Analysis of Ethylene Copolymers with Long-Chain α-Olefins (1-Dodecene, 1-Tetradecene, 1-Hexadecene): A Transition between Main Chain Crystallization and Side Chain Crystallization

Abstract

A series of ethylene copolymers with long-chain α-olefins [LCAOs, 1-dodecene (DD), 1-tetradecene (TD), 1-hexadecene (HD)] and various LCAO contents were prepared, and their thermal properties, including effects of LCAO content and side chain length, were explored. The Cp*TiCl 2 (O-2,6- i Pr 2 -4-SiEt 3 -C 6 H 2 )–MAO catalyst system afforded rather high-molecular-weight copolymers with unimodal molecular weight distributions and uniform compositions (confirmed by DSC thermograms). In addition to the melting temperatures ( T m values) corresponding to the so-called main chain crystallization (samples with low LCAO contents, the T m value decreased upon increasing the LCAO content) and the side chain crystallization [polymer samples with high LCAO contents, by intermolecular interaction of side chains as observed in poly(DD), poly(TD), and poly(HD)], the other T m value was observed, especially in poly(ethylene- co -HD)s (assumed to be due to co-crystallization of the branch and the main chain through an interaction of the main chain and the long side chains). The presence of another crystalline phase in poly(ethylene- co -HD)s was also suggested by a wide-angle X-ray diffraction (WAXD) analysis. These T m values in poly(ethylene- co -TD)s and poly(ethylene- co -DD)s with rather high TD or DD contents were affected by the heating conditions in the measurement of DSC thermograms (5 or 10 °C/min), suggesting that the driving force for formation of the crystal packing (observed as T m ) is weak and affected by the alkyl side chain lengths.

Polymerization of α-olefins and their copolymerization with ethylene by half-sandwich scandium catalysts with an N-heterocyclic carbene ligand

“…When 1-dodecene was above 15.0 mol%, the copolymers possessed a T m at 110 °C originating from polyethylene and another T m from −35 °C to −25 °C as the 1-dodecene incorporation increased from 15.0 mol% to 51.8 mol% originating from intermolecular arrangement of the side chain of 1-dodecene in 1-dodecene-ethylene copolymers. 69 The T m originating from polyethylene disappeared when the 1-dodecene incorporation content increased to 27.3 mol% (Fig. 4c).…”

“…1–5 The fine-tuning of the stereo-electronic properties of the ancillary ligands in homogeneous catalysts proved to be a key tool for controlling the reactivity and catalytic performances. 6–10 The most extensively investigated catalysts for the polymerization of α-olefins and their copolymerization with ethylene are group 4 metallocene catalysts, 2,4,10–17 constrained geometry catalysts (CGC), 3,6,7,18 and post-metallocene catalysts. 5,8,9,19–22 Rare-earth metal catalysts have attracted a great deal of attention during the past two decades due to their unique catalytic performance in a variety of polymerization reactions of compounds such as ethylene, styrene, 1,3-conjugated dienes, polar monomers, etc .…”

“…The development of efficient catalysts for the polymerization of α-olefins and their copolymerization with ethylene to synthesize high-performance polyolefins has been the subject of intense scrutiny in both academic and industrial research. [1][2][3][4][5] The fine-tuning of the stereo-electronic properties of the ancillary ligands in homogeneous catalysts proved to be a key tool for controlling the reactivity and catalytic performances. [6][7][8][9][10] The most extensively investigated catalysts for the polymerization of α-olefins and their copolymerization with ethylene are group 4 metallocene catalysts, 2,4,10-17 constrained geometry catalysts (CGC), 3,6,7,18 and post-metallocene catalysts.…”

Phase Behavior and Ionic Conductivity of Blended, Ion-Condensed Electrolytes with Ordered Morphologies

“…At lower temperatures, the single peak in the WAXS region at ~1.5 Å −1 observed for the majority of mixtures is indicative of hexagonal [100] packing of the alkyl chains [27][28][29]. Upon crystallization of the blends, the primary reflections in the SAXS region remain, with increased intensity, while additional minor peaks emerge.…”

Effect of Borate Cocatalysts toward Activity and Comonomer Incorporation in Ethylene Copolymerization by Half-Titanocene Catalysts in Methylcyclohexane

“…Linked half-titanocene called constrained geometry type, [Me 2 Si­(C 5 Me 4 )­(N t Bu)]­TiCl 2 ( 1 ), have been chosen in this study because 1 shows efficient comonomer incorporation especially of long chain α-olefins in the ethylene copolymerization. ,− The phenoxide modified half-titanocenes, Cp*TiMe 2 (O-2,6- i Pr 2 -4-R′C 6 H 2 ) [R′ = H ( 2 ), SiEt 3 ( 3 )], have also been chosen because these catalysts display efficient comonomer incorporations in the ethylene (E) copolymerizations not only with 1-dodecene (DD) − but also with 2-methyl-1-pentene (2M1P) , and vinylcyclohexane (VCH), which are not incorporated by the ordinary (metallocene) catalysts. The dimethyl complex ( 3 ) was newly prepared by treating Cp*TiMe 3 with 2,6- i Pr 2 -4-SiEt 3 C 6 H 2 OH in Et 2 O according to the published method for synthesis of 2 and was identified by NMR spectra and elemental analysis (shown in the Supporting Information, SI).…”