Masako Yoshikuni

Polymerization of methyl methacrylate by tri-n-butylborane in the presence of amino acid esters☆

Abstract The polymerization of methyl methacrylate by tri-n-butylborane in the presence of amino acid esters was investigated. The binary systems of tri-n-butylborane and amino esters were found to be more effective for initiating the polymerization than tri-n-butylborane alone. Co-catalytic effects of amino acid esters were in the order: tyrosinate > glutamate > aspartate ⪢ phenyl alaninate > serinate > glycinate. The rate of polymerization in a mixture of dimethylsulphoxide and toluene was proportional to the square root of the concentration of the initiator system, to the monomer concentration, and to the concentration of dimethylsulphoxide in the solvent. The overall energy of activation was estimated to be 4.6 kcal/mol for the tri-n-butylborane/methyl tyrosinate system. Copolymerization curves gave a typical free-radical character.

Highly controlled side-chain chromophore orientation in poly[N5-1-(1-pyrenyl)ethyl-L-glutamines]

Abstract Poly[N5-(R and S)-1-(1-pyrenyl)ethyl- l -glutamines] (1 and 2) were prepared by condensation of poly( l -glutamic acid) with optically resolved amines. In solution, these polymers, 2 in particular, gave large circular dichroism (CD) indicative of exciton coupling among the side-chain pyrene chromophores. When compared with the corresponding polymer with achiral side groups, i.e. poly(1-pyrenylmethyl- l -glutamine) (3), 1 and 2 not only gave much stronger CD, but also gave much reduced excimer emission with a significant hypsochromic shift of emission maximum. The highly controlled orientation of the side-chain chromophores is apparently brought about by the specific steric interactions among the bulky chiral side chains along the helical main chain.

Polymerization of Methyl Methacrylate Initiated byjributylborane-Pyridine System

The polymerization of methyl methacrylate (MMA) by the catalysts systems of tributylborane (TBB) with pyridine and its derivatives, such as hydroxypyridine, cyanopyridine, nicotinic acid, nicotinamide, nicotinic ester, picoline, lutidine and quinoline was studied. The relative initiating activities of the pyridine and its derivatives were found to be in the following order: nicotinic acid> nicotinic ester> nicotinamide> pyridine>3-hydroxypyridine>3-cyanopyridine> quinoline > 3-picoline > acridine > 2, 6-lutidine In the polymerization of MMA initiated by TBB/methyl nicotinate (MN) system, the rate of polymerization was found to be proportional to the concentration of MMA and to the square root of TBB/MN concentrations, respectively, and the apparent activation energy was 4.1 kcal/ mol. And the reaction of TBB with pyridine was also studied by NMR and ESR methods. From these results, it was found that the polymerization proceeds via a radical mechanism involving a co-ordination between TBB and pyridine or its derivatives.