Nanostructured silica materials in olefin polymerisation: From catalytic behaviour to polymer characteristics

This paper reviews progress in organometallic α-olefin polymerisation catalysts supported on zeolites or mesoporous silicas, discussing the role of these nanostructured materials in establishing new catalytic behaviours and polymer properties. Zeolites and other nanostructured materials show unique structural and surface features that have been used with advantage in the immobilisation of a large variety of catalysts, including α-olefin polymerisation catalysts such as metallocene complexes. The characteristics of these materials, such as the ordered porous system, the large surface area and a tuneable acidity have a great impact on the immobilisation of the catalyst, with implication on the formation and nature of active species and polymerisation activity. Methods of preparation, diffusion limitations and confinement effects are rationalised and their role on the catalytic system and final polymer properties is discussed. This review is mainly focused on metallocene catalysts but examples of post-metallocene catalysts and olefin polymerisation behaviour of non-organometallic complexes, covering Ziegler-Natta Ti/V catalysts and Phillips Cr catalysts, as well as metal-modified mesoporous carriers are described and discussed. Additionally, the effects of the nanostructured supports on the morphologies and physical properties of the polyolefins are also covered, and an account is made on how mesoporous materials can be used in the preparation of novel polyolefin nanoblends and nanocomposites.