New architecture of supported metallocene catalysts for alkene polymerization

Abstract

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

Polyethylene Nanocomposites Obtained by in situ Polymerization via a Metallocene Catalyst Supported on Silica Nanospheres

“…Metallocene catalysts have became an important class of catalysts for olefin polymerization, due to the combination of high activities with excellent stereoregularity for α‐olefins 1–3. Furthermore, metallocene catalysts produce polymers with a narrow molecular weight distribution and allow the incorporation of comonomers with specific sequences for polyethylene (PE) and poly(propylene) (PP) and in the case of α‐olefins, the isotacticity and number of misinsertions can be controlled 3, 4.…”

“…The main purpose of this work is to evaluate two alternatives for preparing heterogeneous catalyst systems and to carry out the synthesis of the PE nanocomposites, in order to check the best way to obtaining high activities, good dispersion of the nanofiller, and improving of the particle polymer morphology. The metallocene catalyst, bis( n ‐butylcyclopentadienyl) zirconium dichloride (( n BuCp) 2 ZrCl 2 ) (Aldrich) was used because this catalyst has a high catalytic activity for ethylene polymerization 2, 15. Two supported systems were prepared; in the first system the catalyst was supported directly on the SN (Cat/SN) while in the second system the catalyst was supported on SN which were pretreated with MAO (Cat/MAO/SN).…”

Novel antimicrobial polyethylene composites prepared by metallocenic in situ polymerization with TiO2‐based nanoparticles

“…INTRODUCTION Tailor-made polyethylene (PE) with narrow molecular weight distribution can be obtained using metallocene catalysts through a highly active polymerization process, allowing the synthesis of novel materials with specific properties. 1,2 To further extend the range of PE applications, different types of nanoparticles such as modified clay, 3 SiO 2 , 4 and ZrO 2 5 have been incorporated, improving some final properties of the nanocomposite produced, such as mechanical, barrier, and thermal. There are three main conventional methods to produce PE nanocomposites 5,6 : (i) melt compounding, (ii) solution blending, and (iii) in situ polymerization.…”

Metallocene supported on a polyhedral oligomeric silsesquioxane‐modified silica: Structural characterization and catalytic activity for ethylene polymerization

“…The aim of our research group is to describe the use and interactions of different spacers between a silica matrix and a conventional metallocene precatalyst such as ( n ‐BuCp) 2 ZrCl 2 . In a previous article, the metallocene precatalyst was supported on soluble functionalized silica (SFS) and on SFS‐modified silica 15. Excellent results were obtained with these catalytic systems.…”