Anionic polymerization of propylene oxide and its kinetics

The polymerization of propylene oxide in hexamethyl phosphoramide (HMPT) was investigated with potassium t-butoxide as initiator. Monodisperse poly (propylene oxide) was obtained (PDI=1.04), then infrared spectroscopic (IR) and hydrogen nuclear magnetic resonance spectrum (1H-NMR) were used to characterize its structure, all the peaks in 1H-NMR spectra was assigned as well. Number average molecular weight was calculated by 1H-NMR and was limited to about 2800. Chain-transfer constants were calculated out and were found to increase with the molar ratio of propylene oxide to potassium t-butoxide, which may be lead to the upper limit of molecular weight. In-situ FT-IR spectroscopy was used to illustrate the anionic polymerization of propylene oxide. According to the calibration of absorbance to concentration, activation energy was worked out to be 38.0 kJ/mol and the kinetic equation was deduced to be.