No abstract

4-Vinylpyridine (4VP) and N,N-dimethylacrylamide (DMAA) were polymerized in a controlled manner using a β-phosphonylated nitroxide (N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide, commonly designated as DEPN) as a control agent. Compared to the results that had previously been reported for the nitroxide-mediated radical polymerization (NMRP) with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), the polymerization of 4VP was much faster and very well controlled up to higher monomer conversions. Unlike 4VP, the controlled radical polymerization of DMAA using different types of nitroxides had so far remained limited to a very low conversion range (typically inferior to 10%). The use of DEPN gave rise to a very significant improvement of the NMRP of DMAA by providing a good reaction control up to high conversion (approximately 60%). For the first time, the ability of DEPN to control the homopolymerization of DMAA even at high conversion allowed the synthesis of poly(DMAA-b-4VP) block copolymers with a hydrophilic poly(DMAA) block which was longer than the poly(4VP) block. This particular feature should fairly improve the hydrosolubility of the derived amphiphilic cationic polymers, which can be obtained by simple quaternization of the former block copolymers, and extend the scope of their applications.

It has been found that sulfur dioxide solubility in organic solvents can be well-correlated by Lewis basicity numbers. Mixtures of sulfur dioxide and solvent (N-methylpyrrolidone (NMP), N,N′-(dimethylpropylene)urea (DMPU) and methyldiethanolamine (MDEA)) have been prepared in a 1:1 mole ratio at low temperatures. The melting points of the mixtures are measured, and the mixtures have been analyzed by infrared, ultraviolet-visible, and nuclear magnetic resonance spectroscopy. The solubility of sulfur dioxide has been measured in NMP and DMPU at 25 °C. At sulfur dioxide concentrations of 0.2-0.6 kPa, the solubility is determined using a continuous stirred tank reactor. The absorption of sulfur dioxide proved to be completely reversible. A model where physical and chemical interactions are incorporated showed good correlation with the experimental results.