Ethylene oxide-L-lactic acid block copolymer L-Lactic acid-polyethylene glycol block copolymer Oxirane-L-lactic acid block copolymer Oxirane, polymer with (2S)-2-hydroxypropanoic acid, block Polyethylene glycol-L-lactic acid block copolymer Propanoic acid, 2-hydroxy-, (2S)-, polymer with oxirane, block