The self‐assembly of polymers is a major topic in current polymer chemistry. In here, the self‐assembly of a pullulan based double hydrophilic block copolymer, namely ...pullulan‐b‐poly(N,N‐dimethylacrylamide)‐co‐poly(diacetone acrylamide) (Pull‐b‐(PDMA‐co‐PDAAM)) is described. The hydrophilic block copolymer induces phase separation at high concentration in aqueous solution. Additionally, the block copolymer displays aggregates at lower concentration, which show a size dependence on concentration. In order to stabilize the aggregates, crosslinking via oxime formation is described, which enables preservation of aggregates at high dilution, in dialysis and in organic solvents. With adequate stability by crosslinking, double hydrophilic block copolymer (DHBC) aggregates open pathways for potential biomedical applications in the future.
The double hydrophilic block copolymer poly(N,N‐dimethylacrylamide)‐b‐pullulan shows an unique aggregation behavior in aqueous solution at concentrations above 20 wt% leading to a polymer rich and a polymer depleted phase. At this concentration crosslinking is performed to synthesize hydrophilic particles in the size range of 30 nm to 1 µm that are stable at low concentration and in organic solvent.
Polysaccharides have attracted considerable attention in a broad range of applications in recent years, which is due to their remarkable features such as biocompatibility, biodegradability, renewable ...origin, and facile modification. Considerable research efforts have been focused on developing polysaccharide nanoparticles and to promote their applications in various areas and biomedicine in particular. The present review highlights the properties of common polysaccharides used in nanoparticle formation as well as strategies to fabricate polysaccharide nanoparticles. Furthermore, the combination of polysaccharide nanoparticles and polymers is presented and brought into the context of applications. Finally, applications of polysaccharide nanoparticles as nano-delivery system, Pickering emulsion stabilisers, and material reinforcing agent in the fields of nanomedicine, cosmetics, and food system are highlighted. Moreover, this review describes and critically discusses present limitations and drawbacks in the preparation and use of polysaccharide nanoparticles, revealing directions to develop polysaccharide nanoparticles for further utilisation in various applications in the future.
Aqueous multi-phase systems have attracted a broad interest in recent years, which is mainly due to their applicability in biology for purification and isolation of biomolecules and also for ...separation of particles as well as environment for enzymatic reactions. Here, three polyacrylamides poly(N,N-dimethylacrylamide), poly(acrylamide), and poly(4-acryloylmorpholine) with ultra-high molar mass were synthesized via photo-induced reversible addition–fragmentation chain-transfer polymerization (M n > 700,000 g·mol–1). The polymers were combined to form aqueous multi-phase systems with low total polymer concentration as low as 1.1 to 2.1 wt %. Furthermore, the aqueous multi-phase system could be transformed into water-in-water (w/w) emulsions, stabilized by layered double hydroxide nanoparticles. Due to the low polymer content, these aqueous multi-phase systems open up new pathways, for example, in the separation of biomolecules or the compartmentalization of aqueous environments in catalysis.
Macromolecular crowding plays a critical role in the kinetics of enzymatic reactions. Dynamic compartmentalization of biological components in living cells due to liquid–liquid phase separation ...represents an important cell regulatory mechanism that can increase enzyme concentration locally and influence the diffusion of substrates. In the present study, we probed partitioning of two enzymes (horseradish-peroxidase and urate-oxidase) in a poly(ethylene glycol)–dextran aqueous two-phase system (ATPS) as a function of salt concentration and ion position in the Hofmeister series. Moreover, we investigated enzymatic cascade reactions and their kinetics within the ATPS, which revealed a strong influence of the ion hydration stemming from the background electrolyte on the partitioning coefficients of proteins following the Hofmeister series. As a result, we were able to realize cross-partitioning of two enzymes because of different protein net charges at a chosen pH. Our study reveals a strong dependency of the enzyme activity on the substrate type and crowding agent interaction on the final kinetics of enzymatic reactions in the ATPS and therefore provides substantial implications en route toward dynamic regulation of reactivity in synthetic protocells.
Experimental evidence is presented showing that the direct formation of anisotropic colloidal polymer particles via aqueous heterophase polymerization is essentially controlled by the entropy gain of ...the linear fraction in the semi-interpenetrating network of the seed particles during swelling. Anisotropic particles are produced via photoinitiated polymerization, allowing swelling and polymerization to take place at the same temperature. These experiments prove that the temperature effect on rubber elasticity is, if at all, only of minor importance for the formation of anisotropic polymer particles. The major significance of swelling of the seed particles for the whole process is underlined by additional studies with optical microscopy and model simulations.
The self‐assembly of block copolymers constitutes a timely research area in polymer science with implications for applications like sensing or drug‐delivery. Here, the unprecedented aggregation ...behavior of high molar mass block copolymer poly(N,N‐diethylacrylamide)‐b‐poly(4‐acryloylmorpholine) (PDEA‐b‐PAM) (Mn>400 kg mol−1) in organic solvent tetrahydrofuran (THF) is investigated. To elucidate the aggregation, dynamic light scattering, cryo‐transmission electron microscopy, and turbidimetry are employed. The aggregate formation is assigned to the unprecedented upper critical solution temperature behavior of PAM in THF at elevated concentrations (> 6 wt.%) and high molar masses. Various future directions for this new thermo‐responsive block copolymer are envisioned, for example, in the areas of photonics or templating of inorganic structures.
Aggregation behavior of high molar mass block copolymer poly(N,N‐diethylacrylamide)‐b‐poly(4‐acryloylmorpholine) in organic solvent tetrahydrofuran is investigated.
Front Cover: In article number 2000053 by Rumiana Dimova, Bernhard V. K. J. Schmidt, and co‐workers, the double hydrophilic block copolymer poly(N,N‐dimethylacrylamide)‐b‐pullulan shows a unique ...aggregation behavior in aqueous solution at concentrations above 20 wt% leading to a polymer rich and a polymer depleted phase. At this concentration crosslinking is performed to synthesize hydrophilic particles in the size range of 30 nm to 1 µm that are stable at low concentration and in organic solvent.
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