Synthesis of poly(-lactide-co-5-amino-5-methyl-1,3-dioxan-2-ones)[P(L-LA-co-TAc)] containing amino groups via organocatalysis and post-polymerization functionalization

Abstract

Abstract Poly( l -lactide-co-5-benzyloxycarbonylamino-5-methyl-1,3-dioxan-2-ones) (P(L-LA-co-TMAc)) containing amino groups were synthesized by the ring-opening polymerization of l -lactide(L-LA) and 5-benzyloxycarbonylamino-5-methyl-1,3-dioxan-2-one (TMAc), which was catalysed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in solution or 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in bulk. Followed by deprotection under acidic conditions, deprotected copolymer poly( l -lactide-co-5-amino-5-methyl-1,3-dioxan-2-ones)[P(L-LA-co-TAc)] was prepared. Compared to polymerization reactions catalysed by stannous octoate (Sn(Oct)2), a metallic catalyst, organocatalysts showed precise control over the composition and polydispersity index of the copolymers. Proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) analyses confirmed the polymeric structure and sequence distribution of the product, which indicated that L-LA and TMAc formed random copolymers. Relatively longer PLLA segments were incorporated into the copolymer during the initial polymerization period due to differences in the reactivity of the two monomers, especially in the DBU-catalysed system. And copolymers with gradient property were obtained. The amino bearing deprotected copolymers served as macro-initiator of the subsequent ROP of benzyl- l -glutamate-N-carboxyanhydride(BLG-NCA). Finally, the multi-composite graft copolymer P(L-LA-co-TAc)-g-PBLG was obtained through post-polymerization functionalization.