Stereoregular and Stereoirregular Alternating Ethylene−Norbornene Copolymers

Abstract

Ethylene−norbornene (E−N) copolymers were synthesized with the C 2 metallocene rac-Me2Si(2-Me-[e]-benzindenyl)2ZrCl2 (3) and with the constrained geometry Me2Si(Me4Cp)(NtBu)TiCl2 (4) in the presence of methylaluminoxane. The E−N copolymerizations were carried out using a variety of monomer feed compositions. Copolymers were fully characterized by 13C NMR spectroscopy, gel permeation chromatography, and differential scanning calorimetry. Copolymer microstructures were analyzed in detail, through a procedure which accounts for the stoichiometric requirements of the copolymer chain as well as for the measured areas of 13C NMR signals. This analysis, which quantifies the differences in sequence distribution and tacticity of the polymers, evidenced that mainly alternating stereoregular and stereoirregular copolymers were prepared with 3 and 4, respectively. The copolymer prepared with 4 contains both meso and racemic NEN sequences and small amounts of meso and racemic NN diads, while the alternating copolymer prepared with 3 contains only meso NEN sequences and small amounts of meso NN diads. The formation of NN diads is disfavored with both catalysts. Surprisingly, a significant amount of norbornene (up to ∼10%) belonging to NNN triads (T) is obtained with the C 2 catalyst.

Design of Efficient Molecular Catalysts for Synthesis of Cyclic Olefin Copolymers (COC) by Copolymerization of Ethylene and α-Olefins with Norbornene or Tetracyclododecene

“…Many have reported on ethylene copolymerization with norbornene (NBE) using ordinary metallocenes [10][11][12][13][14][15][16][17], half-titanocenes [18][19][20][21][22][23][24][25][26], and others [27][28][29][30], however, successful examples of the efficient synthesis of random, high molecular weight copolymers with high Tg values (high NBE content) have been limited. Ethylene copolymers with tetracyclododecene (TCD, dimethanooctahydronaphthalene) are also known as promising materials [9], and are produced by using classical Ziegler-type vanadium catalyst systems (VOCl3, VO(OEt)Cl2-EtAlCl2•Et2AlCl, etc.)…”

Molecular Dynamics in Cyclic Olefin Copolymer

“…The structure of these copolymers has been extensively studied using 13 C high resolution in solution [5][6][7]. It was found that in copolymer with low NB content the close vicinity of two or more NB groups is rather rare.…”

Microstructure of Copolymers of Norbornene Based on Assignments of 13C NMR Spectra: Evolution of a Methodology

“…The thorough microstructure investigation of E-co-N copolymers has taken several years [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. A number of groups dedicated great efforts to assign the 13 C NMR spectra of E-co-N copolymers.…”

“…Utilizing the observed peak areas of the assigned 13 C signals and accounting for the stoichiometric requirements, it was possible to compute the molar fractions of the stereosequences, which define the microstructure of an alternating E-co-N copolymer containing meso (m) and racemic (r) alternating sequences [26].…”