Synthesis and Selective Loading of Polyhydroxyethyl Methacrylate‑<i>l</i>‑Polysulfone Amphiphilic Polymer Conetworks

Polyhydroxyethyl methacrylate-<i>linked by</i>-polysulfone amphiphilic polymer conetworks of two types of segments with <i>T</i>_g above room temperature are presented. The conetworks are prepared by free radical copolymerization of methacryloyl-terminated PSU macromers with 2-ethyl methacrylate, followed by removal of the TMS protecting groups by acidic hydrolysis. Phase separation in the nanometer range due to the immiscibility of the two covalently linked segments is observed using transmission electron and scanning force microscopy. The swelling of the conetworks in water and methanol as polar solvents and chloroform as nonpolar solvent are studied gravimetrically and then in a more detailed fashion by solid-state NMR spectroscopy. Selective swelling and also targeted loading of a small organic model compound specifically to one of the two phases are demonstrated

Synergistic Growth of Giant Wormlike Micelles in Ternary Mixed Surfactant Solutions: Effect of Octanoic Acid

The synergistic growth of giant wormlike micelles in ternary mixed solutions composed of an anionic surfactant (sodium laurylethersulfate, SLES), a zwitterionic surfactant (cocamidopropyl betaine, CAPB), and octanoic acid (HC8) is studied. Rheological data and their analysis in terms of Cole–Cole plots and micellar characteristic times are presented, and the micellar structures behind the observed rheological behavior are revealed by cryo-TEM micrographs. The surfactant composition is fixed near the maximal micelle size of the binary SLES + CAPB system, whereas the concentration of HC8 is varied. At a given HC8 concentration, the viscosity of the ternary micellar solutions exhibits a very high and sharp peak. Polarized-light optical microscopy indicates that all investigated solutions are isotropic rather than liquid-crystalline. The cryo-TEM imaging shows complex phase behavior: wormlike micelles to the left of the peak, giant entangled wormlike micelles at the peak, and long wormlike micelles coexisting with multiconnected micellar aggregates to the right of the peak. The formation of multiconnected micelles leads to a drop in viscosity at the higher concentrations. The results contribute to a better understanding of the structure–rheology relations in micellar surfactant solutions and could be useful for controlling the properties of formulations in personal-care and house-hold detergency

Modulation of Domain Size in Polycrystalline n‑Type Dicyanoperylene Mono- and Bilayer Transistors

A single molecular layer (monolayer) of organic semiconductors is proven to be sufficient to create a conducting channel for charge carriers in field-effect transistors, which is an ideal platform to investigate the correlation between molecular self-assembly and device performance. Herein, ultrathin films including mono- and bilayers of an n-type dicyanoperylene (PDI₈-CN₂) are solution-processed by dip-coating. The domain size of the polycrystalline layers is modulated <i>via</i> the surface roughness of the dielectric within an extremely narrow window from 0.15 to 0.39 nm. When the surface roughness is varied from smooth to rough, the domain size and molecular order in the monolayer are significantly decreased, leading to the reduction in electron mobility by 3 orders of magnitude. On the contrary, a lower roughness dependence is observed in the case of the bilayers, with only a slight difference in domain size and charge carrier transport. On the smooth surface, the bilayers exhibit a transistor performance identical to that of the bulk film, confirming that the first few layers near the dielectric dominate the charge carrier transport. Additionally, these results provide insights into the intrinsic role of the interfacial microstructure of small molecular organic semiconductors

Enlarging the Toolbox: Epoxide Termination of Polyferrocenylsilane (PFS) as a Key Step for the Synthesis of Amphiphilic PFS–Polyether Block Copolymers

Epoxide termination and functionalization of living poly­(ferrocenyldimethylsilane) (PFDMS) is introduced by precapping the living PFDMS with a 4/2 molar mixture of 1,1-diphenylethylene and 1,1-dimethylsilacyclobutane acting as a “carbanion pump” system. Subsequent addition of allyl glycidyl ether (AGE) leads to quantitatively functionalized PFDMS–AGE polymers with molecular weights between 1500 and 15 400 g mol^–1 and polydispersity indices ≤1.10, carrying one hydroxyl group and an additional allylic double bond. PFDMS–AGE was then applied as a macroinitiator for the living anionic ring-opening polymerization of ethylene oxide (EO) to generate amphiphilic and water-soluble poly­(ferrocenyldimethylsilane-<i>b</i>-ethylene oxide) block copolymers with a low polydispersity index. All polymers have been characterized by ¹H NMR spectroscopy, DOSY ¹H NMR spectroscopy, size exclusion chromatography (SEC), and MALDI-ToF mass spectrometry. In addition, for the characterization of the morphology of the PFDMS-<i>b</i>-PEO block copolymers transmission electron microscopy (TEM) was performed in methanol, confirming the formation of cylindrical micelles with an organometallic core and polyether corona

Toward Artificial Mitochondrion: Mimicking Oxidative Phosphorylation in Polymer and Hybrid Membranes

For energy supply to biomimetic constructs, a complex chemical energy-driven ATP-generating artificial system was built. The system was assembled with bottom-up detergent-mediated reconstitution of an ATP synthase and a terminal oxidase into two types of novel nanocontainers, built from either graft copolymer membranes or from hybrid graft copolymer/lipid membranes. The versatility and biocompatibility of the proposed nanocontainers was demonstrated through convenient system assembly and through high retained activity of both membrane-embedded enzymes. In the future, the nanocontainers might be used as a platform for the functional reconstitution of other complex membrane proteins and could considerably expedite the design of nanoreactors, biosensors, and artificial organelles

Crystallinity Tunes Permeability of Polymer Nanocapsules

Permeability is the key property of nanocapsules because it dictates the release rate of encapsulated payloads. Herein, we engineer the crystallinity of polymers confined in the shell of nanocapsules. Nanocapsules with crystalline shells are formed from polyurea and polyphosphoester. The thermal properties, such as crystallization temperature and degree of crystallinity, are different from the bulk. The degree of crystallinity is used to control the shell permeability and, therefore, the release of encapsulated payloads, such as fluorescent dyes, typically used as model components for biomedical applications

Incorporation of Nanoparticles into Polymersomes: Size and Concentration Effects

Because of the rapidly growing field of nanoparticles in therapeutic applications, understanding and controlling the interaction between nanoparticles and membranes is of great importance. While a membrane is exposed to nanoparticles its behavior is mediated by both their biological and physical properties. Constant interplay of these biological and physicochemical factors makes selective studies of nanoparticles uptake demanding. Artificial model membranes can serve as a platform to investigate physical parameters of the process in the absence of any biofunctional molecules and/or supplementary energy. Here we report on photon- and fluorescence-correlation spectroscopic studies of the uptake of nanosized SiO₂ nanoparticles by poly(dimethylsiloxane)-<i>block</i>-poly(2-methyloxazoline) vesicles allowing species selectivity. Analogous to the cell membrane, polymeric membrane incorporates particles using membrane fission and particles wrapping as suggested by cryo-TEM imaging. It is revealed that the incorporation process can be controlled to a significant extent by changing nanoparticles size and concentration. Conditions for nanoparticle uptake and controlled filling of polymersomes are presented

Structure Formation in Metal Complex/Polymer Hybrid Nanomaterials Prepared by Miniemulsion

Polymer/complex hybrid nanostructures were prepared using a variety of hydrophobic metal β-diketonato complexes. The mechanism of structure formation was investigated by electron paramagnetic resonance (EPR) spectroscopy and small-angle X-ray scattering (SAXS) in the liquid phase. Structure formation is attributed to an interaction between free coordination sites of metal β-diketonato complexes and coordinating anionic surfactants. Lamellar structures are already present in the miniemulsion. By subsequent polymerization the lamellae can be embedded in a great variety of different polymeric matrices. The morphology of the lamellar structures, as elucidated by transmission electron microscopy (TEM), can be controlled by the choice of anionic surfactant. Using sodium alkylsulfates and sodium dodecylphosphate, “nano-onions” are formed, while sodium carboxylates lead to “kebab-like” structures. The composition of the hybrid nanostructures can be described as bilayer lamellae, embedded in a polymeric matrix. The metal complexes are separated by surfactant molecules which are arranged tail-to-tail; by increasing the carbon chain length of the surfactant the layer distance of the structured nanomaterial can be adjusted between 2 and 5 nm

Effect of Morphological Changes on Presence of Trap States in P3HT:PCBM Solar Cells Studied by Cross-Sectional Energy Filtered TEM and Thermally Stimulated Current Measurements

A combination of energy filtered transmission electron microscopy (EFTEM) and thermally stimulated current (TSC) was used in order to investigate the effect of thermal annealing on the performance of an organic solar cell based on P3HT and PCBM as a well-studied reference system. By probing specific elements, EFTEM allowed spectroscopic imaging with enhanced resolution compared to standard TEM techniques. Here, we applied EFTEM to cross-sections of pristine and thermally annealed organic solar cells to probe the sulfur concentration as a measure for the P3HT distribution within the photoactive layer. Thermal annealing for 10 min at 130 °C resulted in a reordering of P3HT and PCBM into better defined domains. The effect of the morphological changes on the presence of trap states was studied by TSC measurements. The TSC spectra recorded for the pristine and the thermally annealed solar cells showed three contributions, respectively, that could be assigned to the neat materials P3HT and PCBM as well as the blend. The pristine solar cell revealed a significantly lower density of trap states in the P3HT phase compared to the annealed solar cell. In combination with our EFTEM measurements, we were able to attribute this finding to the increased number of P3HT rich domains present in the annealed device. Annealing of P3HT:PCBM solar cells had a beneficial impact not only on the local molecular order, but in particular on providing percolation paths for both charge carrier types