Angela Mohanty - Transition Metal-Catalyzed Functionalization of Polyolefins Containing C-C, C=C, and C-H Bonds

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Mohanty, A.D. and Bae, C., Transition Metal-Catalyzed Functionalization of Polyolefins Containing C–C, C=C, and C–H bonds, in Advances in Organometallic Chemistry, editor: Pedro J. Perez, Vol. 64, ADOMC, UK: Academic Press, 2015, pp. 1-39


  Polyolefins are prepared from vinyl monomers via free radical,

  anionic, cationic, and metal-catalyzed coordination   polymerization processes.

  In this review article, we divide them into two classes: (i)   saturated


  polyolefins, such as polyethylene (PE) and polypropylene (PP)   and (ii) unsaturated polyolefins, such as polybutadiene   (PBD), polystyrene (PS),

  and styrene-based copolymers. Regardless of whether they are   saturated or

  unsaturated, polyolefins are the most widely used commodity   materials

  because they have robust physical and mechanical properties and   use inexpensive

  feedstocks. Because polyolefins are made of only nonpolar   covalent

  bonds—primarily C-C, C=C (for unsaturated polyolefins), and C-H—

  they lack good surface adhesion properties and are seldom used   with other

  organic and inorganic materials.1  This disadvantage has thus far limited

  broader applications of polyolefins. Certain polyolefins,   particularly unsaturated

  ones, can be obtained as copolymers (e.g., copolymers of   styrene).

  However, the range of vinyl monomers that readily undergo   polymerization

  and the diversity of functional groups that can be incorporated   are often limited.

  Additionally, the copolymerization approach often yields polymers

  with insufficient molecular weight that cannot be used   commercially.  The chemical modification of polyolefins via   selective and controlled

  functionalization offers an alternative approach for the   incorporation of

  polar functionality to inherently nonpolar materials and changing   their specific

  properties. Traditional chemical modifications use free radical   and electrophilic

  addition/substitution reactions for saturated and unsaturated

  polyolefins, respectively. However, those reactions, which   involve highly

  reactive intermediates (i.e., free radicals and carbocations),   are generally difficult

  to control and are therefore accompanied with undesired side   reactions

  such as polymer chain scission and cross-linking. Because the   physical properties

  of polymer materials depend heavily on molecular weight and the

  extent of polymer chain entanglement, any deleterious side   reactions that

  negatively affect the molecular weights of functionalized   polymers sacrifice

  physical properties and should be avoided.  During recent   decades, transition metal complexes have been central in

  the catalysis of many new and existing organic reactions. Some of   these complexes

  have been successfully adopted for polymer functionalization. In   this

  review article, we summarize the recent progress of polyolefin   functionalization

  catalyzed by transition metal complexes. The sections are   conveniently

  divided according to polyolefin structure. We discuss

  modifications of polyolefins containing (i) alkene CdH bonds   such as those

  in PBD, (ii) aromatic CdH bonds   such as those in PS, and (iii) saturated

  CdC and   CdH bonds   such as those in PE. A number of excellent review

  articles and books have extensively discussed the chemical   modifications of

  polymers including polyolefins.2–9  Thus, this review primarily emphasizes

  catalytic polymer functionalization processes developed since the   late 1990s.

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