Control of macromolecular architecture during the reactive functionalization in the melt of olefin polymers

The functionalization of polyolefins is a useful methodology to chemically convert these extremely important commodities into value-added polymers by generating materials with additional properties, such as adhesion, dyeability, paintability, wettability, and compatibility that are not characteristic of the starting macromolecules with a paraffin structure. Owing to the intrinsic chemical resistance and low reactivity of polyolefins, the post-modification processes involve the use of free-radicals and are generally carried out at high temperature, rendering the reactions non-selective. Cross-linking and degradation set boundaries of the desired grafting reaction and their extent of grafting depends on the type of polyolefin and nature/type of chemicals used. The occurrence of these side reactions can severely damage the structure of polyolefins with poor control of ultimate properties. The main purpose here is to describe the conventional process in terms of chemical reactions involved, down to the molecular mechanism, and the dependence on chemicals/reagents nature and amounts. Particular attention is focused on methodologies aimed to hinder side reactions. The corresponding new functionalization approaches are based on well-known process chemistry and are all directed to control the grafting levels and structure/architecture of the initial polymer. Finally, a section is devoted to problems related to the radical post-modification processes of polypropylenes and obtaining new interesting materials by controlling their structure/architecture with the use of specific mono- or poly-functional co-agents as macroradical stabilizers. (C) 2009 Elsevier Ltd. All rights reserved.