Nevertheless, our data suggests that thiol-ene hydrogels can bond strongly to reactive elastomers and surfaces presenting alkene or thiol residues. This opens interesting opportunities to promote bonding with other cell instructive thiol-ene hydrogels, which are increasingly proposed as soft matrices for cell encapsulation and the regeneration of soft tissues 1, 2, 10 , to more rigid polyesters that are typically applied to the regeneration of stiffer tissues, such as bone . As a proof-of-concept, we explored the bonding of poly(e-caprolactone) samples to PDMAEMA-Pent hydrogels. Poly(e-caprolactone) substituted with propargyl residues was synthesised by post-polymerization modification of PCL according to protocols previously published . Samples were then solvent cast into moulds, cut and formulated into PDMAEMA-Pent based hybrids. Within the range of polymer concentrations tested, failure was found to be cohesive (Figure ) and the ultimate tensile stress linearly increased, presumably reflecting the gradual increase in gel modulus expected and apparent Young's modulus measured (Figure ). Despite the excess alkene residues in the gel phase and presence of alkynes alone in the PCL phase, the ultimate stress achieved remained comparable to that of hybrids formulated with the same gel composition and thiol-ene PDMS (compare Figure to Figure ). This is in agreement with the cohesive failure characteristic of both series of hybrids and indicate that strong bonding occurs between thiol-ene and thiol-yne networks, irrespective, to some level, of the position of the balance of moieties on both sides of the interface. To confirm the strength of thiol-ene bonding even with non-matched interfaces (alkyne excess in PCL and alkene excess in the gel), we imaged the interface of corresponding hybrids after failure, via cryo-SEM (Figure ). This clearly showed well integrated interface with no apparent crack suggesting partial delamination. This is an interesting feature as it suggests that thiol-ene interfaces are relatively permissive in terms of formulation of the gel and elastomer/hydrophobic phases, which should allow greater flexibility of design of corresponding materials and mechanical properties.