EFFECTS OF SURFACE-TENSION ON THE DISLOCATION-STRUCTURES OF DIBLOCK COPOLYMERS

Cross-sectional and plane view TEM, in conjunction with atomic force m icroscopy (AFM), was used to study the dislocations produced within PS -PVP diblock copolymer films. The results showed that islands or holes on the surface of multilayer films were produced by prismatic loop di slocations with a screw component in the layers below the surface. Onl y the contours at the vacuum surface obtained by AFM could be fit with classical elasticity theory. Flattening of the surface by the surface tension when the films were ordered on a silicon substrate induced a large amount of compression in the lamella beneath the surface. In fil ms less than 3/2 lamellar layers thick, this compression is shown to i nduce a transition from lamellar to perpendicular cylinders at the edg e of the island or holes. This transition was suppressed when the dibl ock copolymer molecular weight was decreased or when the films were or dered at a low surface tension interface. A qualitative model which es timates the degree of chain stretching induced by the surface tension is proposed to explain these effects.