Preparation of Functional Polyethylenes by Catalytic Copolymerization

Abstract

b S Supporting Information T he physical properties of polyethylene (PE) can be drastically altered by careful manipulation of its microstructure and particularly by controlling the length and distribution of alkyl branches along the chain. Instead of alkyl chains, it would be desirable to introduce low amounts of polar groups because they are expected to greatly impact the toughness, flexibility, crack resistance, gas permeability, miscibility, adhesion, and paintability of PE. 1 These copolymers are also of prime importance for the formation of nanocomposites since the presence of polar groups enhances compatibility between the polymeric matrix and the dispersed charge. 2 However, catalytic polymerization of readily available polar monomers is still one of the major challenges in the field of olefin polymerization. 3 Among all polar monomers, those bearing easily functionalized groups such as carboxylic acid and anhydrides would offer a unique opportunity for the direct preparation of functional PEs.Polymers bearing anhydride functionalities can be prepared by reactive extrusion of molten PE in the presence of maleic anhydride (MA) and a radical initiator. This radical process not only grafts the anhydride as a pendant group but also generates several undesirable side reactions such as chain scission and chain branching. 4 Radical copolymerization of ethylene with acrylic acid (AA) or methacrylic acid yields ionomers, 5 that is to say, thermoplastics containing acid groups converted to metal salts which act as physical cross-links. These commercially important polymers are used in a variety of applications, including orthodontics and prosthetics, as films, adhesive layers in foil/ paper containers, and as constituents of items such as golf balls and bowling pins. We recently demonstrated that linear copolymers of ethylene and AA exhibit higher crystallinity and melting points than their branched counterparts. 6 Furthermore, in water they self-assemble into thermosensitive nanoparticles. These copolymers were prepared by catalytic copolymerization of ethylene with tert-butyl acrylate followed by deprotection of the ester. Clearly, it would be advantageous to prepare these copolymers by direct copolymerization with AA.We have probed the preparation of functional PE by catalytic copolymerization of ethylene with AA, MA, and carbic anhydride (CA, 5-norbornene-endo-2,3-dicarboxylic anhydride) using Pdbased well-defined catalysts 1 or 2 (Scheme 1). The choice of these catalysts is motivated by the fact that Pd phosphine aryl sulfonates allow for the copolymerization of a wide range of monomers, such as acrylonitrile, 7 vinyl ethers, 8 vinyl esters, 9 vinyl fluoride, 10 acrylates, 11-14 norbornenes, 15,16 styrenes, 17 vinyl ketones, 17 acrylamides, 18 N-vinylpyrrolidone, 18 vinyl sulfones, 19

Copolymers of ethylene and sulfonated norbornene for proton exchange membranes

“…The polymer is prepared by the terpolymerization of ethylene, NBE, and 5‐ exo norbornene methyl alcohol ( exo ‐NBE‐CH 2 OH), using a phosphine sulfonate catalyst (Scheme ). The choice of this catalyst is motivated by the observation that phosphine sulfonate catalysts offer unprecedented functional group tolerance for the copolymerization of a wide range of polar olefins with ethylene and most notably for the copolymerization of ethylene with NBE …”

“…The choice of this catalyst is motivated by the observation that phosphine sulfonate catalysts offer unprecedented functional group tolerance for the copolymerization of a wide range of polar olefins with ethylene 29,30,[32][33][34][35][36][37][38][39][40][41][42][43][44] and most notably for the copolymerization of ethylene with NBE. 42,[45][46][47] Initial experiments aimed at preparing a NBE monomer containing a SO 3 H group. Since it has recently been demonstrated by the group of Tritto that the reactivity of exo monomers is greater than endo monomers, 47 our monomer synthetic scheme was devised so as to obtain NBEs bearing a substituent exclusively in the 5-exo position.…”

High‐Impact Polyamide Composites with Linear Ethylene–Norbornene Anhydride Copolymers from Insertion Polymerization

“…Additionally, low polymerization activities are often observed due to reversible intra-and intermolecular deactivation by coordination of the functional groups present to the palladium center. Intriguingly, norbornene [13,14] and some of its functional derivatives, [15] such as norbornene anhydride, [16] are exceptions to these trends observed for other polar monomers such as acrylic acid, [17] maleic anhydride, [16] or acrylates. [6,18,19] Chain transfer is even less pronounced after the incorporation of a norbornene anhydride unit into the growing chain than for ethylene leading to an increase of molecular weight with increasing norbornene anhydride content in the copolymer.…”

Direct Synthesis of Telechelic Polyethylene by Selective Insertion Polymerization

“…Under pressure-reactor conditions,e xposure of L1Pd to 5bar of Eand 0.075 m of VF at 95 8 8Cresulted in the formation of ac opolymer with al ow VF incorporation of 0.4 mol %( Table 1, entry 1). Preliminary 1 Ha nd 13 CNMR spectra of this E-VF copolymer indicated that incorporated VF is overwhelmingly (95 %) located in both saturated (S) chain ends and unsaturated (US) chain ends,inaratio of ca. 1:1( S VF :US VF = 44 %:51 %).…”