**2. Bio-based polyimides**

A plethora of reliable studies and publications on bio-based, green polymers have been extensively produced in the last 10 years, some of the most solid reviews on the topic being cited herein [26–28].

Various natural, eco-friendly chemical structures have been produced and used after several modifications of their chemical function to access sustainable and eco-friendly polymers. These include vanillin [29] or bio-succinic acid [30] for semi-aromatic polyesters, lignins for phenolic oligomers [31], epoxidized castor oils for thermosetting architectures [32], catechol-based moieties for highly adhesive polymers [33], biodegradable copolymers from SO2, renewable eugenol for biodegradable materials [34] or cashew nut shell liquid for various systems [35].

The development of high-performance bio-based polymers such as PIs is currently indispensable to establish the sustainable and green objective of the research society. However, its accomplishment proves a difficult task due to the incompatibility of their aromatic monomers with renewable, natural resources. PIs were built for a long time from petrochemical-derived monomers, but some recent attempts to synthesize them from bio-based monomers are chancing this trend. Among ecopolymers, PIs'synthesis starting from natural and renewable resources is not to be outdone. As in the case of already well-developed eco-friendly polymers, the chemical functions present in natural products have been modified to obtain, in the majority of cases, amine functions. Several attempts have been made to prepare partially or completely biopolyimides using bio-based aromatic diamines and various dianhydrides.

After thoroughly sweeping the available studies, we were able to find a handful of biopolyimide systems (bioPIs) based on different green or eco-friendly diamines. Some of the most important ones are described below.
