Photo-dimerisation reactions that can be reversed upon application of an appropriate wavelength of light have generated a considerable interest in the development of new photo-responsive polymeric systems for diverse applications. The incorporation of photo-dimerisable moieties into polymers allows the fabrication of various polymer architectures with an added advantage of reversibility. This review focuses on polymeric systems that exploit photo-reversible dimerisation reactions and their applications.

Recent developments on the synthesis and flocculation efficiency of several non-ionic, cationic, anionic and amphoteric polymers are presented and summarised.

A diamine cross-linker with thermal reversible Diels–Alder (DA) adducts of furan and maleimide groups has been designed and synthesised, which can be used to crosslink commercial epoxy monomers to achieve self-healing, cross-linked epoxy polymers. This new strategy to make self-healing epoxy polymer was successfully proved by incorporating the cross-linker with a widely used epoxy monomer, the diglycidyl ether of bisphenol A. The self-healing property of the new epoxy polymer was shown by complete elimination of cracks after the process of retro-DA and DA reactions which occurred in the cross-linker component of the network.

The usage of renewable resources has become a hot topic upon the rising global awareness against fossil feedstock consumption. Lignin, the 2^nd most abundant natural polymer on Earth, is an aromatic biomacromolecule that holds a tremendous potential for the synthesis of biobased materials. The production of monomers and polymers from lignin has been investigated for years and keeps on expanding, as proven by the flourishing literature. However, the sustainability of the synthetic reactions has not been systematically analyzed. Herein, green chemistry plays a vital role in this area and provides several tools to design eco-friendly production methods. This critical review first describes the preeminent approaches for the synthesis of biobased monomers and polymers from lignin-derived compounds. In the second part, the “greenness” aspects of the 175 key monomer synthetic methods and 32 polymerization methods are evaluated based on selected criteria, including waste generation, atom efficiency, energy efficiency, usage of safer solvents, and biocatalytic methodology. The accessible green metrics, such as environmental factor (E factor) and atom economy are calculated to measure the greenness and to provide a quantitative base for strategic decisions. Furthermore, this study provides insights for the improvement opportunities and lights up the room for further developments. This review, aiming at scientists, industries and investors, strives to provide a critical outlook for the existing synthetic methods and motivates researchers to call for the integration of sustainability factors.