Diels-Alder (DA) reaction between N-phenyl maleimide and the pendant furan ring of the CO2 and furfuryl glycidyl ether copolymer (PFGEC) was employed for stabilization of PFGEC by reducing the amount of furan ring and introducing bulky groups into PFGEC.The stability of the product was enhanced by increasing the cyclization degree

the PFGEC with cyclization degree above 70% was air stable.Optimal reaction conditions were obtained

taking the N-phenyl maleimide as an example

cyclization degree as high as 84.1% was realized when the DA reaction was carried out in dimethyl carbonate at 60℃ for 24 h with molar ratio of N-phenyl maleimide to furan ring of 3∶1. The DA reaction was endothermal reaction

raising reaction temperature generally can raise cyclization degree

however

DA reaction was also a reversible process

when the temperature was high enough

reverse reaction (r-DA) existed

e.g.

when the DA product of PFGEC with cyclization degree of 72.1% was heated in dimethyl sulfoixde solution at 100℃ for 10 min

the cyclization degree decreased to 40.4%

indicating that the r-DA reaction proceeded quite fast at temperatures above 100℃.