Swelling Behavior and Complex Formation Ability of Ternary Amphoteric Gels based on Allylamine Derivatives and Maleic Acid

Summary: The swelling behavior of an amphoteric gel composed of 50 mol‐% of maleic acid (MA), 25 mol‐% of N,N′‐dimethyldiallylammonium chloride (DMDAAC) and 25 mol‐% of diallylamine (DAA) was studied in aqueous and aqueous‐salt solutions. The isoelectric point (IEP) of the MA‐DMDAAC‐DAA gel determined from swelling experiments was about pH 4.6. Considerable gel swelling with increasing ionic strength was observed at the IEP. Dynamic swelling properties of the amphoteric gel in water with and without added salt were measured at various pH values including the IEP. The swelling behavior of the amphoteric gel was found to depend on the ionization state of the functional groups. It can be described by either a relaxation‐controlled or non‐Fickian (anomalous) mechanism. Swelling‐deswelling properties of the amphoteric gel were also studied in mixtures of water and organic solvents. The amphoteric gel was able to complex sodium poly(styrene sulfonate), sodium lauryl sulfate, the cationic drug richlocain, and the bivalent transition metal ions Cu²⁺, Ni²⁺, Co²⁺, and Zn²⁺. The sorption of polyelectrolyte, surfactant, drug, and metal ions by the amphoteric gel is accompanied by the contraction of the gel network. Partial release of the cationic drug molecules entrapped into the gel volume takes place at the IEP of the amphoteric gel with low activation energy, while neither the anionic polyelectrolyte nor the surfactants are released from the gel interior at the IEP. The swelling‐shrinking behavior of gel‐polyelectrolyte and gel‐surfactant complexes in dependence of pH and ionic strength of the outer solution is similar.

     

Improved Maxwell Model Approach and its Applicability toward Lifetime Prediction of Biobased Viscoelastic Fibers

The evaluation of relaxation measurements is a well-established technique for predicting the lifetime of polymer materials, with research primarily focusing on increasing prediction accuracy and minimizing material testing time. The current study presents a novel approach toward describing the long-term behavior of viscoelastic polymers based on the Maxwell model. It assumes a mean relaxation time of the polymer chains in conjunction with a dimensionless number that accounts for averaged polymer chain inhomogeneities. This coefficient is analogous to the dimensionless number, which successfully describes the asymmetry of both the Weibull distribution and of particle size distribution according to the Rosin, Rammler, Sperling and Bennet model. In comparison to earlier models based on time-superposition principles, the current approach enables lifetime prediction using a single short-term measurement, which must be taken at a properly chosen applied strain. The applicability of the new model in predicting the long-term behavior has been demonstrated by the analysis of the relaxation behavior of semi-crystalline bio-based fibers.     

Design strategies for materials showing thermally activated delayed fluorescence and beyond: Towards the fourth‐generation OLED mechanism

Design strategies for molecules showing thermally activated delayed fluorescence (TADF) are discussed, and a new emitter concept based on an almost “zero‐energy‐gap” is developed. Thermal activation is not substantial. Applied in an organic light emitting diode, all singlet and triplet excitons are harvested directly in the lowest singlet state without time‐delaying TADF. This landmarking mechanism, being beyond TADF, leads to emission decay times in the sub‐μs range.     

Nanoscaling of microdomain spacings in thin films of cylinder-forming block copolymers

We present first quantitative measurements of the characteristic lateral dimensions in thin films of cylinder-forming block copolymers. Using a metrological scanning force microscope and tailor-made image analysis, we map out lateral distances with subnanometer accuracy. Microdomain spacings change in a systematic way as a function of the film thickness and as a function the lateral cylinder bending. We show that in very thin films the unit cell is stretched perpendicular to the plane of the film resulting in lateral distances smaller than those in bulk. The changes are distinct, although small, and can be rationalized within the framework of the strong segregation theory of block copolymers.     

An adenoviral platform for selective self-assembly and targeted delivery of nanoparticles

Metallic nanoparticles (NPs) can be used for the diagnosis, imaging, and therapy of tumors and cardiovascular disease. However, targeted delivery of NPs to specific cells remains a major limitation for clinical realization of these potential treatment options. Herein, a novel strategy for the specific coupling of NPs to a targeted adenoviral (Ad) platform to deliver NPs to specific cells is defined. Genetic manipulation of the gene-therapy vector is combined with a specific chemical coupling strategy. In particular, a high-affinity interaction between a sequence of six-histidine amino acid residues genetically incorporated into Ad capsid proteins and nickel(II) nitrilotriacetic acid on the surface of gold NPs is employed. The selective self-assembly of gold NPs and Ad vectors into multifunctional platforms does not negatively affect the targeting of Ad to specific cells. This opens the possibility of using Ad vectors for targeted NP delivery, thereby providing a new type of combinatorial approach for the treatment of diseases that involves both nanotechnology and gene therapy.     

Simple and rapid synthesis of α-Fe2O3 nanowires under ambient conditions

We propose a simple method for the efficient and rapid synthesis of one-dimensional hematite (α-Fe₂O₃) nanostructures based on electrical resistive heating of iron wire under ambient conditions. Typically, 1–5 μm long α-Fe₂O₃ nanowires were synthesized on a time scale of seconds at temperatures of around 700 ° ⊂. The morphology, structure, and mechanism of formation of the nanowires were studied by scanning and transmission electron microscopies, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman techniques. A nanowire growth mechanism based on diffusion of iron ions to the surface through grain boundaries and to the growing wire tip through stacking fault defects and due to surface diffusion is proposed. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.