the present invention describes the preparation of unimolecular polymeric micelles that bear a hydrophilic shell and a potentially ionizable and relatively hydrophobic core at a determined ph value . the core becomes electrostatically charged as the ph is changed . such micelles can be made from either biodegradable or non - biodegradable polymers . loaded drugs can be physically retained in the micelles when the ph of the surrounding medium favors interactions with the core . upon a change in ph , modification in the ionization state of the core will decrease the interactions between the drug and the inner core and facilitate the release of the micellar contents .