Developing biobased and degradable polyazomethines from hemin

Abstract

The development of biobased polymers is emerging as a critical issue for researchers in this era, especially for conjugated or semiconducting polymers, due to the lack of natural conjugated building blocks. In addition, it is of urgent importance to develop degradable polymers to diminish the increasing amount of plastic waste. Therefore, we aim to utilize hemin-based materials as a building block to develop semi-conjugated, degradable, and biobased polymers in this study. Accordingly, hemin derived from bovine is modified to remove the ferric ion and functionalize with amine or aldehyde groups. The aldehyde-functionalized protoporphyrin is copolymerized with p-phenylenediamine, 2,7-fluorenediamine, and amine-functionalized protoporphyrin to form a series of polyazomethines of PDA, FDA, and PPIX. The semi-conjugated polyazomethines exhibit varied electrostatic potential distributions and frontier energy levels based on their compositions; in addition, all the polyazomethines present high biobased contents spanning the range of 60–80%. Notably, PPIX can be rapidly depolymerized by acid hydrolysis with 0.01 mol L−1 of HCl within several hours, guaranteed by the evolutions of optical absorption and size-exclusion chromatography, which show that the polyazomethines degrade to monomers to short-chain oligomers. In the aspect of the optoelectronic device application, the semi-conjugated characteristics of the hemin-based polyazomethines give rise to their high performance as a photoresponsive polymer electret in photonic transistor memory. By fine-tuning the molecular structure and energy levels, the developed polyazomethine of FDA achieves decent data discernibility and long-termed cyclic operation as a component of memory electronics, thereby rendering green electronics exceptionally economical and environmentally feasible.