Self-Activation of Poly(methylenelactide) through Neighboring-Group Effects: A Sophisticated Type of Reactive Polymer

The present work reports on a reinvestigation of a radical polymerizable lactide derivative since the polymerization properties were only poorly studied in the first publication in 1969. The optically active methylenelactide was polymerized by free radical polymerization in solution using AIBN as an initiator and resulted in isotactic-biased atactic optically active poly(methylenelactide) according to H-1 NMR and C-13 NMR spectroscopies and specific rotation angle measurements [alpha](20)(D) = -38.5 +/- 0.5 degrees. The molecular weights range between 4 x 10 (4) and 1 x 10 (5) g mol(-1) with dispersities of ca. D = 2.5 and a detected glass transition temperature of 244 degrees C. IR spectra of the polymers indicate different ester reactivities (nu(a) = 1779 cm(-1), nu(b) = 1755 cm(-1)) that can be referred to as neighboring-group effects. These highly activated esters react readily with nucleophiles in polymer analogous reactions. Thus, the aminolysis of poly(methylenelactide) was performed under mild conditions with varied amines. In the case of aminolysis with tetrahydrofurfurylamine, a nonstable cloud point in water was observed.