Lee Arnold Schechtman

Synthesis of high-molecular-weight poly([r]-(-)-3-hydroxybutyrate) in transgenic Arabidopsis thaliana plant cells

High-molecular-weight poly([R]-(-)-3-hydroxybutyrate) (PHB), a biodegradable thermoplastic, was produced from a suspension culture of transgenic Arabidopsis thaliana plant cells expressing two genes from the bacterium Alcaligenes eutrophus involved in the synthesis of PHB. The molecular structure of the plant-produced polymer was analysed by gas chromatography, mass spectrometry, proton nuclear magnetic resonance spectroscopy, infra-red spectroscopy, spectropolarimetry, differential scanning calorimetry, X-ray diffraction and size exclusion chromatography. The results indicate that the polymer from transgenic plants appears to have a chemical structure identical to that of PHB produced by bacteria. However, the molecular weight distribution of the plant-produced PHB was much broader than that of typical bacterial PHB.

Low temperature transmission electron microscopy and differential scanning calorimetry characterization of latexes stabilized with surface active block oligomers

Abstract The spatial distribution of a short-chain amphiphilic diblock copolymer (i.e. block oligomer), used as an emulsifier during the preparation of a latex, is determined by low temperature transmission electron microscopy and differential scanning calorimetry (d.s.c.). The main question is whether intermixing of the amphiphilic block oligomer and latex core materials actually takes place to a significant extent. Electron microscopy gives a clear indication that a surfactant-rich layer exists in all latex samples examined. At very high surfactant concentration (>6%, not typically used in commercial latexes), electron beam radiation damage reveals the presence of a surfactant gradient from the particle surface to its core. These results are in good agreement with our d.s.c. data.