(a)NCA polymerization initiated by LiHMDS or other initiators in THF,initiator i)n-hexylamine,ii)HMDS,iii)bipyNi(COD);(b)LiHMDS-initiated open vessel polymerization of BLGNCA at 26 mg and 2 g scale;(c)GPC traces of po...(a)NCA polymerization initiated by LiHMDS or other initiators in THF,initiator i)n-hexylamine,ii)HMDS,iii)bipyNi(COD);(b)LiHMDS-initiated open vessel polymerization of BLGNCA at 26 mg and 2 g scale;(c)GPC traces of poly-BLG at variable DP;(d)Reaction rates of LiHMDS and hexylamine initiated BLGNCA polymerization in THF with NCA:initiator ratio of 100∶1 and initial NCA concentration at 0.2 mol/L;(e)CD spectra of poly-BLG at variable DP prepared from LiHMDS-initiated NCA polymerization.展开更多
Polyesters,such as polylactide(PLA),are a class of biodegra-dable and biocompatible polymers that have received increasing attention in biomedicine,agriculture,and commodity thermoplastics[1-2].However,the lack of pen...Polyesters,such as polylactide(PLA),are a class of biodegra-dable and biocompatible polymers that have received increasing attention in biomedicine,agriculture,and commodity thermoplastics[1-2].However,the lack of pendant functionality of conventional polyesters makes it difficult to modify and modulate the physicochemical properties in subsequent applications[3-4].Since 2006[5],the ring-opening polymerization(ROP)of O-carbox-yanhydrides(OCAs),which can be readily synthesized from amino acid or hydroxyl acid precursors,has been recognized as a promising route to functionalized polyesters[3-4].However,due to the increased methine C-H acidity,significant racemization of the stereogenic center and decreased stereoregularity have been identified for most OCAs,for instance,ManOCA[6](OCA from mandelic acid)and SerOCA[7](OCA from serine),when using typical 4-(dimethylamino)pyridine(DMAP)as catalyst.To minimize epimerization,some classical metal-based catalysts of coordination polymerization have been introduced to mediate ROP of OCAs,furnishing isotactic polyesters[8].展开更多
文摘(a)NCA polymerization initiated by LiHMDS or other initiators in THF,initiator i)n-hexylamine,ii)HMDS,iii)bipyNi(COD);(b)LiHMDS-initiated open vessel polymerization of BLGNCA at 26 mg and 2 g scale;(c)GPC traces of poly-BLG at variable DP;(d)Reaction rates of LiHMDS and hexylamine initiated BLGNCA polymerization in THF with NCA:initiator ratio of 100∶1 and initial NCA concentration at 0.2 mol/L;(e)CD spectra of poly-BLG at variable DP prepared from LiHMDS-initiated NCA polymerization.
文摘Polyesters,such as polylactide(PLA),are a class of biodegra-dable and biocompatible polymers that have received increasing attention in biomedicine,agriculture,and commodity thermoplastics[1-2].However,the lack of pendant functionality of conventional polyesters makes it difficult to modify and modulate the physicochemical properties in subsequent applications[3-4].Since 2006[5],the ring-opening polymerization(ROP)of O-carbox-yanhydrides(OCAs),which can be readily synthesized from amino acid or hydroxyl acid precursors,has been recognized as a promising route to functionalized polyesters[3-4].However,due to the increased methine C-H acidity,significant racemization of the stereogenic center and decreased stereoregularity have been identified for most OCAs,for instance,ManOCA[6](OCA from mandelic acid)and SerOCA[7](OCA from serine),when using typical 4-(dimethylamino)pyridine(DMAP)as catalyst.To minimize epimerization,some classical metal-based catalysts of coordination polymerization have been introduced to mediate ROP of OCAs,furnishing isotactic polyesters[8].
