STAR-SHAPED BLOCK COPOLYMERS - 3. SURFACE AND INTERFACIAL PROPERTIES.

In the reported experiments, surface and interfacial activities of A(B)//2 star-shaped block copolymers, where B is a polyoxirane block and A a polydiene or polyvinyl block, have been measured at 20 degree C. The surface tension of organic solvents is only slightly lowered by these copolymers, whereas a significant surface activity is noted in water. Interfacial tensions are dependent on both the nature of the organic solvent (aliphatic or aromatic hydrocarbons) and the molecular parameters of the copolymers; 50% polyoxirane seems to be the composition of maximum surface activity. The role played by the molecular architecture left bracket A-B or A(B)//2 right bracket of the copolymers is demonstrated. The same limiting interfacial tension is obtained on increasing the concentration of diblock (A-B) or star-shaped block left bracket A(B)//2 right bracket copolymer. The limiting value is, however, attained at significantly lower concentration with the star-shaped copolymers. Their ability to fill the interface is accordingly higher.