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. 2021 Oct 5;33(49):2102900. doi: 10.1002/adma.202102900

Figure 2.

Figure 2

Photorheology characterization of Gel‐NB‐based resin using 0.05% w/v LAP as photoinitiator. Unless otherwise specified, photoresins are composed of 5% Gel‐NB (DS ≈ 50%) and PEG4SH at 1:1 SH:NB molar ratio A) Thiol–ene crosslinking scheme illustration of photoresin composed of Gel‐NB and a thiolated crosslinker. Upon 405 nm excitation of LAP, the generation of radical initiation species leads to step‐growth crosslinking (top). Structures and MW of thiolated crosslinkers used in this study (bottom). B) Investigation of DS influence on final hydrogel mechanical properties. The wide DS range results in tunable hydrogel stiffness. DS of ≈3%, obtained with a Gel:CA ratio of 500:1, is also shown to be not enough to guarantee hydrogel formation. C) Investigation of Gel‐NB concentration influence on final hydrogel mechanical properties. Highest storage modulus is observed for Gel‐NB 10%. A reduction of polymer content is associated with a reduction of the final mechanical properties due to a less densely crosslinked network. D) Influence of SH:NB ratio on final hydrogel mechanical properties. The use of 5× norbornene or 5× thiols results in much weaker gels. E) Influence of different thiolated crosslinker on final hydrogel mechanical properties. The highest storage modulus is observed with PEG4SH, while a drastic reduction is shown with the use of bifunctional crosslinkers. A direct comparison between bifunctional crosslinker with different MW shows that also chain length plays an important role in determining hydrogel stiffness.