Kolloid-basierte Polymertemplate zur Herstellung hybrider und anorganischer poröser Architekturen

Ziel dieser Arbeit war die maßgeschneiderte Synthese hybrider und nanokompositärer Kern-Schale Polymerkolloide zur Herstellung poröser Architekturen. Die Grundlage hierfür bietet zum einen die starved-feed Emulsionspolymerisation als bewährte Methode zur Herstellung monodisperser Kern-Schale-Partikel mit gezielt einstellbarer Polymerzusammensetzung und definierten Kern-Schale-Verhältnissen. Zum anderen wurde das Verfahren der Schmelze-Scher-Organisation zur effizienten Herstellung freitragender kolloidal kristalliner Strukturen eingesetzt. Während der Schmelze-Scher-Organisation kommt es, durch Anlegen von Druck und Temperatur, zu einem radialen Fluss der Polymermasse und die Kern-Partikel bilden einen kolloidalen Kristall in einer Matrix des Schalenmaterials. Anschließend konnten durch eine selektive Entfernung des kolloidalen Kristalls als Templat hybride und anorganische poröse Architekturen generiert werden. Im Rahmen dieser Arbeit wurde diese Strategie auf drei unterschiedliche Materialsysteme angewendet. Einerseits wurden selbstvernetzende kolloidal kristalline Filme auf Basis bifunktioneller Alkoxysilane hergestellt, welche anschließend durch eine thermische Behandlung in ein poröses Hybridmaterial überführt werden konnten. Andererseits wurden poröse Kohlenstoffmaterialien ausgehend von polyacrylnitril-haltigen Kern-Schale Partikeln hergestellt. Abschließend konnten poröse Siliciumcarbid Keramiken ausgehend von Allylhydridopolycarbosilanen mittels der eingesetzten Templat-Strategie hergestellt werden

Free-Standing and Self-Crosslinkable Hybrid Films by Core−Shell Particle Design and Processing

The utilization and preparation of functional hybrid films for optical sensing applications and membranes is of utmost importance. In this work, we report the convenient and scalable preparation of self-crosslinking particle-based films derived by directed self-assembly of alkoxysilane-based cross-linkers as part of a core-shell particle architecture. The synthesis of well-designed monodisperse core-shell particles by emulsion polymerization is the basic prerequisite for subsequent particle processing via the melt-shear organization technique. In more detail, the core particles consist of polystyrene (PS) or poly(methyl methacrylate) (PMMA), while the comparably soft particle shell consists of poly(ethyl acrylate) (PEA) and different alkoxysilane-based poly(methacrylate)s. For hybrid film formation and convenient self-cross-linking, different alkyl groups at the siloxane moieties were investigated in detail by solid-state Magic-Angle Spinning Nuclear Magnetic Resonance (MAS, NMR) spectroscopy revealing different crosslinking capabilities, which strongly influence the properties of the core or shell particle films with respect to transparency and iridescent reflection colors. Furthermore, solid-state NMR spectroscopy and investigation of the thermal properties by differential scanning calorimetry (DSC) measurements allow for insights into the cross-linking capabilities prior to and after synthesis, as well as after the thermally and pressure-induced processing steps. Subsequently, free-standing and self-crosslinked particle-based films featuring excellent particle order are obtained by application of the melt-shear organization technique, as shown by microscopy (TEM, SEM)

Kolloid-basierte Polymertemplate zur Herstellung hybrider und anorganischer poröser Architekturen

Ziel dieser Arbeit war die maßgeschneiderte Synthese hybrider und nanokompositärer Kern-Schale Polymerkolloide zur Herstellung poröser Architekturen. Die Grundlage hierfür bietet zum einen die starved-feed Emulsionspolymerisation als bewährte Methode zur Herstellung monodisperser Kern-Schale-Partikel mit gezielt einstellbarer Polymerzusammensetzung und definierten Kern-Schale-Verhältnissen. Zum anderen wurde das Verfahren der Schmelze-Scher-Organisation zur effizienten Herstellung freitragender kolloidal kristalliner Strukturen eingesetzt. Während der Schmelze-Scher-Organisation kommt es, durch Anlegen von Druck und Temperatur, zu einem radialen Fluss der Polymermasse und die Kern-Partikel bilden einen kolloidalen Kristall in einer Matrix des Schalenmaterials. Anschließend konnten durch eine selektive Entfernung des kolloidalen Kristalls als Templat hybride und anorganische poröse Architekturen generiert werden. Im Rahmen dieser Arbeit wurde diese Strategie auf drei unterschiedliche Materialsysteme angewendet. Einerseits wurden selbstvernetzende kolloidal kristalline Filme auf Basis bifunktioneller Alkoxysilane hergestellt, welche anschließend durch eine thermische Behandlung in ein poröses Hybridmaterial überführt werden konnten. Andererseits wurden poröse Kohlenstoffmaterialien ausgehend von polyacrylnitril-haltigen Kern-Schale Partikeln hergestellt. Abschließend konnten poröse Siliciumcarbid Keramiken ausgehend von Allylhydridopolycarbosilanen mittels der eingesetzten Templat-Strategie hergestellt werden

POSS-Containing Polymethacrylates on Cellulose-Based Substrates: Immobilization and Ceramic Formation

The combination of cellulose-based materials and functional polymers is a promising approach for the preparation of porous, biotemplated ceramic materials. Within this study, cellulose substrates were functionalized with a surface-attached initiator followed by polymerization of (3-methacryloxypropyl)heptaisobutyl-T8-silsesquioxane (MAPOSS) by means of surface-initiated atom transfer radical polymerization (ATRP). Successful functionalization was proven by infrared (IR) spectroscopy as well as by contact angle (CA) measurements. Thermal analysis of the polymer-modified cellulose substrates in different atmospheres (nitrogen and air) up to 600 ◦C led to porous carbon materials featuring the pristine fibre-like structure of the cellulose material as shown by scanning electron microscopy (SEM). Interestingly, spherical, silicon-containing domains were present at the surface of the cellulose-templated carbon fibres after further ceramisation at 1600 ◦C, as investigated by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) measurements

Free-Standing and Self-Crosslinkable Hybrid Films by Core–Shell Particle Design and Processing

The utilization and preparation of functional hybrid films for optical sensing applications and membranes is of utmost importance. In this work, we report the convenient and scalable preparation of self-crosslinking particle-based films derived by directed self-assembly of alkoxysilane-based cross-linkers as part of a core-shell particle architecture. The synthesis of well-designed monodisperse core-shell particles by emulsion polymerization is the basic prerequisite for subsequent particle processing via the melt-shear organization technique. In more detail, the core particles consist of polystyrene (PS) or poly(methyl methacrylate) (PMMA), while the comparably soft particle shell consists of poly(ethyl acrylate) (PEA) and different alkoxysilane-based poly(methacrylate)s. For hybrid film formation and convenient self-cross-linking, different alkyl groups at the siloxane moieties were investigated in detail by solid-state Magic-Angle Spinning Nuclear Magnetic Resonance (MAS, NMR) spectroscopy revealing different crosslinking capabilities, which strongly influence the properties of the core or shell particle films with respect to transparency and iridescent reflection colors. Furthermore, solid-state NMR spectroscopy and investigation of the thermal properties by differential scanning calorimetry (DSC) measurements allow for insights into the cross-linking capabilities prior to and after synthesis, as well as after the thermally and pressure-induced processing steps. Subsequently, free-standing and self-crosslinked particle-based films featuring excellent particle order are obtained by application of the melt-shear organization technique, as shown by microscopy (TEM, SEM)

Preceramic core-shell particles for the preparation of hybrid colloidal crystal films by melt-shear organization and conversion into porous ceramics

In this work, the preparation of porous hybrid particle-based films by core-shell particle design and convenient film preparation is reported. Monodisperse core particles consisting of poly(methyl methacrylate‑co‑allyl methacrylate) (P(MMA‑co‑ALMA)) were synthesized by starved-feed emulsion polymerization followed by the introduction of an initiator-containing monomer (inimer) for subsequent atom transfer radical polymerization (ATRP). The inimer shell allowed for the introduction of allylhydrido polycarbosilane (SMP-10) under ATRP conditions by grafting to the core particles. The functionalization of the prepared core-shell particles was investigated by IR spectroscopy (FTIR), scanning transmission electron microscopy (STEM) and solid-state NMR combined with dynamic nuclear polarization (DNP). The obtained hard core/soft preceramic shell particles were subjected to the melt-shear organization technique, enabling a convenient alignment into a colloidal crystal structure in one single step without the presence of a dispersion medium or solvent for the designed particles. Moreover, the hybrid particle-based films were converted into a porous ceramic structure upon thermal treatment. As a result, freestanding ceramic porous films have been obtained after degradation of the organic template core particles. Noteworthy, the conversion of the matrix material consisting of SMP-10 into the ceramic occurred with preservation of the pristine colloidal crystal template structure. Herein, the first example of core-shell particle preparation by combining different polymerization methodologies and application of the convenient melt-shear organization technique is shown, paving a new way to ceramic materials with tailored morphology and porosity

The VAMP‐associated protein VAPB is required for cardiac and neuronal pacemaker channel function

International audienceHyperpolarization-activated cyclic nucleotide-gated (HCN) channels encode neuronal and cardiac pacemaker currents. The composition of pacemaker channel complexes in different tissues is poorly understood, and the presence of additional HCN modulating subunits was speculated. Here we show that vesicle-associated membrane protein-associated protein B (VAPB), previously associated with a familial form of amyotrophic lateral sclerosis 8, is an essential HCN1 and HCN2 modulator. VAPB significantly increases HCN2 currents and surface expression and has a major influence on the dendritic neuronal distribution of HCN2. Severe cardiac bradycardias in VAPB-deficient zebrafish and VAPB-/- mice highlight that VAPB physiologically serves to increase cardiac pacemaker currents. An altered T-wave morphology observed in the ECGs of VAPB-/- mice supports the recently proposed role of HCN channels for ventricular repolarization. The critical function of VAPB in native pacemaker channel complexes will be relevant for our understanding of cardiac arrhythmias and epilepsies, and provides an unexpected link between these diseases and amyotrophic lateral sclerosis.-Silbernagel, N., Walecki, M., Schäfer, M.-K. H., Kessler, M., Zobeiri, M., Rinné, S., Kiper, A. K., Komadowski, M. A., Vowinkel, K. S., Wemhöner, K., Fortmüller, L., Schewe, M., Dolga, A. M., Scekic-Zahirovic, J., Matschke, L. A., Culmsee, C., Baukrowitz, T., Monassier, L., Ullrich, N. D., Dupuis, L., Just, S., Budde, T., Fabritz, L., Decher, N. The VAMP-associated protein VAPB is required for cardiac and neuronal pacemaker channel function