1. Laboratory for Chemical Surface Science, Department of Chemistry, Physical Chemistry, Royal Institute of Technology, S-100 44 Stockholm, Sweden, and Institute for Surface Chemistry, P.O. Box 5607, S-114 86 Stockholm, Sweden
2. Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, S-221 00 Lund, Sweden
3. Manchester Polymer Centre, Departments of Chemistry and Pharmacy, University of Manchester, Manchester M13 9PL, U.K.