Optimum conditions for the synthesis of linear polylactic acid-based urethanes

The reactions of polylactic acid (PLA) oligomers and isocyanates (4,4'- dip henylmethane diisocyanate and toluene diisocyanate) are reported. The effec ts of the reaction conditions, that is, the reaction time, reaction tempera ture, molar ratios, isocyanates, and catalyst, on the number-average molecu lar weight (M-n) are demonstrated. The optimum reaction conditions are dete rmined by the synthesis of relatively high M-n PLA-based linear polyurethan es. The structure of the polymer samples was investigated with dynamic ligh t scattering, H-1 NMR, IR, and matrix-assisted laser-desorption ionization time-of-flight mass spectroscopy (MALDI-TOF MS). (C) 2000 John Wiley & Sons , Inc.