Preparation and characterization of biodegradable condensation polyimide

Various biodegradable polyimides (bio-PI) were successfully synthesized and investigated in this study. First, biodegradable oligomer, amine terminated poly (propylene fumarate) (PPF-NH2), was preliminarily synthesized from poly (propylene fumarate) oligomer (PPF) and 3-chloropropylamine hydrochloride. The resulting PPF-NH2 was subsequently used to react with equal mole ratio of 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (s-BPDA) in the solvent to generate biodegradable poly (amic acid) (bio-PAA) through condensation reaction. A final product of biodegradable polyimide (bio-PI) was successfully obtained by immidization of bio-PAA at a low-temperature (120 °C) under the vacuum condition. A 3-component system of biodegradable polyimide (3C-bio-PI) was also synthesized by replacing different level of PPF-NH2 by 4,4′-oxydianiline (4,4′-ODA) in previously mentioned bio-PI.The biodegradation characterizations of the various bio-PIs (including 3C-bio-PI) were performed with phosphate buffer solution. Morphological changes for the biodegraded surface of the various bio-PI films were apparent after buffer solution test. Mechanism of morphological changes for the biodegraded surface is also proposed in this work. The bio-PI film synthesized from equal mole ratio of PPF-NH2 and s-BPDA was biodegraded more quickly than the 3-component system of biodegradable PI film incorporated with 4,4′-ODA.The thermal properties of various bio-PIs are slightly inferior to those of regular PI; however, it is comparable to those of regular PI. The mechanical property of various bio-PIs is a little worse than that of regular PI, but it's still in the same order of magnitude.