Effect of PBA-Ac concentration on the viscoelastic properties of boronate hydrogels. (a) Frequency sweep of tan δ for hydrogels functionalized with PBA-Ac at 0 mM (purple circle, Ela), 50 mM (green diamond, PBA-50), 100 mM (red triangle, PBA-100), and 200 mM (blue triangle, PBA-200). (b) Frequency sweep of hydrogels functionalized with tethered trans-vic-diols (GluAc, 200 mM) and PBA (0 – 200 mM). (c) Frequency sweep of hydrogels functionalized with tethered cis-vic-diols (ManAc, 200 mM) and PBA (0 – 200 mM). (d) The tan δ (10 rad s−1) of hydrogels functionalized with PBA-only (green), trans-vic-diols (red, GluAc), and cis-vic-diols (black, ManAc) increase as a function of tethered PBA-Ac concentration. Data points represent the average measurement of three samples ± SD.