Synthesis and characterization of PCL/PEG/PCL triblock copolymers by using calcium catalyst

• Published in: Polymer (Guilford) Vol. 44; no. 7; pp. 2025 - 2031
• Main Authors: Piao, Longhai, Dai, Zhongli, Deng, Mingxiao, Chen, Xuesi, Jing, Xiabin
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.03.2003; Elsevier
• Subjects: Applied sciences; Calcium catalyst; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Poly(ε-caprolactone); Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Triblock copolymer; Poly(ε-caprolactone); Triblock copolymer; Calcium catalyst; Ring opening polymerization; Calcium complex; Catalytic reaction; Ammino complex; Ethylene oxide copolymer; Experimental study; Caprolactone copolymer; Solution structure; Preparation; Poly(e-caprolactone); Aqueous solution; Micellar solution; Aliphatic copolymer; Amphiphilic polymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(03)00087-9

Triblock copolymer PCL–PEG–PCL was prepared by ring-opening polymerization of ε-caprolactone (CL) in the presence of poly(ethylene glycol) catalyzed by calcium ammoniate at 60 °C in xylene solution. The copolymer composition and triblock structure were confirmed by 1H NMR and 13C NMR measurements. The differential scanning calorimetry and wide-angle X-ray diffraction analyses revealed the micro-domain structure in the copolymer. The melting temperature T m and crystallization temperature T c of the PEG domain were influenced by the relative length of the PCL blocks. This was caused by the strong covalent interconnection between the two domains. Aqueous micelles were prepared from the triblock copolymer. The critical micelle concentration was determined to be 0.4–1.2 mg/l by fluorescence technique using pyrene as probe, depending on the length of PCL blocks, and lower than that of corresponding PCL–PEG diblock copolymers. The 1H NMR spectrum of the micelles in D 2O demonstrated only the –CH 2CH 2O– signal and thus confirmed the PCL-core/PEG-shell structure of the micelles.