1. Contribution from the School of Biological and Chemical Sciences, Birkbeck College, University of London, Gordon House, 29 Gordon Square, London WC1H 0PP, United Kingdom, Institute of Polymer Chemistry, Polish Academy of Sciences, 34 M. Curie-Sklodowskiej, St., 41-800 Zabrze, Poland, and Institute of Chemistry and Environmental Protection, Pedagogical University, 42-201 Czestochowa, Poland