1. Institute of Polymer Chemistry University of Stuttgart Pfaffenwaldring 55 D-70569 Stuttgart Germany
2. Institute of Technical Chemistry University of Stuttgart Pfaffenwaldring 55 D-70569 Stuttgart Germany
3. Institute of Physical Chemistry University of Stuttgart Pfaffenwaldring 55 D-70569 Stuttgart Germany
4. Present address: German Institutes of Textile and Fiber Research (DITF) Denkendorf D-73770 Denkendorf Germany