The Effect of End Group and Molecular Weight on the Yellowness of Polyetherimide

The effects of end group and molecular weight on the yellowness of telechelic polyetherimide (PEI) are investigated. Electron-withdrawing dianhydride end groups reduce the yellowness and increase the transparency of PEI regardless of the molecular weight. Electron-donating phenyl, amine, and phthalic end groups increase the yellowness of PEI but the effect depends on the molecular weight. As the molecular weight is increased, the yellowness of PEIs with electron-donating end groups initially decreases due to a decreasing end-group density and then increases due to an increasing probability of charge-transfer complex formation. The systematic study reveals the correlations among yellowness, end group, and molecular weight of PEIs. The correlations can be used for designing highly transparent PEIs and other high-performance polymers.