@article { ISI:000225953600006, title = {In situ polymerization of ethylene with bis(imino)pyridine iron(II) catalysts supported on clay: the synthesis and characterization of polyethylene-clay nanocomposites}, journal = {Journal of Polymer Science Part A-Polymer Chemistry}, volume = {43}, number = {2}, year = {2005}, month = {JAN}, pages = {304-318}, publisher = {JOHN WILEY \& SONS INC}, type = {Article}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

Polyethylene-clay nanocomposites were synthesized by in situ polymerization with 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl] pyridine iron(II) dichloride supported on a modified montmorillonite clay pretreated with methylaluminoxane (MAO). The catalysts and the obtained nanocomposites were examined with wide-angle X-ray scattering. The exfoliation of the clay was further established by transmission electron microscopy. Upon the treatment of the clay with MAO, there was an increase in the d-spacing of the clay galleries. No further increase in the d-spacing of the galleries was observed with the iron catalyst supported on the MAO-treated clay. The catalyst activity for ethylene polymerization was independent of the Al/Fe ratio. The exfoliation of the clay inside the polymer matrix depended on various parameters, such as the clay content, catalyst content, and Al/Fe ratio. The crystallinity percentage and crystallite size of the nanocomposites were affected by the degree of exfoliation of the clay. Moreover, when ethylene was polymerized with a mixture of the homogeneous iron(II) catalyst and clay, the degree of exfoliation was significantly lower than when the polymerization was performed with a preformed clay-supported catalyst. This observation suggested that in the supported catalyst, at least some of the active centers resided within the galleries of the clay. (C) 2004 Wiley Periodicals, Inc.

}, keywords = {clay, In situ polymerization, Nanocomposites, polyethylene (PE), TEM, WAXS}, issn = {0887-624X}, doi = {10.1002/pola.20502}, author = {Ray, S and Galgali, G and Lele, Arundhati C. and Sivaram, S} } @article { ISI:000245141300021, title = {Controlled synthesis of low-molecular-weight polyethylene waxes by titanium-biphenolate-ethylaluminum sesquichloride based catalyst systems}, journal = {Journal of Applied Polymer Science}, volume = {104}, number = {3}, year = {2007}, month = {MAY}, pages = {1531-1539}, publisher = {JOHN WILEY \& SONS INC}, type = {Article}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

Soluble complexes of titanium(IV) bearing sterically hindered biphenols, such as biphenol, 1,1{\textquoteright}-methylene di-2-naphthol, 2,2{\textquoteright}-methylene bis(4-chlorophenol), 2,2{\textquoteright}-methylene bis(6-tert-butyl-4-ethyl phenol), and 2,2{\textquoteright} ethylidene bis(4,6-di-tert-butyl phenol), were prepared and characterized. These catalyst precursors, formulated as [Ti((OO)-O-boolean AND)X-2], were active in the polymerization of ethylene at high temperatures in combination with ethylaluminum sesquichloride as a cocatalyst. The ultra-low-molecular-weight polyethylenes (PEs) were linear and crystalline and displayed narrow polydispersities. The catalytic polymerization leading to PE waxes in this reaction exhibited unique properties that have potential applications in surface coatings and adhesive formulations. (c) 2007 Wiley Periodicals, Inc.

}, keywords = {Catalysts, polyethylene (PE), synthesis, Ziegler-Natta polymerization}, issn = {0021-8995}, doi = {10.1002/app.25525}, author = {Umare, Prashant S. and Rao, Karumanchi and Tembe, Gopal L. and Dhoble, Deepa Arun and Trivedi, Bhavna} } @article {46696, title = {Ultrahigh molecular weight polyethylene: catalysis, structure, properties, processing and applications}, journal = {Progress in Polymer Science}, volume = {109}, year = {2020}, month = {OCT}, pages = {101290}, type = {Review}, abstract = {

Ultrahigh molecular weight polyethylene (UHMWPE) belongs to an emerging class of high-performance specialty polymers with a unique set of properties and applications. The field has witnessed many scientific and technological advances in recent years. However, synthesis of UHMWPE is not a trivial exercise and presents several challenges. This review addresses these fundamental challenges and provides an overview of recent developments in the field of UHMWPE. The nature of catalysts, reaction conditions that favor its formation, their physical properties, methods of processing them into products, and their applications are discussed. Recent developments in formation of UHMWPE in a disentangled state by use of appropriate catalysts and reaction conditions are also discussed. This has elicited considerable interest as a means of enabling melt processing of UHMWPE. This review provides a comprehensive source of information and understanding of the multifaceted aspects of UHMWPE with specific reference to chemistry, catalysis, processes for manufacturing, and an analysis of catalyst structure-polymer property relationships. (C) 2020 Elsevier B.V. All rights reserved.

}, keywords = {Catalysts for UHMWPE, Disentangled UHMWPE, Entangled UHMWPE, polyethylene (PE), Ultrahigh molecular weight (UHMW) PE}, issn = {0079-6700}, doi = {10.1016/j.progpolymsci.2020.101290}, author = {Patel, Ketan and Chikkali, Samir H. and Sivaram, Swaminathan} }