This contribution reports the efficient conversion of γ-valerolactone and its derivatives, abundant but unexplored renewable feedstocks, into sustainable and degradable polythioesters via the establishment of the first isomerization-driven ring-opening polymerizations (IROPs) of corresponding thionolactone intermediates. The key to this success relies on the development of a new simple and robust [Et 3 O] + [B(C 6 F 5 ) 4 ] À cationic initiator which possesses high activity, exclusive selectivity, living nature, and broad scope of thionolactones. A complete inversion of configuration during IROP of enantiopure γ-thionovalerolactone is also disclosed, affording isotactic semicrystalline polythioesters (T m = 87.0 °C) with mechanical property compared well to the representative commodity polyolefins. The formation of a highly crystalline supramolecular stereocomplex with enhanced thermal property (T m = 117.6 °C) has also been revealed.

This contribution reports the efficient conversion of γ‐valerolactone and its derivatives, abundant but unexplored renewable feedstocks, into sustainable and degradable polythioesters via the establishment of the first isomerization‐driven ring‐opening polymerizations (IROPs) of corresponding thionolactone intermediates. The key to this success relies on the development of a new simple and robust [Et3O]+[B(C6F5)4]− cationic initiator which possesses high activity, exclusive selectivity, living nature, and broad scope of thionolactones. A complete inversion of configuration during IROP of enantiopure γ‐thionovalerolactone is also disclosed, affording isotactic semicrystalline polythioesters (Tm=87.0 °C) with mechanical property compared well to the representative commodity polyolefins. The formation of a highly crystalline supramolecular stereocomplex with enhanced thermal property (Tm=117.6 °C) has also been revealed.