New Polyethylene Macroinitiators and Their Subsequent Grafting by Atom Transfer Radical Polymerization

Abstract

A semicrystalline polyethylene (PE) macroinitiator was prepared by copolymerizing ethylene and an inititating monomer (5-norbornen-2-yl-2'-bromo-2'-methyl propanoate) (3) using [N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)isobutanamidato]-Ni(eta1-CH2Ph)(PMe3) (1) and Ni(COD)2 (bis(1,5-cyclooctadiene)-nickel) (2). Although 3 decomposes Ni(COD)2, if the initiating species (1/2) are exposed to ethylene for a period of time, t1, and then 3 is introduced for another period of time, t2, the polymerization takes place in a controlled manner. Variations in temperature, pressure, and [3] afford a great deal of control over the composition and architecture of the PE macroinitiator. Subsequent grafting with methyl methacrylate (MMA) yields PE-graft-PMMA with narrow polydispersities and increasing PMMA content at longer reaction times. Because the products are semicrystalline materials with high melting points, they are anticipated to function as blend compatibilizers for linear polyethylene.

Olefin Polymerization with Non-metallocene Catalysts (Late Transition Metals)

“…Addition of B(C 6 F 5 ) 3 leads to increase of the catalytic activity and Benzyl Ni complex with a-iminocarboxamide ligand (7d) is formed by the reaction of potassium salt of the carboxyamide with the Ni complex having a p-benzyl ligand [120]. The reaction with Ni(cod) 2 cocatalyst affords the phosphine-free intermediate, which catalyzes quasi-living polymerization of ethylene as well as copolymerization of ethylene with functionalized norbornene [121,122]. Bulky aryl groups on both the nitrogens favor formation of the N,O-coordinated complex, which is active for ethylene polymerization [123,124].…”

Synthesis and Characterization of Semicrystalline Polyethylene‐graft‐Poly(acrylic acid) Copolymers

“…Reagents, unless otherwise specified, were purchased from Aldrich and used without further purification. N-(2,6-Diisopropylphenyl)-2-(2,6-diisopropylphenylimino)isobutanamidato]Ni(h 1 CH 2 Ph)(PMe 3 ) (1), [16] and 5-norbornen-2-yl-2-bromo-2-methylpropanoate (3) [15] were synthesized as previously reported. Bis(1,5-cyclooctadiene) nickel (2) was purchased from Strem.…”

“…Because 2 decomposes in the presence of 3, it is necessary to grow a short PE block (32 kg Á mol À1 for t 1 ¼ 3 min at 100 psi) before introducing 3 to the reaction mixture; this technique has been previously shown to produce PE macroinitiators in a controlled manner. [15] Accordingly, at 20 8C and 100 psi of C 2 H 4 , using 0.06 M of 3 added at the completion of t 1 , three different macroinitiators were prepared to probe the effect of inimer content and molecular weight on the physical properties of products. The incorporation of 3 was varied by decreasing ethylene pressure from 100 (PEC1) to 50 psi (PEC2), while different molecular weights were achieved by changing the total polymerization time from 5 (PEC1) to 15 min (PEC3).…”

“…The use of anisole as the solvent results in a controlled ATRP process, as does the addition of a small amount of deactivator, CuBr 2 . [15,20] Accordingly, a series of graft copolymers was prepared as shown in Scheme 2. Briefly, PE macroinitiator was dissolved in an anisole solution containing CuBr and CuBr 2 ligated with PMDETA.…”

“…Previously, we have shown that the neutral nickel a-iminocarboxamidato complex (1) is capable of copolymerizing C 2 H 4 and an initiating comonomer or inimer (3), when activated with nickelbis(1,5-cyclooctadiene) (2) or Ni(COD) 2 . [15] This system enables control over inimer incorporation, the number-average molecular weight (M n ) and the higher-order architecture of the products, while maintaining narrow PDIs. In this contribution, we describe the synthesis and characterization of polyethylene-graft-poly(tert-butyl acrylate) (PE-gPtBA) materials generated by grafting tBA from PE macroinitiators using ATRP.…”