ON THE INTERFACIAL WIDTH IN TRIBLOCK VERSUS DIBLOCK COPOLYMERS - A NEUTRON REFLECTIVITY INVESTIGATION

The relationship between the interfacial width in a lamellar triblock copolymer and that in the respective lamellar diblock has been investi gated by neutron reflectivity, taking advantage of the surface-induced orientation of the domains parallel to the free surface in thin copol ymer films. The effective interfacial width in a nyl-2-pyridine)-polys tyrene-poly(vinyl-2-pyridine) triblock is found to be similar to 38% n arrower than that for the respective diblock. This difference is discu ssed in relation to theoretical predictions and is tentatively attribu ted to a reduced contribution of the thermal fluctuations of the conce ntration profiles to the effective interfacial width because of the pr esence of the mid-block bridges connecting the end-block domains in th e triblock lamellae.