Polyolefin macromonomer

Radical induced grafting may be carried out in solution, in the melt phase,292 29 or as a solid state process.296 This section will focus on melt phase grafting to polyolefin substrates but many of the considerations are generic. The direct grafting of monomers onto polymers, in particular polyolefins, in the melt phase by reactive extrusion has been widely studied. Most recently, the subject has been reviewed by Moad1 9 and by Russell.292 More details on reactive extrusion as a technique can be found in volumes edited by Xanthos," A1 Malaika and Baker et a 21 7 The process most often involves combining a frcc-radical initiator (most commonly a peroxide) and a monomer or macromonomer with the polyolefin as they are conveyed through the extruder. Monomers commonly used in this context include MAII (Section 7.6.4.1), maleimidc derivatives and malcate esters (Section 7.6.4.2), (meth)acrylic acid and (meth)acrylate esters (Section 7.6.43), S, AMS and derivatives (Section 7.6.4.4), vinylsilancs (Section 7.6.4.5) and vinyl oxazolines (Section 7.6.4.6). 

In this article, we would like to review recent advances in polymer hybrids based on polyolefins and to classify them into four methodologies, namely, PO macroinitiator, PO macromonomer, reactive PO and living copolymerization of olefins, with their well-defined structures and applications. 

End-functionalized polyethylene (PE) [8, 9], polypropylene (PP) [10], and polyisobutylene (PIB) [11] have been transformed to their corresponding macromonomers carrying (meth)acrylate, oxazoline, and methacrylate end groups, 1, 2, and 3, respectively. Polybutadienyl lithium was terminated with chlo-rodimethylsilane, followed by hydrogenation to saturated polyolefin (PHBd) [12]. Hydrosilylation of the end silane with allyl glycidyl ether afforded an epox-... 

Polyolefin blends always show a raised swell of the extrudate jet in comparison with homopolymers (83). This was shown earlier (88) for LDPE/LLDPE blends. Some researchers reported (89,90) a significant influence of the molecular structure on properties of the polymer melts the polymers whose chains contain starlike branches show increased sensitivity toward shear stresses applied onto their melts. The presence of comblike segments increases the melt strength. For example, the addition to LLDPE up to 10 wt% of a comblike polymer (copolymer of a polyethylene macromonomer, k. 8000gmol , and ethylene and hexene) allows raising the strength of polymer melt almost by one decimal order (86). The MFl of the blend varies less substantially. The melt strength of LLDPE blends can be... 

Cherian, A.E., Lobkovsky, E.B., and Coates, G.W. (2005a) Synthesis of allyl-terminated syndiotactic polypropylene macromonomers for the synthesis of branched polyolefins. Macromolecules, 38,6259-6268. 

A solution to the steric bulk of the macromonomers is grafting from where polymerizations occur from the functionalized side chains of the ROMP-generated backbone. The copolymerization of propylene with 4mol% GOD yielded terminal vinyl groups off the main polymer chain resulting from the addition of the GOD. Attachment of the catalyst at the vinyl group via olefin metathesis enabled ROMP of nor-bomene derivatives from the polyolefin backbone.In a grafting from approach, norbornene monomers with covalently attached ATRP initiators were copolymerized with ester-functionalized norbomenes to form the polymeric backbone. The ATRP of acrylic acid successfully yielded the brush polymer. 

The reactive metal-polymeryl bond has been used to form various chain end functional polyolefins, including hydro-xyls, " azides, amines, and iodo-funcdonal materials (Scheme 16). A number of PEs bearing initiators for free-radical polymerizations and macromonomers have been reported in recent years. These building blocks have been used to synthesize a variety of functional polyolefin block and graft copolymers. These materials show pronuse for improved compatibility and adhesion to polar materials. 

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