Determination of the individual block lengths of the block copolymers of Poly(trimethylene carbonate) by liquid chromatography at critical conditions

Abstract

Amphiphilic block copolymers based on poly(trimethylene carbonate) (PTMC) have gained significant attention for biomedical applications owing to their unique degradation characteristics. Ring-opening polymerization (ROP) is the most widely employed method for polymerization of cyclic carbonates, especially for trimethylene carbonate (TMC). Herein, di- and tri-block copolymers of PTMC are synthesized by ROP of TMC using poly(ethylene glycol) monomethyl ether (MeO-PEG) or poly(ethylene glycol) (PEG) as a macro-initiator, respectively. The synthesized products are characterized by size-exclusion chromatography (SEC) and nuclear magnetic resonance spectroscopy (1H NMR) for their molar mass and chemical composition, respectively. However, these techniques are inconclusive about several pertinent aspects of the block copolymers, such as individual block length and unwanted homopolymer content. To address these limitations, liquid chromatography at critical conditions of both PEG and PTMC are employed. Chromatographic critical conditions for PTMC are reported for the first time in the current study. The analysis protocol successfully reveals the individual block lengths of both blocks of the block copolymers, along with the quantification of the unwanted homopolymers in the samples. The individual block lengths and the presence of homopolymers significantly affect the self-assembly capability and drug-loading capacity of amphiphilic block copolymers. Thus, the study divulges important information crucial for the development of structure-property correlations, which is essential for optimizing the performance of these block copolymers in biomedical applications.