Synthesis and characterization of uniform OCL-OEG block cooligomers

Abstract

Block copolymers are an interesting class of materials, offering the opportunity to form nanostructured morphologies, making them suitable for a broad range of applications in nanotechnology, medicine, or biotechnology. Especially for the pharmaceutical sector, a uniform structure and a distinct structure–property relationship is desirable to manufacture highly reproducible and tailor-made materials. Herein, we report the synthesis and characterization of uniform (Đ = 1.01) oligo(ε-caprolactone)-oligo(ethylene glycol) (OCL-OEG) block co-oligomers (BCOs). Three different BCOs, varying in the length of the hydrophobic caprolactone segment, were obtained via Steglich esterification of the corresponding homo oligomers. A clear dispersity and composition dependent structure–property relationship based on the thermal properties is observed, compared to identical structures similar in M_n and dispersities of Đ = 1.06, obtained via ring-opening polymerization (ROP) of ε-caprolactone. In addition, increased long-range-order distances L₀ with increasing dispersity of the BCOs are found for the formed morphologies after solvent vapor annealing (SVA). These results highlight the importance of uniform structures for a better understanding of the structure–property relationship of block copolymers.