(A) Designation of chemical moieties for synthetic scheme. (B) Synthetic scheme for lithium phenyl-2,4,6-trimethylbenzoylphosphinate photoinitiated polymerization of (poly)ethylene glycol diacrylate (PEGDA) and 2-carboxylethyl acrylate (CEA) as described in more detail in the SI. (C) In situ rheometry of particle conditions B, C, and D. Condition A too rigid to be tested in situ. (D) Swollen shear moduli of particle conditions A–D, statistics displayed represent comparison to A. (E) Equilibrium swelling ratios of particle conditions A–D, where (*s) indicate significance within hydrogel types to A and (#s) indicate difference between water and plasma. (F) Synthesis compositions and calculated bulk material properties of hydrogels.27 Statistical analyses were performed using one- and two-way ANOVA with Fisher’s LSD test, where (*) indicates p<0.05, (**) indicates p<0.01, and (***) indicates p<0.001, (****) indicates p<0.0–01 and (####) indicates p<0.0001. Error bars represent standard error.