Fig. 3. Mechanism of PPSU dynamic network self-assembly.

a Slow hydration leading to the crystalline framework. The PPSU₂₀ hydrogel (colored by rhodamine B) was prepared by aging a DMSO solution of PPSU₂₀ (200 mg mL⁻¹) in humidity for 3 days. Adding an excess amount of water on the top of the gel allows slow solvent replacement for dense sulfone–sulfone bonding, which induces crystallization. b WAXD patterns for the humidity-induce gel, crystalline framework, and for comparison the powdered solid PPSU_20. c–d CGMD simulation snapshots showing the formation of bundles by rigid chains and a spherical hydrogel by flexible chains. Oxygen atoms are represented by the white spheres. e Collapse of PPSU₂₀ networks as indicated by the decreasing nanogel size upon stepwise hydration. Error bars represent the standard deviation from three parallel experiments. f Collapse of PPSU₂₀ assemblies enabling FRET from bisbenzimide to rhodamine 6 G. Bisbenzimide (0.01 mg mL⁻¹) and rhodamine 6 G (0.01 mg mL⁻¹) were added to 1 mL of DMSO solution of PPSU₂₀ (5 mg mL⁻¹), followed by fluorescence titrations of the system with water (50 μL per step, E_x = 375 nm).