Functionalization of polyolefins

Until recently, maleic anhydride has been used mostly for the functionalization of polyolefins due to the high reactivity of the anhydride group toward sucessive... 

The regiospecific functionalization of polyolefins can be achieved in a similar fashion to yield organoboranes, which are then converted into alcohols (Equation (21)).32... 

The rhodium-catalyzed borylation of alkanes is applied to regiospecific functionalization of polyolefines.165,165a The reaction of polypropylenes (atactic, isotactic, and syndiotactic) with B2pin2 in the presence of Cp Rh( 74-C6Me6) catalyst at 200 °G affords the borylated polymers, which are treated with basic hydrogen peroxide in a mixture of THF and H20 to oxidize the boronate esters to the corresponding alcohols (Scheme 20). The hydroxylated polymers contain 0.2-1.5% hydroxymethyl side-chains. 

Alkane dehydrogenation has been demonstrated as a suitable method for the functionalization of polyolefins such as atactic poly(l-hexene) under homogeneous conditions (Equation 12.6) [23]. 

Another possibility in the functionalization of polyolefins results from the copolymerization of olefins with boran monomers. Chung and Rhubrigut... 

Chauhan BPS, Balagam B. (2006) SUyl Functionalization of Polyolefines. Macromolecules 39 2010-2012. 

Initial reports on the borylation of alkanes using isolated transition-metal-boryl complexes date back to 1995, when Hartwig showed that Cp Re(CO)2(Bpin)2 converts pentane to 1-borylpentane with high regioselectivity. " The catalytic C-H borylation of alkanes with Cp Re(CO)3 using photochemical activation was demonstrated soon thereafter (equation 25). Also, an efficient thermal process that involves the use of rhodium catalysts has since been developed (equation 26). It is interesting to note that this methodology is not restricted to small molecules, but has recently been exploited for the direct side-chain functionalization of polyolefins. ... 

The tunable metallocene catalyst with a well-defined polymerization mechanism provides distinctive advantages in the preparation of new polymers with well-controlled molecular structures, especially functional polyolefins that are very difficult to prepare by other methods. Since the discovery of HDPE and i-PP about half a century ago, functionalization of polyolefin has been a scientifically challenging and industrially important area. The constant interest, despite lack of effective functionalization chemistry, is due to the strong desire to improve polyolefin s poor interactive properties. The hydrophobicity and low surface energy of polyolefin has limited its applications, especially in the areas of coating, blends, and composites, in which adhesion, comparability, dispersion, and paintability are paramount. 

Chung, T.C. Functionalization of Polyolefins, Academic Press London, 2002. 

Dias et al,35 reported that high-quality poly aniline can be prepared catalytically in MeCN using aniline, HC1, H2O2, and the copper catalyst [CuCl(MeTpMs)]. Controlled, copper-catalyzed functionalization of polyolefins by using [Cu(Tpx)L] (L = MeCN) complexes has been reported by Perez and coworkers.36... 

Graft-functionalization of polyolefin in a separate processing step e.g., polyethylene-g-maleic anhydride, polypropylene-g-maleic anhydride). 

The third trend is the growing interest in functionalization of polyolefin blends in their melt by means of reactive extrusion. Particular attention has been paid to blended systems PP/PE, PP/EPR, PE/ethylene-octene copolymer (EOC), PP/EOC, PE/PS, and PP/PS functionalized in melt by reactive extrusion. The major field for application of functionalized polyolefin blends is compatibilization of blends of condensation polymers, where they can be used in place of homopolyolefins. 

F. Ciardelli, M. Aglietto, M. B. Coltelli, E. Passaglia, G. Ruggeri, and S. Coiai, Functionalization of polyolefins in the melt, in Modification and Blending of Synthetic and Natural Chains, F. Ciardelli and S. Penezek (eds.), Kluwer Academic Publishers, Dordrecht, 2003, Chapter 4. 

Despite the commercial success of polyolefins, the lack of reactive groups in the polymer structure has limited some of their applications, particularly where adhesion, dyeability, or compatibility with other functional polymers is paramount. The functionalization of polyolefins has long been not only of industrial importance but also a scientific challenge. Unfortunately, both direct polymerization and postmodification processes toward the functionalization of polyolefins have suffered... 

A Novel Reactive Functionalization of Polyolefin Elastomers Direct Functionalization of Poly(isobutylene-co-p-methylstyrene) by a Friedel-Crafts Acylation Reaction... 

Passaglia, E., Coiai, S., Aglietto, M. et al. 2003. Functionalization of polyolefins by reactive processing Influence of starting reagents on content and type of grafted groups. Macromol Symp. 198 147-160. 

Boaen NK, Hillmyta- MA (2005) Post-polymerization functionalization of polyolefins. Chem Soc Rev 34(3) 267-275... 

Ciardelli, R, Aglietto, M., Ruggeri, G., Passaglia E., and Castelvetro, V. 1997. Functionalization of polyolefins in the melt through reaction with molecules and macromolecules. Macromolecular Symposia 118 311-316. 

There are a few thousand patents on functionalization of polyolefines, and the amount of published papers in open literature is growing fast. Without doubt, the most studied monomer is maleic anhydride (MAH). This is because it contains a functionality for radical reactions and also a cyclic anhydride for other reactions. Copolymerization of polar monomers with ethylene or propylene could be used to improve the polarity of PP or PE, but due to the sensitivity of the Ziegler-type of catalysts used during polyolefin polymerization this is difficult. For this reason, graft copolymerization in the melt is an attractive route to acquire modified polymers and conserve most of the original properties of the materials. 

Scheme 1. Functionalization of polyolefins by reaction with dietylmaleate and dicumylperoxide (DCP).

Aglietto, M., Bertani, R., Ruggeri, G., and Segre, A.L. (1990) Functionalization of polyolefins. Determination of the structure of functional groups attached to polyethylene by free radical reactions. Macromolecules, 23,1928-1933. 

Alternative process to prepare polymeric boronate was rhodium-catalyzed functionalization of polyolefins in the melt [9]. Polyethylethylene (12) was allowed to... 

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