The copper‐catalyzed azide/alkyne cycloaddition reaction (CuAAC) has emerged as the most useful “click” chemistry. Polymer science has profited enormously from CuAAC by its simplicity, ease, scope, applicability and efficiency. Basic principles of the CuAAC are reviewed with a focus on homogeneous and heterogeneous catalysts, ligands, anchimeric assistance, and basic chemical principles. Recent developments of ligand design and acceleration are discussed.

Strategies for visualizing stress within polymeric materials are of growing interest during the past decade. In this paper, stress-sensing materials, triggered by a mechanoresponsive catalytic system based on latent copper(I)bis(N-heterocyclic carbene) mechanophores, are reported, which can be activated by compression force to trigger a fluorogenic copper(I)-catalyzed alkyne/azide "click" cycloaddition reaction, activating a fluorescent dye useful for stress-sensing applications in bulk polymeric materials. The focus is placed on the polymeric architecture, which is responsible for an efficient stress transmission, revealing the greatest activation for network-based mechanocatalysts, observing "click" conversions up to 44%, while chain-extended and linear mechanocatalysts activate either in a less efficient manner or are not completely latent in the initial state. The developed catalysts enable "irreversible" mechanochromic systems for stress-sensing devices.

We report on copper(i)-bis(N-heterocyclic carbene)s (NHC) for quantitative stress-sensing. This mechanophore is embedded within a polyurethane network, triggering a fluorogenic copper(i) azide alkyne cycloaddition (CuAAC) of 8-azido-2-naphtol and 3-hydroxy phenylacetylene.

Novel PS-based mechanophores of linear and chain-extended architecture are synthesized obtaining bis(NHC) complexes with more than one Cu(i) center per chain and molecular weights of up to 50 000 g mol−1.