Surface-initiated catalytic ethylene polymerization within nano-channels of ordered mesoporous silicas for synthesis of hybrid silica composites containing covalently tethered polyethylene

• Published in: Polymer (Guilford) Vol. 52; no. 26; pp. 5961 - 5974
• Main Authors: Xu, Lixin, Ye, Zhibin, Cui, Qingzhou, Gu, Zhiyong, Mercier, Louis
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 13.12.2011; Elsevier
• Subjects: Applied sciences; Catalysts; composite materials; Composites; Covalence; Covalent surface-grafting; electron microscopy; Ethylene; Exact sciences and technology; Forms of application and semi-finished materials; Nanostructure; nitrogen; nuclear magnetic resonance spectroscopy; Ordered mesoporous silica; Palladium; Pd–diimine catalyst; polyethylene; Polyethylenes; Polymer industry, paints, wood; Polymerization; silica; Silicon dioxide; Technology of polymers; thermogravimetry; Covalent surface-grafting; Pd–diimine catalyst; Ordered mesoporous silica; Structure effect; Polyethylene; Surface reaction; In situ; Living polymer; Palladium complex; Complex catalyst polymerization; Experimental study; Reaction rate; Silica; Supported catalyst; Composite material; Pore size; Preparation; Size effect; Porosity; Pd-diimine catalyst; Graft polymers
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2011.11.011

A surface-initiated catalytic ethylene polymerization technique is successfully demonstrated herein for the covalent surface-grafting of polyethylene chains within nanochannels of mesoporous silicas to give hybrid mesoporous silica/polyethylene composite materials. In this technique, a Pd−diimine catalyst, [(ArN C(Me)–(Me)C NAr)Pd(Me)(N CMe)] + SbF 6 − (Ar = 2,6-( iPr) 2C 6H 3) ( 1), was first covalently immobilized onto two ordered mesoporous silicas (SBA-15 and MSU-F) containing surface-bound acryloyl functionalities to render the mesoporous silica-supported chelate Pd−diimine catalysts (Pd-SBA15 and Pd-MSUF, respectively). Surface-initiated ethylene polymerizations within mesopores were subsequently carried out with Pd-SBA15 and Pd-MSUF at an ethylene pressure of 400 psi and 5 °C. A mechanistic study on the polymerization behavior and the confining effects of silica meso-structures on polymer growth has been undertaken. The covalent surface-grafting of polyethylene within silica nanochannels was confirmed by the results from Fourier-transformed infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), nitrogen adsorption–desorption, electron microscopy, and proton nuclear magnetic resonance ( 1H NMR). The content of grafted polyethylene in the composites can be adjusted in a wide range by varying polymerization time. This represents the first report on the covalent surface functionalization of mesoporous silicas with polyethylene via surface-initiated ethylene polymerization. Surface-initiated ethylene polymerization within nanochannels of mesoporous silicas is employed for the synthesis of silica-polyethylene composites with polyethylene chains covalently tethered on silica nanofillers. [Display omitted]