Throughout the last decades, magnetic nanoparticles (MNP) have gained tremendous interest in different fields of applications like biomedicine (e.g., magnetic resonance imaging (MRI), drug delivery, hyperthermia), but also more technical applications (e.g., catalysis, waste water treatment) have been pursued. Different surfactants and polymers are extensively used for surface coating of MNP to passivate the surface and avoid or decrease agglomeration, decrease or modulate biomolecule absorption, and in most cases increase dispersion stability. For this purpose, electrostatic or steric repulsion can be exploited and, in that regard, surface charge is the most important (hybrid) particle property. Therefore, polyelectrolytes are of great interest for nanoparticle coating, as they are able to stabilize the particles in dispersion by electrostatic repulsion due to their high charge densities. In this review article, we focus on polyzwitterions as a subclass of polyelectrolytes and their use as coating materials for MNP. In the context of biomedical applications, polyzwitterions are widely used as they exhibit antifouling properties and thus can lead to minimized protein adsorption and also long circulation times.

We herein report the synthesis and characterization of dual stimuli-responsive poly­(2-iso-propyl-2-oxazoline)-block-poly­(2-acrylamido glycolic acid) (PiPrOx-b-PAGA) double hydrophilic block copolymers (BCPs) by an effective combination of ring-opening and reversible addition–fragmentation chain transfer (RAFT) polymerization. The resulting materials are responsive toward several external triggers: (1) the PiPrOx segment undergoes a coil-to-globule transition upon heating above the cloud point temperature (T CP), (2) the PAGA block chelates M2+ metal ions and provides straightforward access to nanostructured hybrid materials, and (3) prolonged heating above the T CP for PiPrOx enables crystallization-driven solution self-assembly (CDSA) toward anisotropic micelles and superstructures. We are further able to show that the cloud point temperature (T CP) of PiPrOx-b-PAGA micelles can be tuned from ∼30 to 68 °C by varying either the BCP composition (PiPrOx to PAGA ratio) or by the amount of metal ions being present. The different aggregates were characterized by transmission electron microscopy (TEM), wide-angle X-ray scattering (WAXS), and dynamic light scattering (DLS). Our results indicate that micellar size, shape, and T CP are closely connected to BCP composition and the nature of chelated metal ions. In our opinion, such inorganic–organic hybrid materials are of interest with regard to (photo)­catalysis, as sensors, or as potential drug delivery systems.

The reversible electrostatic adsorption of the cationic dye methylene blue (MB) as a model compound to polydehydroalanine (PDha)-coated magnetic multicore nanoparticles (MCNP) is presented. The pH responsiveness of the zwitterionic coating material enables reversible switching of the net surface charge of the PDha@MCNP hybrid particles by changes in pH and thus allows reversible adsorption of MB at neutral pH and desorption at low pH values. The resulting hybrid materials can be very interesting systems in the context of water purification, and the reversible adsorption is studied using UV-vis spectroscopy under varying surrounding conditions. The particles are characterized using dynamic light scattering, zeta potential measurements, transmission electron microscopy, and thermogravimetric analysis.

Compared to other commonly used materials in the field of soft actuators, cellulose offers many advantages such as low cost, sustainability, versatile applications, and abundancy. Due to the enormous and growing demand in the functional flexible electronics industry, cellulose‐based soft actuators are receiving a lot of attention and are undergoing an exciting development. In this focused review, the milestones and recent achievements of cellulose‐based actuators are presented. The actuation energy of the actuators is mainly generated through external stimuli like electricity, temperature, magnetic fields, light, or moisture. Different systems which use these stimuli and corresponding fabrication techniques for these materials, such as self‐assembly and layer by layer deposition are discussed. Further, the currently applied strategies to achieve programmable actions in soft actuators will be reviewed, which allow control over responding deformation. Finally, the pending challenges and some potential solutions in the upcoming development of cellulose‐based actuators are summarized.

The low thermal conductivity of amorphous polymers typically prevents their usage in thermal management applications. Therefore, increasing their intrinsic thermal conductivity poses an exciting scientific challenge. One approach is to promote attractive interchain interactions. Here, we investigate the thermal conductivity of several ampholytic polymers. This unique class of polymers offers H-bond donor and acceptor groups in each repeat unit and constitutes an onecomponent system. We use IR spectroscopy to characterize the bonding strength and motifs based on the carbonyl peak. For the dry ampholytic polymers, we find a correlation between H-bond strength and thermal conductivity. We also characterized the influence of hydration at various relative humidity conditions, which mostly led to an increase in thermal conductivity. This increase can be rationalized by the formation of a water-polymer nanocomposite material and can be described by volume-weighted mixing models. conductivity. This is an ongoing challenge to be addressed by polymer chemists and engineers over the next years. ASSOCIATED CONTENT Supporting Informationthermal conductivity measurements, IR spectroscopy of individual polymers, DSC measurements, effective medium mixing models, and microscopy of the transducer layer