The linear relations and living feature in cationic ring-opening copolymerization of epoxy/THF system

The cationic copolymerization of diglycidyl ether of bisphenol-A with tetrahydrofuran (THF) initiated by phosphotungstic acid H₃PW₁₂O₄₀ (PW₁₂) was in situ investigated by Fourier transform near infrared spectroscopy. The gelation point of the reaction was determined by rheometrics mechanical spectroscopy. It was found that the conversion of epoxy group at 4,530 and 6,073 cm^?1 increased linearly with reaction time up to a high conversion (~90%), during which gelation (at ~51%) had no effect. The slope-indicating reaction rate of epoxy group also increased linearly with the content of PW₁₂. In addition, the peak splitting pattern of the overlapping C–H vibration region (5,700–6,200 cm^?1) was developed here. The peak-splitting analysis showed that the epoxy behavior agreed with above results, but the reaction rate of THF slowed down gradually with reaction time as the viscosity of the system increased. The results suggest that the kinetic behavior of cationic polymerization shows living feature of the propagating chains in this system and near infrared (NIR) technology could be applied to study such kinetic behavior.