Abstract
Deuterium labeling of semi‐crystalline polymers can dramatically affect their crystallization behaviors. However, the influence of different labeled positions in a partially deuterated polymer on its crystallization is still far from understood. Here, we synthesized a series of selectively deuterated poly(ε‐caprolactones) (PCLs) through ring‐opening polymerization of ε‐caprolactone with controlled deuteration sites, including fully protiated (D0), fully deuterated (D10), tetra deuteration at the 3‐ and 7‐ caprolactone ring positions (D4) and hexa deuteration at the 4‐, 5‐, and 6‐ caprolactone ring positions (D6). All the PCLs showed a similar lamellar structure and parameters. Differential scanning calorimetry (DSC) analysis revealed that the equilibrium melting temperature 𝑇0𝑚, melting temperature Tm, crystallization temperature Tc, and crystallization kinetics changed systemically with the deuterium content except for D4, which indicates that the presence of CD2 moieties on either side of ester group in the polymer chain combined with isotopic inhomogeneity could influence the chain packing. The nonmonotonic trend of Tm as a function of deuterium content could be attributed to the difference in a hydrogen‐bond like intermolecular interaction between different PCLs. Partially deuterated PCLs (D4 and D6) showed an Avrami index near 2. After analyzing the parameters at the same supercooling temperature ΔTc, the existence of two crystallization regimes of PCLs were detected.
