The present invention provides a method for making a composition comprising an amphiphilic polymeric material which comprises a straight or branched chain carbon-carbon backbone and a multiplicity of side chains attached to the backbone wherein in the method, backbone precursors comprising acylating groups are mixed with side chain precursors which comprise a nucleophilic group at at least one terminus, to form a reaction mixture the backbone precursors, side chain precursors and/or the reaction mixture are heated the reaction mixture is stirred and the nucleophilic groups react with the acylating groups to form the amphilphilic polymeric material wherein the side chains are linked to the backbone via acyl linkages characterised in that the reaction mixture does not comprise organic solvent.
