Controlled preparation of polyethylene glycol and PolyMactide block copolymers in the presence of a monomer activator

The first approach to synthesis of polyethylene glycol (PEG) and poly L-lactic acid (PLLA) block copolymers through an active ring opening polymerization (ROP) of L-lactic acid (LA) by PEG in the presence of CF ₃SO₃H, was investigated. Molecular weights distributions of PEG, and PEG and PLLA block polymers were measured by a Futects At 3000 GPC system using three columns at 40°C, using CHC13 as an eluent with a flow rate of 0.8 mL/min by polystyrene calibration. All glasses were dried by heating in vacuum and handled under a dry nitrogen stream. The MPEG solution was distillated by azeotropic distillation to remove water. After 24 h, the reaction mixture was treated with alumina to neutralize the acid and was poured into ethyl ether to precipitate a polymer, which was separated from the supernatant by decantation. Colorless diblock copolymers were obtained in near quantitative yields after ether precipitation. Characteristic PLLA and PEG block copolymer peaks were observed in ¹H NMR spectrum.