Block Copolymers of Macrolactones/Small Lactones by a "catalyst-Switch" Organocatalytic Strategy. Thermal Properties and Phase Behavior

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Macromolecules, ISSN: 1520-5835, Vol: 51, Issue: 7, Page: 2428-2436

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Ladelta, Viko; Kim, Joey D.; Bilalis, Panagiotis; Gnanou, Yves; Hadjichristidis, Nikolaos
American Chemical Society (ACS)
Chemistry; Materials Science
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article description
Poly(macrolactones) (PMLs) can be considered as biodegradable alternatives of polyethylene; however, controlling the ring-opening polymerization (ROP) of macrolactone (ML) monomers remains a challenge due to their low ring strain. To overcome this problem, phosphazene (t-BuP), a strong superbase, has to be used as catalyst. Unfortunately, the one-pot sequential block copolymerization of MLs with small lactones (SLs) is impossible since the high basicity of t-BuPpromotes both intra- and intermolecular transesterification reactions, thus leading to random copolymers. By using ROP and the "catalyst-switch" strategy [benzyl alcohol, t-BuP/neutralization with diphenyl phosphate/(t-BuP)], we were able to synthesize different well-defined PML-b-PSL block copolymers (MLs: dodecalactone, ω-pentadecalactone, and ω-hexadecalactone; SLs: δ-valerolactone and ϵ-caprolactone). The thermal properties and the phase behavior of these block copolymers were studied by differential scanning calorimetry and X-ray diffraction spectroscopy. This study shows that the thermal properties and phase behavior of PMLs-b-PSLs are largely influenced by the PMLs block if PMLs components constitute the majority of the block copolymers.