinsic viscosities, (ii) sedimentation coefficients, and (iii) derived translational diffusion coefficients. These characteristics are then interrelated through hydrodynamic invariants that showed consistency between all these hydrodynamic parameters and, consequently, adequate values of derived absolute molar masses. The established scaling relationships of POx could as well be related quantitatively to that of pharmaceutical PEG from a recent study. Complementary, the molar masses were estimated by asymmetrical flow field-flow fractionation (AF4) and size exclusion chromatography (SEC) in conjunction with multiangle laser light scattering (MALLS). Thus, the obtained results of molar masses show an overarching good correlation to that of the hydrodynamic analysis utilizing the ultracentrifuge and viscometry. However, we demonstrate as well that AF4-/SEC-MALLS experiments of macromolecules below 10 000 g mol −1 may provide erroneous information on their molar mass, identified and discussed by the hydrodynamic invariant concept interrelating three independent experimental approaches on the same sample, i.e., (i) intrinsic viscosities, (ii) intrinsic sedimentation coefficients, and (iii) molar masses from light scattering. Our results open the gate for the replacement of pharmaceutical PEG by POx on a physicochemical basis with key first-principles hydrodynamic parameters of interest, all associated with values of the molar mass.

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Herein, we present a novel copolymer (1), which incorporates (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as a redox-active compound and the zwitterionic [(2-(methacryloxy)ethyl)dimethyl-(3-sulfopropyl)]ammonium hydroxide as a solubilizing comonomer, for the application as catholyte species within aqueous redox flow batteries (RFBs). The presented polymer-based redox-active material exhibits a high degree of oxidation and, compared to other commonly utilized active polymeric materials, a high solubility exceeding 20 Ah L −1 , while still featuring a low viscosity in 1.5 M NaCl aq solution. The electrochemical behavior was investigated by cyclic voltammetry, and a reversible redox reaction at E 0 = 0.7 V versus the Ag/AgCl reference electrode of the TEMPO/TEMPO + redox pair was observed. Symmetric design battery studies with two different types of membranes, a size-exclusion versus an anion-exchange membrane, were used to evaluate the applicability of this polymer in the RFB setup. Long-term stability tests over 1000 cycles indicate good stability with a capacity loss of ca. 0.08% per cycle utilizing a size-exclusion and an anion-exchange membrane, respectively. Finally, an allorganic aqueous RFB was operated utilizing 1 as the catholyte species and N,N′-dimethyl-4,4′-bipyridinium dichloride (MV) as the anolyte species. Such RFB exhibits Coulombic efficiencies of 99.01 ± 1.40% over 125 consecutive cycles, an energy efficiency of ca. 93%, and an initial energy density of 5.33 Wh L −1 during the studied discharge process.

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Polymer conjugated biologics form a multibillion dollar market, dominated by poly(ethylene glycol) (PEG). Recent reports linked PEGs to immunological concerns, fueling the need for alternative polymers. Therefore, we are presenting a strategy replacing PEG by poly(2-oxazoline) (POx) polymers using genetically engineered interleukin-4 (IL-4) featuring an unnatural amino acid for site-specific conjugation through bioorthogonal copper-catalyzed azide alkyne cycloaddition (CuAAC). Conjugation yields of IL-4-PEG were poor and did not respond to an increase in the copper catalyst. In contrast, POxylated IL-4 conjugates resulted in homogeneous conjugate outcome, as demonstrated electrophoretically by size exclusion chromatography and analytical ultracentrifugation. Furthermore, POxylation did not impair thermal and chemical stability, and preserved wild-type IL-4 activity for the conjugates as demonstrated by TF-1 cell proliferation and STAT-6 phosphorylation in HEK293T cells, respectively. In conclusion, POxylation provides an interesting alternative to PEGylation with superior outcome for the synthesis yield by CuAAC and resulting in conjugates with excellent thermal and chemical stress profiles as well as biological performances.

The interrelation of experimental rotational and translational hydrodynamic friction data as a basis for the study of macromolecules in solution represents a useful attempt for the verification of hydrodynamic information. Such interrelation originates from the basic development of colloid and macromolecular science and has proven to be a powerful tool for the study of naturally- and synthetically-based, i.e., artificial, macromolecules. In this tutorial review, we introduce this very basic concept with a brief historical background, the governing physical principles, and guidelines for anyone making use of it. This is because very often data to determine such an interrelation are available and it only takes a set of simple equations for it to be established. We exemplify this with data collected over recent years, focused primarily on water-based macromolecular systems and with relevance for pharmaceutical applications. We conclude with future incentives and opportunities for verifying an advanced design and tailored properties of natural/synthetic macromolecular materials in a dispersed or dissolved manner, i.e., in solution. Particular importance for the here outlined concept emanates from the situation that the classical scaling relationships of Kuhn–Mark–Houwink–Sakurada, most frequently applied in macromolecular science, are fulfilled, once the hydrodynamic invariant and/or sedimentation parameter are established. However, the hydrodynamic invariant and sedimentation parameter concept do not require a series of molar masses for their establishment and can help in the verification of a sound estimation of molar mass values of macromolecules.

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