New architecture of supported metallocene catalysts for alkene polymerization

• Published in: Journal of polymer science. Part A, Polymer chemistry Polymer chemistry, 2007-12, Vol.45 (23), p.5480-5486
• Main Authors: Velilla, Teresa, Delgado, Katherine, Quijada, Raúl, Bianchini, Daniela, Barrera Galland, Griselda, Dos Santos, João Henrique Z, Fasce, Diana P, Williams, Roberto J.J
• Format: Article
• Language: English
• Subjects: Applied sciences; catalytic activity; ethylene polymerization; Exact sciences and technology; Inorganic and organomineral polymers; metallocene catalysts; Organic polymers; Physicochemistry of polymers; polyethylene; Polymerization; Preparation; Preparation, kinetics, thermodynamics, mechanism and catalysts; soluble functionalized silica; supported metallocene catalysts; supports
• ISSN: 0887-624X; 1099-0518
• DOI: 10.1002/pola.22292

We report the synthesis of a supported metallocene catalyst that exhibits the same activity as a homogeneous catalyst for ethylene polymerization reactions. The key to this new catalytic system is a hybrid organic-inorganic polymer obtained by the cocondensation of an organotrialkoxysilane (OTAS; 40 mol %) with tetraethoxysilane (TEOS; 60 mol %). The particular organic group of OTAS enabled us to avoid gelation when the hydrolytic condensation was performed with a thermal cycle attaining 150 °C. The resulting product [soluble functionalized silica (SFS)] was a glass at room temperature that was soluble in several organic solvents such as tetrahydrofuran and toluene. The ²⁹Si NMR spectrum of SFS showed that the OTAS units were fully condensed (T₃ species), whereas the TEOS units were mainly present as tricondensed (Q₃) and tetracondensed (Q₄) units. SFS was grafted onto activated silica through a reaction of silanol groups. The metallocene [(nBuCp)₂ZrCl₂] was covalently bonded to the SFS-modified support. The polymerization of ethylene was carried out in toluene in the presence of methylaluminoxane. The activity of the supported catalyst was similar to that of the metallocene catalyst in solution. The simplest explanation accounting for this fact is that most of the metallocene was grafted to SFS species issuing from the surface of the support through a reaction with their silanol groups. This improved the accessibility of the monomer to the reaction sites. Specific interactions of the metallocene species with neighboring organic branches of SFS might also affect the catalytic activity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5480-5486, 2007