the present invention relates to a pharmaceutical composition of a biologically active agent and a block copolymer composed of a poly forming hydrophilic segment and a polyacrylate - co - acrylic acid ) that is capable of forming supramolecular assemblies or micelles under favourable conditions . the supramolecular assemblies or micelles formed from said polymers associate or dissociate reversibly upon changes in the environmental ph . the pharmaceutical compositions of the present invention contain hydrophobic drugs , cations or polycationic compounds , which can be delivered to the body by oral route or other routes of administration .