MOLECULAR DESIGN OF MULTICOMPONENT POLYMER SYSTEMS. XII. DIRECT OBSERVATION OF THE LOCATION OF A BLOCK COPOLYMER IN LOW-DENSITY POLYETHYLENE-POLYSTYRENE BLENDS.

A poly(hydrogenated butadiene-b-styrene) (HPB-b-PS) copolymer has been modified by the insertion of a short central polyisoprene (PIP) block. The selective staining of PIP provides an efficient means of locating the block copolymer in the modified LDPE/PS blends by transmission electron microscopy. Transmission electron micrographs of LDPE/PS blends modified by the HPB-b-PIP-b-PS copolymer containing an OsO//4-stained central block have been reported. It is obvious that the block copolymer forms a continuous layer (dark zones) around the dispersed particles of either PS or PE. Futhermore, a more diffuse dark area seems to extend toward PE phases, whereas a part of the copolymer is dispersed in the LDPE phases to the exclusion of the PS ones, whatever the blend composition.