Photocleavable Regenerative Network Materials with Exceptional and Repeatable Viscoelastic Manipulability.

The development of solventless system for modulating properties of network materials is imperative for the next generation sustainable technology. Utilization of photostimulation is important owing to its spatial and temporal locality, yet designing photoresponsive network materials exhibiting repeatable and dramatic change in their properties remains a challenge. Here, the authors report a photocleavable regenerative network (PRN) linked with photoresponsive hexaarylbiimidazoles (HABIs) synthesized from narrow dispersity star-shaped poly(dimethylsiloxane)s (PDMSs) having 2,4,5-triphenylimidazole end groups. The use of urea anion as a catalyst for ring opening polymerization (ROP) of cyclic siloxane initiated from silanols enables control of molecular weight and dispersity. The rheological measurements for the synthesized PRNs exhibit drastic changes in storage and loss moduli (G' and G″) upon photoirradiation in the solid state (G' > G″). This photocontrolled change in viscoelasticity with retaining solidity enables application of PRNs as a remotely-controlled photo-melt adhesive and photo-scissible string. The developed PRNs will enable a wide variety of applications such as industrially important next-generation sustainable adhesive, sealant, and reversibly-deformable 3D printing materials with their spatially and temporally local manipulability, solventless handleability, and excellent reversibility.