In a chain-growth radical propagation reaction, as in the photocrosslinking of HA-MA, the diffusion of the chains is hindered as gelation proceeds and termination is slowed down. As a result, the lifetime of the propagating radicals exceeds the illumination time and the crosslinking reaction can continue after exposure. This has previously been demonstrated in 30% w/v Pluronic/Pluronic diacrylate hydrogels where the shear storage modulus increases after UV exposure showing postexposure polymerization of the polymer chains. In a photoinitated step-growth radical reaction, the situation is different. To quantify post-exposure reactivity of HA variants, we monitored the crosslinking during step-wise exposure with 400-500-nm light at 15 mW cm -2 (Figure ). Thiolene crosslinked hydrogels showed a rapid increase of G' during the illumination periods and did not show any further variation of G' during the dark periods, indicating that the crosslinking starts and stops with the light exposure. In contrast, the storage modulus the HA-MA system continued increasing after the light was switched off throughout the whole 40-s dark phase. The post-exposure crosslinking in HA-MA limits the possibility to control the crosslinking process in time and space.