Step-growth polymerization and ‘click’ chemistry: The oldest polymers rejuvenated

Since its discovery in 2001, copper catalyzed azide–alkyne ‘click’ chemistry has been extensively used in polymer chemistry to modify polymeric materials and create advanced polymer structures by efficient coupling reactions. Surprisingly, the contribution of this Huisgen cycloaddition reaction to industrially important commodity polymers, prepared by step-growth polymerization, was not existing until recently. Nevertheless, since many decades academic and industrial research was focused on finding attractive synthetic pathways to introduce large contents of different reactive functional groups in several polymer classes such as polyesters and polyurethanes. Because of the high tolerance of azide–alkyne coupling reactions to a wide variety of functional groups and to extreme reaction conditions often used in step-growth polymerizations, the straightforward synthesis of alkyne-containing building blocks created an ideal platform to modify and broaden the physico-chemical properties of step-growth polymers by choosing readily available low and high molecular weight azide components. This feature article provides a comprehensive review covering the strategies toward ‘click’-functionalization of several classes of industrially important step-growth polymers.