Anionic graft polymerization of methyl methacrylate on starch and dextrin

The anionic graft polymerization of methyl methacrylate on the potassium alkoxide derivative of starch or dextrin in DMSO was studied. The effects of monomer and alkoxide concentrations as well as temperature were investigated. The yield of graft polymer increased with increasing alkoxide concentration. With increasing monomer concentration and with increasing temperature the extent of homopolymer formation increased. The composition of the graft polymers was found to depend on the reaction conditions. Graft polymers having about 10–40% poly(methyl methacrylate) were obtained. There were quantitative differences in yield of isolated graft polymer between starch and dextrin and these were ascribed to differences in the solubility properties of the carbohydrates. Evidence on the structure of the graft polymers and on the mechanism of the graft polymerization was obtained from acid hydrolysis of the graft polymers and determination of the molecular weights of the cleaved side chains.     

Block copolymers of isotactic polypropylene and 1,4-polybutadiene

Two block copolymers of isotactic polypropylene and 1,4 polybutadiene were synthesized using techniques involving a transformation from anionic to Ziegler–Natta polymerization mechanisms. The yield of block copolymer was about fifteen percent (weight basis) in both polymerizations, the remainder being unreacted polybutadiene from the first block synthesis. Molecular characterization experiments and model reactions were consistent with a block-like structure for the copolymers; definitive evidence for the proposed molecular structure was obtained through transmission electron microscopy which clearly revealed microphase-separated morphologies characteristic of block copolymers.     

Determination of higher molecular weight aliphatic aldehydes and ketones

The visible absorption spectra have been measured for the reaction products formed by aldehydes and ketones with p-nitrobenzenediazonium fluoborate in a phosphoric acid-2-methoxyethanol solvent medium. The absorption maxima for the reaction products of higher molecular weight aldehydes and ketones are much more intense than those formed by formaldehyde, acetaldehyde and acetone. This intensity effect has been used to analyze for propionaldehyde in mixtures also containing formaldehyde, acetaldehyde or acetone. The nature of the reaction products are considered.     

Influence of NaCl on the behavior of PEO-PPO-PEO triblock copolymers in solution, at interfaces, and in asymmetric liquid films

The solution behavior of the polymeric surfactant Pluronic F127 (PEO(99)PPO(65)PEO(99)) and its adsorption behavior on aqueous-silica and aqueous-air interfaces, as well as the disjoining pressure isotherms of asymmetric films (silica/aqueous film/air) containing F127, are studied. The interfacial properties of adsorbed F127 layers (the adsorbed amount Gamma and the thickness h) as well as the aqueous wetting film properties [film thickness (h) and refractive indexes] were studied via ellipsometry. The solution properties of F127 were investigated using surface tensiometry and light scattering. The interactions between the air-water and silica-water interfaces were measured with a thin film pressure balance technique (TFB) and interpreted in terms of disjoining pressure as a function of the film thickness. The relations between the behaviors of the asymmetric films, adsorption at aqueous air, and aqueous silica interfaces and the solution behavior of the polymeric surfactant are discussed. Special attention is paid to the influence of the concentrations of F127 and NaCl. Addition of electrolyte lowers the critical micelle concentration, diminishes adsorption on silica, and increases the thickness of the asymmetric film.     

Photochemie organischer Festkörper

In den Jahren seiner Tätigkeit am Weizmann Institut of Science begann G. M. J. Schmidt seine Arbeiten über die Beziehungen zwischen der Struktur organischer Kristalle und der in ihnen stattfindenden chemischen Reaktionen, ein Forschungsvorhaben, das sich in der Folge als außergewöhnlich fruchtbar erwiesen hat. So wuchs seine ?Festkörper-Gruppe”? und wurde divergenter - Röntgenstrukturanalytiker, Organiker, Spektroskopiker und schließlich sogar Theoretiker wirkten mit. Professor Schmidt starb 1971. Als eines der Mitglieder dieser Gruppe folge ich nun der Einladung, über neuere Entwicklungen auf meinem Interessengebiet zu berichten. Ein Großteil der bisher untersuchten Reaktionen organischer Kristalle wird durch Licht oder andere Strahlung induziert. Dies ist eine natürliche Folge davon, daß Strahlung, ungleich den meisten chemischen Reaktanden, leicht die Oberfläche des Kristalls durchdringen und so die zu aktivierenden Orte erreichen kann. In diesem Beitrag sollen einige der in der Photochemie organischer Kristalle wirksamen Prinzipien aufgezeigt und anhand von Beispielen verdeutlicht werden, wobei nicht beabsichtigt ist, alle bisher untersuchten unterschiedlichen Reaktionstypen und Systeme zu erfassen. Es ist geboten, hier in Anerkennung auch eines anderen großen Wissenschaftlers zu gedenken, der vor kurzer Zeit verschied - Theodor Förster. Manche der Ideen, auf die ich im folgenden eingehe, wurzeln, wie so vieles in der jüngsten Entwicklung der Photochemie, in Professor Försters früheren Arbeiten.