H-bonding binary organocatalysis promoted amine-initiated ring-opening polymerizations of lactide from polysarcosine to diblock copolymers. (December 2017)

• Record Type: Journal Article
• Authors: Chen, Siming; Liu, Yaya; Li, Zhenjiang; Wang, Xin; Dong, He; Sun, Herui; Yang, Kun; Gebru, Hailemariam; Guo, Kai
• Is Part Of: European polymer journal. Volume 97(2017)
• Page Start: 389
• Page End: 396
• Publication Date: 2017-12
• Subjects: Diblock copolymer -- H-bonding -- Organocatalysis -- Polylactide -- Sarcosine -- Ring-opening polymerization; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; Polymerization; Polymers; Periodicals; Electronic journals; 547.705
• DOI: 10.1016/j.eurpolymj.2017.10.030
• Languages: English
• ISSNs: 0014-3057

Abstract

Graphical abstract: Highlights: Amine-initiated ROP of LA was in controlled/living manner. Binary H-bonding organocatalysts achieved the ROP of LA under mild conditions. Well-defined PLAs and PSar- b -PLAs with expected molecular weights were prepared. Abstract: Alcohol-initiated ring-opening polymerization (ROP) of cyclic esters for synthesizing polyesters was well established, but amine-initiated ROP of cyclic esters was rare. A challenge is slow initiation and fast propagation in the amine-initiated ROPs. To address the difficulties, an ionic H-bond donor (iHBD) and H-bond acceptor (HBA) binary organocatalysis in amine-initiated ROP of lactide (LA) was developed. Guanidinium hexahydro-2 H -pyrimido[1, 2- a ] pyrimidin-1-ium [(HppH2 ) + ] and tertiary amine sparteine (SP), cooperatively played the role of iHBD/HBA binary catalysts, efficiently promoted ROP of LA from amine initiators toward polylactide (PLA) and polysarcosine- block -polylactide diblock copolymer (PSar- b -PLA). Benzyl amine and N -methylbenzylamine initiated ROPs of LA under mild conditions produced PLAs with predictable molecular weights ( M n, NMR = 2.9–17.1 kg mol −1 ) and narrow dispersities ( Ð M, SEC = 1.13–1.23). Macroinitiator PSar copolymerized with LA under the iHBD/HBA catalysis, producing PSar- b -PLAs with controlled molecular weights ( M n, NMR = 5.7–14.8 kg mol −1 ) and low dispersities ( Ð M, SEC = 1.16–1.21). Kinetics and chain extension experiments confirmed that the amine-initiated ROP of LA in presence of (HppH2 ) + BF4 − /SP was in controlled/living manner. 1 H NMR, 13 C NMR, SEC, and MALDI-ToF MS analyses indicated that the obtained PLA was exclusively initiated from the corresponding amine with amide linkage. An iHBD/HBA binary activation mechanism was proposed.