1. Chemistry Department, Faculty of Science and Engineering, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, U. K.
2. Faculty of Science, North East Wales Institute of Higher Education, Mold Road, Plas Coch, Wrexham, Clwyd L11 2AW, U. K.
3. Instituto de Ciencia y Technologia de Polímeros, C. S. I. C., c/Juan de la Cierva 3, 28006 Madrid, Spain