Sub-10 nm Nano-Organization in AB2- and AB3‑Type Miktoarm Star Copolymers Consisting of Maltoheptaose and Polycaprolactone

• Published in: Macromolecules Vol. 46; no. 4; pp. 1461 - 1469
• Main Authors: Isono, Takuya, Otsuka, Issei, Kondo, Yohei, Halila, Sami, Fort, Sébastien, Rochas, Cyrille, Satoh, Toshifumi, Borsali, Redouane, Kakuchi, Toyoji
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 26-02-2013
• Subjects: Applied sciences; Exact sciences and technology; Natural polymers; Physicochemistry of polymers; Starch and polysaccharides; Ring opening polymerization; 1,3-Dipolar cycloaddition; Organic azide; Oligosaccharide; Temperature effect; Nanostructure; Experimental study; Chemical coupling; Star copolymer; Monodispersed polymer; Caprolactone copolymer; Domain structure; Preparation; Oside polymer; Polycaprolactone; Block copolymer
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma3026578

The AB2- and AB3-type miktoarm star copolymers consisting of maltoheptaose (MH, as A block) and poly(ε-caprolactone) (PCL, as B block), namely MH-b-(PCL)2 and MH-b-(PCL)3, were synthesized, and their nano-organization was characterized. The syntheses of MH-b-(PCL)2 and MH-b-(PCL)3 were carried out through two reaction steps: (1) preparation of linear and three-branched PCLs bearing an azido group on the chain center (N3-(PCL)2 and N3-(PCL)3) by the diphenyl phosphate-catalyzed ring-opening polymerization of ε-caprolactone (ε-CL) using azido-functionalized di- and triols (N3-(OH)2 and N3-(OH)3) as the initiators and (2) the copper-catalyzed azide–alkyne cycloaddition of N3-(PCL)2 and N3-(PCL)3 with the ethynyl-functionalized MH. The miktoarm star copolymers having M n for the PCL block of ca. 5000 (MH-b-(PCL2.5k)2 and MH-b-(PCL1.7k)3) and 10 000 (MH-b-(PCL5k)2 and MH-b-(PCL3.3k)3) were obtained with a very narrow polydispersity index of less than 1.05. Bulk samples of the four types of miktoarm star copolymers exhibited body-centered cubic phases, as determined by small-angle X-ray diffraction experiments. The domain-spacing were determined to be 9.8 nm for MH-b-(PCL2.5k)2, 8.8 nm for MH-b-(PCL1.7k)3, 10.5 nm for MH-b-(PCL5k)2, and 9.8 nm for MH-b-(PCL3.3k)3, which were smaller than those of the corresponding linear diblock copolymers.