Using a ''never-dried'' procedure (according to Figure 4) shaped bacterial nanocellulose (BC, 1% cellulose, 99% water) has been modified by the formation of BC-polymer composites. For this purpose, acrylate and methacrylate monomers and methacrylate crosslinkers were photopolymerized inside an ethanol-swollen nanofiber network. Using the ethanol as solvent and as confirmed by model reactions the synthetic polymer (SP) part of the composites is constructed of crosslinked polymers (number of repeating units in the range of 500). As part of ongoing work on the development of (bio)materials from the innovative pool of BC composites these investigations are recently directed towards the creation of collagen-like materials. Thus, for these purposes, mainly water absorption capacity, strength, and elasticity have to be controlled, whilst still retaining essential features of BC like shape, nanofiber network, pore system, and proved biocompatibility. Using acrylic acid, 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, N-vinyl pyrrolidone as acrylate monomers and triethylene glycol dimethacrylate and 1,4-butandiol dimethacrylate as crosslinkers of different concentrations either a filling of the pores or a coating of the fibers in the BC nanocomposites could be achieved. The small cellulose content of the composites significantly increases the water absorption value and the strength of the material as well as the ability of re-swelling in the case of fiber coated composites. Sample 12 is an optimized BC-SP composite regarding important properties of hyaline cartilage like Young's modulus in the range of 5-20 MPa using the well-known Simplex-method.

Structural investigations of low-molecular-weight polyisobutenes synthesized by selective polymerization and of commercial polyisobutenes were made by 'H-and "C-NMR spectroscopy. It is possible to attribute the signals to "normal" and to some unusual olefinic structures. A comparison was made to literature data. ZUSAMMENFASSUNG:Mittels 'H-und I3C-NMR-Spektroskopie werden Strukturuntersuchungen an Polyisobutenen, die durch Selektivpolymerisation hergestellt wurden, und an Handelsprodukten durchgefuhrt. Es ist moglich, die Signale "normalen" und einigen ungewohnlichen Doppelbindungsstrukturen zuzuordnen. Die Ergebnisse werden mit Literaturdaten verglichen.

Low molecular weight polyisobutenes can be transformed into macromonomers by means of SH-en addition, provided that the thiols contain an additional hydroxy group. The product structures formed by free-radical or electrophilic addition reactions can be determined on model compounds as well as on the polymers by 'H-and I3C-NMR spectroscopy. ZUSAMMENFASSUNG:Aus niedermolekularen Polyisobutenen konnen durch SH-en-Addition radikalisch polymerisierbare Makromonomere hergestellt werden, wenn die Thiole zusatzlich iiber eine Hydroxy-Funktion verfugen. Die durch radikalische oder elektrophile Additionsreaktion entstehenden Produktstrukturen lassen sich sowohl an den Modellverbindungen als auch an den Polymeren mittels 'H-und I3C-NMR nachweisen.

Investigations on the Charge-Transfer Interaction of Phenols with Tetracyanoethylene (TCNE)The donor properties of some phenol derivatives were determined by measuring the UV/Vis spectra of their CT complexes with tetracyanoethylene in 1,2-dichloroethane and acetonitrile at room temperature. The ionization potentials of the phenolic compounds have been calculated by using the longest visible charge-transfer absorption of the donor-acceptor complex by linear correlation analysis. The charge-transfer spectra are discussed in dependence on the ring substituents in terms of electronic and steric factors. Increasing donor strength of the substituents decreases the ionization potential of the phenols as demonstrated by an LFE relationship using the Hammett constants. However, orfho donor substituents enhance the donor strength of the aromatic ring as well.

Radically polymerizable macromonomers were synthesized by alkylation, epoxidation and SH-en addition of low-molecular-weight polyisobutenes followed by esterification with methacrylic acid derivatives. Highly functionalized products (1 95%) can be obtained from polyisobutenes with double bond content G 1 by separation of non-functionalized polymer by column chromatography. ZIJSAMMENFASSUNG:.Auf der Basis niedermolekularer Polyisobutene wurden durch Alkylierung, Epoxidierung und SH-en-Addition sowie anschliel3ende Veresterung mit Methacrylsaiirederivaten radikalisch polymerisierbare Makromonomere hergestellt. Durch chromatographische Abtrennung unfunktionalisierter Polyisobutenanteile konnen hochfunktionalisierte Produkte (2 95%) auch aus Polyisobutenen erhalten werden, welche Doppelbindungsgehalte 4 1 aufweisen.