Catenated Poly(∈-caprolactone) and Poly(l -lactide) via Ring-Expansion Strategy

Catenated poly(∈-caprolatone) (PCL) and poly(l-lactide) (PLA) were synthesized by a ring-expansion strategy based on a catenated tin initiator. Catenated PCLs with different degrees of polymerization (DP_n) were obtained by modifying the feed ratios of monomer to initiator, and subsequent decomplexation rendered the copper-free catenated PCL. Both the Cu(I)-templated catenated PCL and Cu(I)-free catenated PCL were characterized by UV-vis, ¹H NMR, FT-IR, and GPC analyses. The comparative GPC analyses of catenated polymers and their linear analogues were also performed, which revealed a reduced hydrodynamic diameter for the catenated polymers. The crystallinity of the catenated PCL compared to that of linear PCL was also studied by DSC and WAXS, and the Cu(I)-free catenated PCL exhibited a lower degree of crystallinity but larger crystallite size.