Finally, the effect of more reactive nucleophiles on crosslinking were investigated by replacing EDA with EDT and keeping the mol% epoxide constant (Figure ). Thiols are known to be stronger nucleophiles than primary amines, and the ring opening reaction between thiols and epoxides proceeds orders of magnitude faster than between amines and epoxides . At a constant 1 M epoxide concentration, poly(GMA-co-MEMA) with EDT crosslinked more rapidly (30 min) than the amine condition and attained a similar final G'. Poly(GMA-co-PEGMA500) samples crosslinked rapidly (42 min) with EDT, but more slowly than the MEMA copolymer and attained a final modulus on the order of 10 4 Pa. Poly(GMA-co-PEGMA950) samples still did not show any signs of gelation, increasing only to a final modulus of 10 Pa. Even with faster reaction kinetics, the PEGMA950 shielding groups suppress gelation.