**5. Conclusion**

The development of high-performance, PI-based materials by following the rigid prerequisites of environmentally benign, green, or sustainable chemistry may still seem an arduous or eccentric task to the research society, especially to the industry-related part of it. The illusive incompatibility with the petrochemicalderived starting compounds and the usually harsh experimental conditions involved in their synthesis contribute to this stance. Nevertheless, judging by the firm advances made in the field in the last decade, the concept of bio-based or green PIs is not to be outdone.

Significant research endeavors have been devoted to engineer naturally derived building blocks based on nontoxic, bio-renewable feedstocks. These have evolved as viable and accessible alternatives to the traditional starting compounds and can be subjected to the classical experimental conditions of PI synthesis or even to greener ones. In most cases, the structural motifs of natural products are tailored to attain amine functionalities, while bio-based dianhydrides are still in their infancy.

Moreover, these building blocks can unlock eco-friendly, bio-based PI materials that maintain the same combination of high-performance characteristics and even bring some new or enhanced features to the field. There is a handful of high molar mass, soluble bioPIs with thermal stability, and mechanical features comparable with (and in a couple of cases even higher than) those of analogous petroleumbased PIs. They can be processed both as films and fibrils and provide industryappealing features such as high optical transparency, optical activity, stable dielectric character, or tailorable hydrophilicity, without any negative impact upon thermal or mechanical resilience. Therefore, green polyimide chemistry exceeds the
