USING SURFACE-ACTIVE RANDOM COPOLYMERS TO CONTROL THE DOMAIN ORIENTATION IN DIBLOCK COPOLYMER THIN-FILMS

The structure of thin films of a symmetric diblock copolymer, P(dS-b-M MA) (dS = perdeuterated styrene, MMA = methyl methacrylate), was inves tigated near preferential and nonpreferential (neutral) surfaces. Neut ral surfaces were achieved at the substrate and air interfaces by loca lizing random copolymer, P(S-r-MMA), having a styrene fraction of 0.60 , to each of these interfaces. This was performed by chemically grafti ng the random copolymer to the substrate and anchoring a surface activ e random copolymer having a perfluorinated end group to the air interf ace, respectively. Neutron reflectivity and small-angle neutron scatte ring were used to determine the orientation of the lamellar microdomai ns for films having various boundary conditions. Successive steps of C F4 reactive ion etching followed by field emission scanning electron m icroscopy were used to ascertain the orientation of the microdomains a s a function of film depth. For films confined between two continuous neutral surfaces, the orientation of the lamellar microdomains is obse rved to be perpendicular to the film surfaces throughout the entire fi lm thickness.