Functionalized polyolefins

These are the logical condusion of the work with unsaturated acids and anhydrides discussed above, and are gaining considerable importance in thermoplastic 

A variety of commercial products specifically aimed at being used in filled polymers are available, notably from Arkema (Lotader and Orevac ), DuPont (Fusabond ), Westlake Chemicals (Epolene ), ExxonMobil (Exxelor ), and Crompton (Polybond ). The terminology used in this discussion is as follows acrylic acid grafted PE or PP=AA-g-PE or AA-g-PP maleic anhydride grafted = MA-g-PE or MA-g-PP. 

In some cases, copolymerization is used. Typical of the products made in this way are terpolymers of ethylene, n-butyl acrylate, and maleic anhydride, such as the Lotader products from Arkema, which have proved to be very good coupling agents in filled EVA copolymers. 

most commercial products for filler applications appear to be based on maleic anhydride, rather than acrylic acid, and what comparative data are available suggest that the maleated forms are the more effective and can be used at lower levels. The acrylic acid forms have higher functionality levels than the maleated ones. 

Mai et al. reported on the use of AA-g-PP in aluminum hydroxide-filled PP homopolymer [41] and found the graft polymer to increase filler to polymer wetting and adhesion, as shown by electron microscopy of fracture surfaces. In addition, they found not only significant increases in fiexural strength but also a loss in notched impact strength. The loss in impact strength was most marked at low to moderate filler levels and was least at the 60% level, typical for fire-retardant compounds. It was 

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Blends based on polyolefins have been compatibilized by reactive extrusion where functionalized polyolefins are used to form copolymers that bridge the phases. Maleic anhydride modified polyolefins and acrylic acid modified polyolefins are the commonly used modified polymers used as the compatibilizer in polyolefin-polyamide systems. The chemical reaction involved in the formation of block copolymers by the reaction of the amine end group on nylon and anhydride groups or carboxylic groups on modified polyolefins is shown in Scheme 1. 

Since a thorough review of the scientific and patent literature failed to produce any information relative to die preparation of silicon-functional polyolefins by cationic methods, this untapped field appeared particularly attractive for systematic research. Added justification for this objective was provided by the possible exploitation of the vast synthetic possibilities offered by a combination of the chemistries of cationic polymerization and that of organosilanes24. ... 

SYNTHETIC METHODS SILICON-CONTAINING POLYMERS, FUNCTIONALIZED POLYOLEFINS, AND TELECHELICS... 

Friedel-Crafts catalysts, 329, 331 Friedel-Crafts reaction, 297, 361 Front-end reactions, 235 FT Raman spectroscopy, 387 FTIR spectrometry. See Fourier transform infrared (FTIR) spectrometry Fuel cells, 272-273 Full prepolymers, 236, 237 Functionalized polyolefins, 459-460... 

Hartwig and Hillmyer have recently reported the Rh-catalyzed borylation of polyolefins to yield boronate-functionalized polymers (58) (Fig. 37) in a single step.83 The number-average molecular weight of the borylated polymer that was obtained at a B2pin2 polyethylethylene ratio of 0.3 was found to be the highest (Mn = 52,000 and PDI = 1.09) among the developed boronate-functionalized polyolefins. 

Referring to the ADMET mechanism discussed previously in this chapter, it is evident that both intramolecular complexation as well as intermolecular re-bond formation can occur with respect to the metal carbene present on the monomer unit. If intramolecular complexation is favored, then a chelated complex, 12, can be formed that serves as a thermodynamic well in this reaction process. If this complex is sufficiently stable, then no further reaction occurs, and ADMET polymer condensation chemistry is obviated. If in fact the chelate complex is present in equilibrium with re complexation leading to a polycondensation route, then the net result is a reduction in the rate of polymerization as will be discussed later in this chapter. Finally, if 12 is not kinetically favored because of the distant nature of the metathesizing olefin bond, then its effect is minimal, and condensation polymerization proceeds efficiently. Keeping this in perspective, it becomes evident that a wide variety of functionalized polyolefins can be synthesized by using controlled monomer design, some of which are illustrated in Fig. 2. 

Recent advances in the development of well-defined homogeneous metallocene-type catalysts have facilitated mechanistic studies of the processes involved in initiation, propagation, and chain transfer reactions occurring in olefins coordi-native polyaddition. As a result, end-functional polyolefin chains have been made available [103].For instance, Waymouth et al.have reported about the formation of hydroxy-terminated poly(methylene-l,3-cyclopentane) (PMCP-OH) via selective chain transfer to the aluminum atoms of methylaluminoxane (MAO) in the cyclopolymerization of 1,5-hexadiene catalyzed by di(pentameth-ylcyclopentadienyl) zirconium dichloride (Scheme 37). Subsequent equimolar reaction of the hydroxyl extremity with AlEt3 afforded an aluminum alkoxide macroinitiator for the coordinative ROP of sCL and consecutively a novel po-ly(MCP-b-CL) block copolymer [104]. The diblock structure of the copolymer... 

Polyolefins with vinyl end groups can be readily transformed into end-functionalized polyolefins by post-polymerization functionalization to yield a wide variety of end-functionalized polyolefins, which include epoxy-, amine-, and hydroxy-terminated polyolefins. Brookhart, Gibson, and co-workers reported on diimine-pyridine-ligated Fe complexes incorporating sterically less hindered alkyl substituents such as a methyl group ortho to the imine-A s, F12-1, that selectively converted ethylene to oligomers, affording linear a-olefin mixtures (>99%) (see also Section... 

These vinyl group-containing polymers may serve as new building blocks in the synthesis of functionalized polyolefins and polyolefin- and polar polymer-based block and graft co-polymers. 

Living olefin polymerization allows the synthesis of end-functionalized polyolefins if appropriate initiation and/or quenching methods are used. Doi et al. first showed the utility of living olefin-polymerization catalysts for the preparation of end-functionalized polyolefins. They synthesized iodine-, amine-, aldehyde-, hydroxy-, and metha-cryl-terminated PPs using living V-PP species and appropriate reagents. " " ... 

The processes described in Table 2 present a peculiar interest in the working out of new materials as polyurethanes. These last polymers are very often based on macro diols coming from polyethers or polyesters, a-co functional polyolefins being relatively uncommon. Hence, Rhein and Ingham [139] prepared macrodiols by ozonization of polyisobutylene in CC14 at... 

So far, theoretically, there have been two possible approaches for the synthesis of functional polyolefins, namely, (a) direct copolymerization of olefins with functional monomers using polymerization and catalyst technologies, and (b) post-polymerization reaction with polyolefins. 

The concept of PO macroinitiators centers on the introduction of an initiation moiety into an olefinic polymer chain for polymerization. The most effective route for preparing PO macroinitiators is by employing functional polyolefins containing hydroxyl groups or other reactive groups. These functional POs are prepared by copolymerization of olefins with functional monomers and post-polymerization reaction, as mentioned above. In the case where an initiation moiety was at the chain-end of the polyolefins, a block type copolymer is produced. It has been reported that thiol-terminated PP was used as polymeric chain transfer agent in styrene and styrene/acrylonitrile polymerization to form polypropylene-b/odc-polystyrene (PP-b-PS) and polypropylene-btock-poly(styrene-co-acrylonitrile) (PP-b-SAN) block copolymer [19]. On the other hand, polymer hybrids with block and graft structures can be produced if initiation moieties are in the polymer chain. 

Bulk grafting of polyolefins with functionalized monomers can be performed by means of conventional processing equipment. Inherently stabilized polyolefins are formed when low concentrations of functionalized monomers are used [218]. Using high concentration levels of the latter, stabilizer masterbatch for blending with undoped polyolefins are created. -Functionalized polyolefins can be prepared by means of the radical grafting more successfully than via copolymerization. 

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