Surface And Bulk Phase Separations In Block Copolymers And Their Blends PDF Download

The phase transition and phase separation behavior occurring in mixtures containing an A-B block copolymer and an A homopolymer is discussed. With a pure block copolymer an order-disorder transition can be induced by raising the temperature, whereby the ordered lattice of segregated microdomains becomes unstable and give way to a homogeneous liquid structure. Small amounts of a homopolymer added to a block copolymer can be accomodated in the microdomains consisting of the same type of monomeric units, up to a solubility limit that depends on the relative length of the homopolymer and the compolymer block and on the temperature. The order-disorder transition temperature of the block copolymer is also affected by the added homopolymer. At the other extreme of concentration, spherical micelles of block compolymer is formed when a small amount of the copolymer is formed when a small amount of the compolymer is added in the bulk homopolymer, and its critical micelle concentration again depends on the relative length of the molecules and block involved and on the temperature. Measurements were made with light scattering and small-angle X-ray scattering techniques to determine the phase behavior of mixtures containing a styrene-butadiene block copolymer and either a polystyrene or a polybutadiene.