Some multicomponent reactions (MCRs) are similar to click reactions to give highly selective products with reliable high yield and effective atom utilization, implying that they can also be recognized as click reactions. The addition of mercaptoacetic acid to an imine bond can be considered as a clickable MCR since this catalyst free reaction can occur smoothly under benign conditions in a short time with water as the only byproduct. This reaction has thus been introduced into polymer chemistry and different functional polymers have been successfully synthesized through modification of polymer chain-ends, linkage of two polymer chains and polycondensation.