Diblock copolymer ultrathin films studied by high resolution electron energy loss spectroscopy

Surface segregation of polymers forming thin films is relevant in several i ndustrial applications. This paper studies the influence of preparation par ameters on the surface composition of poly(ethylene oxide)-polystyrene dibl ock copolymer ultrathin films. Silicon wafers were used as substrates. The film preparation method (spin coating vs. casting followed by solvent evapo ration), solvent (THF vs. CCl4), annealing vs. non-annealing and the substr ate nature (native silicon oxide vs. silanized substrate) were analyzed. Hi gh resolution electron energy spectroscopy in vibrational energy loss range was used to estimate the extreme surface composition. Generally, THF favor s the surface segregation of polystyrene. After annealing, whatever the pre paration method, the polystyrene preferentially segregates at the surface w ithout forming a pure overlayer. These results were compared with the surfa ce compositions calculated from X-ray photoelectron spectroscopy spectra of the films. (C) 2001 Elsevier Science B.V. All rights reserved.