Randomly Functionalized Polyethylenes: In Quest of Avoiding Catalyst Deactivation

Well-defined randomly functionalized polyolefins produced by catalysis form an interesting class of polymers with great potential for various applications. One of the major challenges for the production of these materials forms the incompatibility of the commonly used electrophilic group 4 metal based catalysts and the desired nucleophilic, especially protic functionalities like hydroxyl and carboxylic acid groups. Although pacification of the protic functionality remains necessary, it was found that lowering the oxidation state of a constrained geometry type of catalyst from Ti(IV) to Ti(III) turned the catalyst unexpectedly tolerant to a wide variety of aluminum alkyl pacified, hydroxyl-functionalized olefin comonomers. The catalyst's tendency to undergo chain transfer to aluminum, which was found to be intensified by the presence of aluminum alkyl pacified, hydroxyl-functionalized comonomers, can be efficiently suppressed by the addition of a sterically hindered phenol such as 2,6-bis(1,1-dimethylethyl)-4-methylphenol (BHT). Surprisingly, the addition of BHT also increases the catalyst's affinity to incorporate these functionalized comonomers.