Synthesis and Characterization of α,ω-Dihydroxy Telechelic and Star-Shaped Poly(γ-Butyrolactone)s by Organocatalytic Living/Controlled Ring-Opening Polymerization: Depolymerization and Physical Properties

Abstract

Well-defined poly(γ-butyrolactone) (PγBL) with various topological structures, including linear, α,ω-dihydroxytelechelic, three-arm star, and four-arm star configurations, was successfully synthesized via ring-opening polymerization (ROP) using benzyl alcohol (BnOH), 1,3-propanediol (2OH), 1,1,1-tris(hydroxymethyl)ethane (3OH), and pentaerythritol (4OH) as initiators. The polymerization exhibited living/controlled characteristics under the synergistic catalysis of phosphazene base/1,3-diisopropylthiourea ( ^t Bu-P₄/TU), enabling the synthesis of PγBLs with well-controlled molecular weights and narrow dispersities. Characterization techniques, including ¹H NMR, SEC, and MALDI-ToF MS, confirmed the quantitative incorporation of multifunctional alcohol initiators and validated the resulting chemical structures. Kinetic studies demonstrated that the polymerization rate positively correlates with the number of hydroxyl groups in the initiator; however, due to the relatively poor solubility of 4OH in organic solvents, the reaction initiated by 3OH exhibited the highest polymerization rate. Furthermore, a systematic investigation into the thermal properties and depolymerization behaviors of all synthesized PγBLs highlighted the influence of polymer topology on their characteristics, revealing significant structure–property relationships.