Chemically Recyclable Chiral Degradable Polymers of Unsymmetrical 7-Membered Cyclic Monomers by Ring-Opening Metathesis Polymerization

A chiral degradable polymer was synthesized by ring-opening metathesis polymerization (ROMP) from an unsymmetrical 7-membered cyclic acetal chiral monomer. Chiral acetal-containing monomers were prepared using Pd-catalyzed asymmetric hydroalkoxylation of alkoxyallenes and ring-closing metathesis. The exact head-to-tail structured chiral polymer was obtained by ROMP without any side reaction. The resulting polymer was completely depolymerized into the corresponding cyclic monomer by ring-closing metathesis due to the low ring strain of the monomer, and we observed the conservation of stereochemistry of the chiral monomer during metathesis polymerization and depolymerization reactions. The degradation of the resulting acetal-backboned polymer was studied at various acid concentrations to control its degradability. Additionally, the alkyne tether moiety enabled postmodification using click chemistry.