Stereoselective Ring‐Opening Polymerization of Racemic Lactide by Racemic Organo‐Catalyst at Room Temperature: Direct Access to Stereocomplex Polylactides

Abstract

AbstractThe stereoregularity of poly(lactide) (PLA) plays a significant role in its physicochemical properties. In recent years, various metallic and nonmetallic catalysts have been developed. Organic catalysts, in particular, have garnered attention due to their potential use in biomedical applications, making them safer options. This study presents the design of a cost‐effective thiourea‐based racemic organocatalyst [(rac‐TU)Me] and its effective utilization in ring‐opening polymerization (ROP) of lactide. Using the catalyst and optimized base (N,N‐dimethylcyclohexylamine), ROP in dichloromethane achieved 98% monomer conversion and controlled molecular weights in 48 h. The polylactides obtained using this catalyst exhibited moderate tacticity, with a Pm value ranging from 0.71 to 0.78. The bulk structure of synthesized poly(lactic acid) (PLAs) is extensively studied using DSC, FTIR, and WAXS. The DSC analysis indicated stereoregular PLAs synthesized from rac‐lactide exhibited a higher melting transition than isotactic PLAs. Furthermore, the FTIR and WAXS studies revealed characteristic peaks and patterns typically associated with stereocomplex PLAs. These analytical results confirm the stereocomplex bulk structures of these PLAs synthesized using this organic catalyst [(rac‐TU)Me].