Effects of Tacticity on the Formation of Bicontinuous Phases in Diblock Copolymers

The most prominent feature of block copolymers is their ability to self-assemble into ordered structures with periods typically on the scale of 10-100 nm. The symmetry of these ordered structures can depend on a number of factors, including block composition, strength of interactions, conformational asymmetry and tacticity. Tacticity is defined as the order of neighboring dangling groups along a polymer backbone, and influences many properties, ranging from thermal to rheological to conformational. In particular, block copolymers of the same composition with different tacticities could form different microphases. Recent experiments on stereoregular diblock copolymers have also observed the existence of the bicontinuous double-diamond phase, which is not found in neat atactic diblock copolymers. On the other hand, the effects of tacticity on self-assembly is yet to be completely understood. We develop a toy model to incorporate the effects of tacticity within the theoretical framework of self-consistent field theory. We then examine how the formation of bicontinuous phases in diblock copolymers is affected by the inclusion of tacticity effects.