Surface morphology of PS-PDMS diblock copolymer films

Spin coated thin films (similar to 400 Angstrom) of poly(styrene)- poly (dimethylsiloxane) (PS-PDMS) diblock copolymers have been investigated using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy. Surface segregation of the poly(dimethylsiloxane) blocks was studied for five diblock copolymers which ranged in molecular weight from 7 kg/mol to 500 kg/mol. The films were annealed above and below the highest glass transition temperature of the two polymer blocks but below the order-disorder transition temperature. Information concerning the chemical in-depth distribution of the films was extracted by use of peak shape analysis of the X-ray Photoelectron Spectra via the Tougaard Method. The amount of dimethylsiloxane in the uppermost part of the films was quantified as a function of annealing time and temperature. For annealing above the PS glass transition temperature, surface segregation of the dimethylsiloxane chain-ends occurs for all the studied PS-PDMS diblock copolymers. At room temperature, surface segregation takes place only when the amount of dimethylsiloxane in the diblock copolymers is small. (C) 2001 Elsevier Science B.V. All rights reserved.