Dotsevi Y. Sogah

Bio: Dotsevi Y. Sogah is an academic researcher from Cornell University. The author has contributed to research in topics: Polymerization & Radical polymerization. The author has an hindex of 27, co-authored 53 publications receiving 3663 citations.

Group-transfer polymerization. 1. A new concept for addition polymerization with organosilicon initiators

Abstract: Polymerisation du methacrylate de methyle avec l'acetal de dimethylcetone methyl trimethylsilyle. Reaction rapide a temperature ambiante conduisant a un polymere vivant de distribution etroite de la masse moleculaire, avec rendement quantitatif

Group transfer polymerization - polymerization of acrylic monomers

Abstract: Polymerisation vivante de methacrylates en presence de cetene silyl acetals comme amorceurs et fluorure, bifluorure, cyanure ou azide comme catalyseurs

Oxyanions catalyze group-transfer polymerization to give living polymers

Abstract: Les oxyanions (carboxylate, phenolate, sulfinate...) dont le pKa dans le DMSO est compris entre 4,5 et 23, presentent une activite catalytique dans la polymerisation du methacrylate de methyle. L'influence des conditions de reaction sur la polydispersite et le caractere vivant des polymeres est etudiee. Les complexes des oxyanions avec leur acide conjugue sont egalement actifs

Self-assembly of beta-sheets into nanostructures by poly(alanine) segments incorporated in multiblock copolymers inspired by spider silk.

Abstract: Selective replacement of the amorphous peptide domain of a spider silk with poly(ethylene glycol) gave N. clavipes silk-inspired polymers having similar solid-state structures and very good mechanical properties. The tendency of poly(alanine) having appropriate chain length to form β-sheets and the facility with which the β-sheets self-assemble have been retained in the polymers. Solid-state 13C NMR, solid-state FTIR, X-ray diffraction, and AFM studies showed that the polymers formed predominantly antiparallel β-sheets that self-assembled into discrete nanostructures. The longer the peptide segment was, the greater was the tendency to self-assemble into antiparallel β-sheet aggregates. AFM revealed that the morphology of the polymers was a microphase-separated architecture that contained irregularly shaped 100−200 nm poly(alanine) nanodomains interspersed within the PEG phase. The results suggest that the poly(alanine) domain influences the solid-state properties of spider silk through β-sheet self-assemb...

Polymer-layered silicate nanocomposites: preparation, properties and uses of a new class of materials

Abstract: This review aims at reporting on very recent developments in syntheses, properties and (future) applications of polymer-layered silicate nanocomposites. This new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation, may be prepared via various synthetic routes comprising exfoliation adsorption, in situ intercalative polymerization and melt intercalation. The whole range of polymer matrices is covered, i.e. thermoplastics, thermosets and elastomers. Two types of structure may be obtained, namely intercalated nanocomposites where the polymer chains are sandwiched in between silicate layers and exfoliated nanocomposites where the separated, individual silicate layers are more or less uniformly dispersed in the polymer matrix. This new family of materials exhibits enhanced properties at very low filler level, usually inferior to 5 wt.%, such as increased Young’s modulus and storage modulus, increase in thermal stability and gas barrier properties and good flame retardancy.

Evolution of Asian monsoons and phased uplift of the Himalaya–Tibetan plateau since Late Miocene times

Abstract: The climates of Asia are affected significantly by the extent and height of the Himalayan mountains and the Tibetan plateau1,2,3,4 Uplift of this region began about 50 Myr ago, and further significant increases in altitude of the Tibetan plateau are thought to have occurred about 10–8 Myr ago4,5, or more recently However, the climatic consequences of this uplift remain unclear Here we use records of aeolian sediments from China6,7 and marine sediments from the Indian8,9,10 and North Pacific oceans11 to identify three stages of evolution of Asian climates: first, enhanced aridity in the Asian interior and onset of the Indian and east Asian monsoons, about 9–8 Myr ago; next, continued intensification of the east Asian summer and winter monsoons, together with increased dust transport to the North Pacific Ocean11, about 36–26 Myr ago; and last, increased variability and possible weakening of the Indian and east Asian summer monsoons and continued strengthening of the east Asian winter monsoon since about 26 Myr ago The results of a numerical climate-model experiment, using idealized stepwise increases of mountain–plateau elevation, support the argument that the stages in evolution of Asian monsoons are linked to phases of Himalaya–Tibetan plateau uplift and to Northern Hemisphere glaciation