Synthesis of photoresponsive cyclic poly(dimethyl siloxane)s from monodisperse linear precursors

摘要

Polysiloxanes are industrially important silicon-based polymeric materials which cannot be replaced by carbon based ones. In this area, synthesis of well-defined functional poly(dimethyl siloxane) (PDMS) with nonlinear macromolecular architectures is indispensable for finding next-generation applications. Here we report the synthesis of cyclic PDMS (C) with photocleavable and reformable hexaarylbiimidazole (HABI)-derived covalent bonds in the main chain from triphenylimidadole (lophine) end-functionalized monodisperse linear precursors (Ls). Interestingly, an end-to-end cyclization reaction of L with the concentration (10 mg/mL) much higher than that of a typical concentration (similar to 0.1 mg/mL) dominantly produced unimolecularly cyclized product. Moreover, photoirradiation to C under a solvent-free condition, molecular weight increased despite the physical state of C was solid.