46th IUPAC POLYMER CONGRESS , 2016-07-17

Title : ( α-Diimine binuclear Ni-based catalysts for ethylene polymerization: effect of ortho-substituent )

Authors: mostafa khosh sefat , Saeid Ahmadjo , Seyed Mohammad Mehdi Mortazavi , Gholamhossein Zohuri , Majid Zahmaty , Khosrow Valieghbal ,

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Two binuclear α-diimine nickel (II) catalyst (A) 2,6-diisopropyl-C6H2-N=C(C10H6)-C=N-C6H4-N=C-(C10H6)-C=N-2,6-diisopropyl-C6H2NiBr2 and 2,6-diisopropyl-C6H2-N=C-(C10H6)-C=N-C6(CH3)4-N=C-(C10H6)-C=N-2,6-diisopropyl-C6H2NiBr2 (B) were prepared and used in ethylene polymerization. To investigate ortho-substituent effect (methyl) on catalyst behavior and produced polyethylene (PE) properties, the experiments were performed under similar condition and methylaluminoxane (MAO) was used as cocatalyst. Catalyst B (1645 g PE/mmolNi. h.) showed higher catalytic performance in comparison catalyst A (1073 g PE/mmolNi. h.). The vinyl content and branching of resulted PE in presence of cat A were 9.1 and 78 (in 1000 carbon atom), however, these quantities decreased to 7.2 and 59 for cat B, respectively. These observations assigned to lower steric and electronic effects of substituents onthe ortho-position of middle aryl ring (hydrogens in cat A) which can cause dissociation of the chain along with vinyl-end and reinsertion of the macromonomers lead to branches producing [Capacchione et al., 2015]. Besides, methyl groups in cat B caused retarding β-hydrogenelimination and chain transfer due to reducing monomer diffusion from ortho-position tometallic center [Merna et al., 2009]. These mechanistic reasons reduce vinyl and branching content in cat B. DSC analysis showed a peak along with a broad shoulder for both synthesized polymer using cat A and B. The broadening transition has been attributedto a sequence of melting followed byrecrystallization steps of less ordered domainswith the variable amounts of chainbranching [Pourmahdian et al., 2011]. The crystallinity contents and melting points were 24.7% and 123.0 ˚C for cat A and 41.3% and 112.2 ˚Cfor cat B. Based on aforementioned reason for branching, cat B which has methyl groups on ortho position instead of hydrogens in cat A, produce less branching with higher crystallinity.

Keywords

, Keywords: polyethylene, catalytic polymerization, binuclear catalyst, structure dependence, post metallocene Keywords: polyethylene, catalytic polymerization, binuclear catalyst, structure dependence, post metallocene Keywords: polyethylene, catalytic polymerization, binuclear catalyst,
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@inproceedings{paperid:1057804,
author = {Khosh Sefat, Mostafa and Saeid Ahmadjo and Seyed Mohammad Mehdi Mortazavi and Zohuri, Gholamhossein and Majid Zahmaty and Khosrow Valieghbal},
title = {α-Diimine binuclear Ni-based catalysts for ethylene polymerization: effect of ortho-substituent},
booktitle = {46th IUPAC POLYMER CONGRESS},
year = {2016},
location = {Istanbul},
keywords = {Keywords: polyethylene; catalytic polymerization; binuclear catalyst; structure dependence; post metallocene Keywords: polyethylene; catalytic polymerization; binuclear catalyst; structure dependence; post metallocene Keywords: polyethylene; catalytic polymerization; binuclear catalyst; structure dependence; post polyethylene; catalytic polymerization; binuclear catalyst; structural dependence; metallocene},
}

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%0 Conference Proceedings
%T α-Diimine binuclear Ni-based catalysts for ethylene polymerization: effect of ortho-substituent
%A Khosh Sefat, Mostafa
%A Saeid Ahmadjo
%A Seyed Mohammad Mehdi Mortazavi
%A Zohuri, Gholamhossein
%A Majid Zahmaty
%A Khosrow Valieghbal
%J 46th IUPAC POLYMER CONGRESS
%D 2016

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