Stereoselective Ring-Opening Polymerization of Lactones with a Fused Ring Leading to Semicrystalline Polyesters

Monomer design is vital in the development of polymers with desired thermal and mechanical properties. Here, we prepared two monomers (M1, trans-octahydro-2H-benzo[b][1,4]dioxepin-2-one and M2, trans-octahydro-2H-benzo[b][1,4]-oxathiepin-2-one) based on 1,5-dioxepan-2-one (DXO) and 1,4-oxathiepan-7-one (OTO) by incorporating trans-fused cyclohexyl rings. These monomers featured living ring-opening polymerization-yielding polymers with predictable molecular weights while maintaining low D. values. To gain a better understanding of the influence of polymer tacticity on polymer properties, a series of polymers with variable tacticities were prepared under various conditions. Their thermal property studies revealed that increasing the P-r value to 91% of P(M2) led to an emerging melting-transition temperature of 101 degrees C. Copolymerization of M1 and M2 allowed us to obtain a well-defined diblock polymer P(M2)-b-P(M1) and random copolymer P(M1-co-M2) with distinct thermal behaviors. Excitingly, oxidation of P(M2) resulted in an increase of the glass transition temperature from 18 to 112 degrees C. Hydrolysis of these polymers to corresponding hydroxyl acids and subsequent lactonization reactions enabled a closed-loop life cycle of P(M)s.

Automated summary

This article discusses the importance of monomer design in developing polymers with desired properties and investigates the impact of polymer tacticity on properties. Various monomers were prepared and polymerized to study their thermal behaviors.