1. a Department of Polymer Science , National Research Center , Dokki, Giza , Egypt
2. b Department of Chemistry , The University of Akron , Akron , OH , 44325-4717 , USA
3. d The Maurice Morton Institute for Polymer Science, The University of Akron , Akron , OH , 4325-4717 , USA
4. c Department of Polymer Science , University of Akron , Akron , OH , 44325-4717 , USA