Synthesis mechanisms of poly[styrene‐ co ‐(acrylic acid)]‐supported TiCl 4 catalysts modified by magnesium compounds

Soluble poly[styrene‐ co ‐(acrylic acid)] (PSA) modified by magnesium compounds was used to support TiCl 4 . For ethylene polymerization, four catalysts were synthesized, namely PSA/TiCl 4 , PSA/MgCl 2 /TiCl 4 , PSA/( n ‐Bu)MgCl/TiCl 4 , and PSA/( n ‐Bu) 2 Mg/TiCl 4 . The catalysts were characterized by a set of complementary techniques including X‐ray photoelectron spectroscopy, Fourier‐transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, and element analysis. Synthesis mechanisms of polymer‐supported TiCl 4 catalysts were proposed according to their chemical environments and physical structures. The binding energy of Ti 2p in PSA/TiCl 4 was extremely low as TiCl 4 attracted excessive electrons from COOH groups. Furthermore, the chain structure of PSA was destroyed because of intensive reactions taking place in PSA/TiCl 4 . With addition of ( n ‐Bu)MgCl or ( n ‐Bu) 2 Mg, COOH became COOMg‐ which then reacted with TiCl 4 in synthesis of PSA/( n ‐Bu)MgCl/TiCl 4 and PSA/( n ‐Bu) 2 Mg/TiCl 4 . Although MgCl 2 coordinated with COOH first, TiCl 4 would substitute MgCl 2 to coordinate with COOH in PSA/MgCl 2 /TiCl 4 . Due to the different synthesis mechanisms, the four polymer‐supported catalysts correspondingly showed various particle morphologies. Furthermore, the polymer‐supported catalyst activity was enhanced by magnesium compounds in the following order: MgCl 2 > ( n ‐Bu)MgCl > ( n ‐Bu) 2 Mg > no modifier. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012