1. Department of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa 3880, South Africa
2. Chemistry Department, University of Dar-es-Salaam, P. O. Box 35091, Dar es Salaam, Tanzania
3. Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
4. Department of Chemistry, Kansas Polymer Research Center, Pittsburg State University, Pittsburg, KS 66762, USA