Borane catalysis has emerged as a powerful technology in epoxide polymerization. Still, the structure-activity correlations for these catalysts are not fully understood to date, especially regarding compounds with nonionic backbones. Thus, in this work, 13 different borane catalysts of this respective type are described and investigated for their epoxide oligomerization and polymerization performance, using propylene oxide (PO), 1-butylene oxide (BO) and allyl glycidyl ether (AGE) as monomers. Structurally, special emphasis is put on catalysts with different linker lengths and linker flexibilities as well as the introduction of more than two borane functionalities. Importantly, this screening is conducted both under typical polymerization conditions as well as under the chain transfer agent (CTA)-rich conditions relevant for large-scale production. It is found that suitable preorganization of the borane groups, such as present in biphenyl derivatives, offers a simple route to high-performing catalysts and quantitative monomer conversion of the investigated epoxides. Furthermore, it is demonstrated that a diborane-catalyzed oligomerization can be kept active over weeks, whereby repeated addition of monomer batches (14 steps) constantly results in full conversion and well-defined oligoethers, underlining the practical potential of this method. The absence of co-initiating counter ions is suggested as an inherent advantage of nonionic catalysts.

Modified biomaterials have for years been the focus of research into establishing new bone substitutes. In our preceding in vitro study employing different cell cultures, we developed chemically and mechanically characterized hydrogels based on photocrosslinkable dextran derivatives and demonstrated their cytocompatibility and their beneficial effects on the proliferation of osteoblasts and endothelial cells. In the present in vivo study, we investigate photocrosslinked dextran-based hydrogels in critical size defects in mice to evaluate their potential as carrier systems for cells or for a specific angiogenesis enhancing cytokine to induce bone formation. We could demonstrate that, with optimized laboratory practice, the endotoxin content of hydrogels could be reduced below the Food and Drug Administration (FDA)-limit. Dextran-based hydrogels were either loaded with a monoculture of endothelial cells or a co-culture of human osteoblasts with endothelial cells, or with stromal-derived-growth factor (SDF-1). Scaffolds were implanted into a calvarial defect of critical size in mice and their impact on bone formation was assessed by µCt-analyses, histology and immunohistology. Our study demonstrates that promotion of angiogenesis either by SDF-1 or a monoculture of endothelial cells induces bone regeneration at a physiological level. These in vivo results indicate the potential of dextran-based hydrogel composites in bone regeneration to deliver cells and cytokines to the defect site.

Silicatein, a hydrolytic protein encountered in marine sponges, was immobilized on maghemite (γ-Fe2O3) nanoparticles that were surface functionalized with a reactive mulfunctional polymer. This polymer carries an anchor group based on dopamine which is capable of binding to the γ-Fe2O3 surface and a reactive functional group which allows binding of various biomolecules onto inorganic nanoparticles. This functional nitrilotriacetic acid (NTA) group allows immobilization of His-tagged silicatein on the surface of the γ-Fe2O3 nanoparticles. The surface-bound protein retains its native hydrolytic activity to catalyze formation of silica through copolymerization of alkoxysilanes Si(OR)4. Functionalization of the magnetic nanoparticles and the architecture of the SiO2-coated γ-Fe2O3 nanoparticles was confirmed by TEM studies as well as by FT-IR and optical microscopy.

Magnetic medicines: The immobilization of the abnormal nucleic acid polyinosinic–polycytidylic acid (poly(IC)) on γ-Fe2O3 maghemite nanoparticles through the phosphoramidate route by using a multifunctional polymer is reported. This approach may open new possibilities for magnetic drug delivery applications. The image shows γ-Fe2O3 nanoparticles after polymer functionalization.

Particles on the tube: Here, novel surface functionalization of WS2 nanotubes with polymeric ligands, by complexation with a combination of Ni2+ through a scorpionate-type nitrilotriacetic acid, and immobilization of TiO2 nanoparticles onto the surface of nanotubes is demonstrated (see schematic representation). The synthesis of the functional polymeric ligands was achieved through a reactive polymer precursor route.

The synthesis of MS 2 (M = Mo, W) onion-like nanoparticles by means of a high temperature MOCVD process starting from W(CO)6 and elemental sulfur is reported. The reaction can also be carried out in two steps where the intermediate amorphous WS 2 nanoparticles formed through the high temperature reaction of tungsten and sulfur in the initial phase of the reaction are isolated and converted in a separate annealing step to onion-type WS2 nanoparticles. Based on a study of the temperature dependence of the reaction a set of conditions could be derived where onion-like structures were formed in a one-step reaction. Onion-like structures obtained in the single-step process were filled, whereas the particles obtained by the two-step procedure were systematically hollow. A model could be devised to rationalize the different outcome of the reactions. The MOCVD approach therefore allows a selective synthesis of open and filled fullerene-like chalcogenide nanoparticles. Furthermore, we demonstrate the novel surface functionalization of WS2 nanotubes with polymeric ligands by complexation with a combination of Ni 2+ via an scorpionate-type nitrilotriacetic acid (NTA) and immobilization of TiO 2 nanoparticles onto the surface of nanotubes. Synthesis of such a functional polymeric ligand was achieved via a reactive polymer precursor route.

Bedeckte Wände: Die Koordinationschemie mehrzähniger Liganden ermöglichte die Funktionalisierung der Oberfläche hochgradig inerter MoS2-Nanopartikel. Dabei wurde der vierzähnige Nitrilotriessigsäure-Ligand entweder an einen fluoreszierenden Liganden gekuppelt (zur Detektion) oder an ein reaktives Polymer, das ihn mit den Sulfid- und Oxidoberflächen anorganischer Fulleren-MoS2- bzw. -TiO2-Nanostäbchen verknüpft (siehe Bild).

Drei in einem: TiO2-Nanopartikel wurden mit reaktiven polymeren Liganden funktionalisiert, die drei Arten von Gruppen enthalten: chelatisierende Dopamin-Ankergruppen, eine Bindungsstelle für funktionale Moleküle wie Fluoreszenzfarbstoffe (siehe Bild) sowie Gruppen, die es ermöglichen, die Löslichkeit der anorganischen Nanokristalle in unterschiedlichen Lösungsmitteln einzustellen. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2006/z502517_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Biofunctionalized ceramic nanowires: A reactive ester polymer has been used to immobilize silicatein, a hydrolytic enzyme involved in the biomineralization of SiO2, on the surface of TiO2 nanowires. The surface-bound protein retains its original hydrolytic properties and also acts as a reductant for AuCl4− in the synthesis of hybrid TiO2/silicatein/Au nanocomposites. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z503770_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Reversible addition fragmentation chain transfer (RAFT) polymerization of pentafluorophenyl methacrylate (PFMA) was carried out in the presence of cumyldithiobenzoate and 4-cyano-4-((thiobenzoyl)sulfanyl)pentanoic acid, respectively. These chain transfer agents with 2,2'-azoisobutyronitrile (AIBN) as initiator yielded the active ester polymer poly(PFMA) with (M) over bar (n) up to 17 000 g center dot mol(-1) and low polydispersity index ((M) over bar (w)/(M) over bar (n) < 1.2). Kinetic analysis using F-19 NMR spectroscopy and gel permeation chromatography (GPC) measurements showed controlled polymerization behavior for both chain transfer agents. Successful preparation of linear diblock copolymers consisting of an active ester block and methyl methacrylate, N-acryloylmorpholine, or N,N-diethylacrylamide, respectively, could be demonstrated. These polymers could easily react with amines in a polymer analogous reaction to form multifunctional polymers.

Pentafluorophenyl acrylate and -methacrylate were polymerized using AIBN as a thermal initiator. The obtained polymers were soluble polymeric active esters that could be used for the preparation of multifunctional polymers. The reactivity of poly(pentafluorophenylacrylate) and poly(pentafluorophenylmethacrylate) towards primary and secondary amines, as well as alcohols was investigated in a quantitative way. Both poly(active esters) reacted satisfactorily with aliphatic primary and secondary amines but only low conversion was found in the case of aromatic amines. Conversions of only 30% were reached when poly(pentafluorophenylacrylate) was treated with one equivalent of alcohol under base catalysis. In time resolved FT-IR studies the rate constants of the polymer analogous reactions were determined.