Colloidal Behaviour of Block Copolymers

Block copolymers .in selective solvent (good solvent for one of the sequences but precipitant for the other ) exhibit the aggregation of molecules through a closed association process in analogy to conventional surface active agents. Such an aggragation of molecules in to 'micelles' is owing to the presepce of two incompatible sequences which behave differently in selective solvent. The copolymer micelle is built up of the core of the insoluble block surrounded by the fringes of the soluble block, beingtof the order of several nanometer in size. In most cases such micelles are spherical in shape. The micellar parameters l critical micelle concentration, agregation number, micellar weight, shape and internal structure of micelle) largely depend upon the molecular characteristics of the micelle forming block.copolymer (molecular mass, relative composition of the blocks and structure), selectivity of the solvent and temperature.