Poly(ethylene glycol)-block-poly(γ-benzyl l-glutamate)-graft-poly(ethylene glycol) (PEG-b-PBLG-g-PEG) copolymer was synthesised by the ester exchange reaction of PEG-block-PBLG copolymer with mPEG. The self-association behaviour of PEG-b-PBLG-g-PEG in mixtures of ethanol, chloroform, and trifluoroacetic acid as denaturing acid was investigated by transmission electron microscopy, nuclear magnetic resonance spectroscopy, FT-IR spectroscopy, dynamic light scattering, and viscometry. It was revealed that the increase in denaturing acid content in the mixed system not only promoted the critical micelle concentration but also changed the morphology of the polymeric micelles from elliptical to spherical.