Synthesis Of Polyolefins Research Articles

Recovery of molecular weight distributions from transformed domains. Part I. Application of pgf to mass balances describing reactions involving free radicals

We present a general framework for the application of a transform technique, probability generating functions (pgf), to mass balances that describe free radical reactions, in particular synthesis or modification of polyolefins. Contributions of specific reactions to the mass balances are identified and transformed separately, so that a modular approach is possible for the construction of the pgf balance equations for different free radical processes. This simplifies the transformation step hopefully making the method useful to more people. Three examples taken from the literature are transformed using this modular method showing its ease of use. In Part II of this work, the resulting transforms are inverted to recover the complete molecular weight distribution.

Recent developments in polyolefin characterization

The synthesis and characterization of polyolefins continues to be one of the most important areas for academic and industrial research. One consequence of the development of new tailor-made polyolefins is the need for new and improved analytical techniques for the analysis of polyolefins with respect to molar mass and chemical composition distribution. The present article briefly reviews different new and relevant techniques for polyolefin analysis. The analysis of copolymers by combining high-temperature GPC and FTIR spectroscopy yields information on chemical composition as a function of molar mass. Crystallization analysis fractionation is a powerful new technique for the analysis of short-chain branching in LLDPE and the analysis of polyolefin blends. Additives in polyolefins can be determined efficiently by pyrolysis-gas chromatography-mass spectrometry.

Controlled polymer synthesis in homogeneous and heterogeneous processes

Research in polymer synthesis can be oriented toward method or structure. This review is intended to document both approaches. Recent examples from our own work as well as future prospectives will be presented. A general concern is to work out the impact from organic and supramolecular chemistry. Examples of method oriented work are (i) a unique polycondensation via carbon sulfur-bond formation providing hybrid structures of, e.g., polyphenylenesulfide and polyaniline; (ii) a triazoline additive establishing a novel self-regulation process in controlled radical polymerization; (iii) a metallocene catalyzed polyolefin synthesis which is performed by using “smart”, reversibly cross-linked polymer resins as support; and (iv) hydrogen-bonded aggregates suggesting new emulsifiers for emulsion polymerization thus leading to functional nanoparticles. Examples of structure oriented work are (i) rod-coil block copolymers (1D case) as a “covalently bound combination” of rigid and flexible segments whereby a key synthetic concern is the chemical modification and quantitative end-functionalization of polyphenylene chains; (ii) discs (2D case) as molecularly defined graphite subunits which are obtained via a remarkably mild intramolecular cyclodehydrogenation; and (iii) dendrimers (3D case) as shape-persistent nanoparticles whose high degree of structural precision results from a new cycloaddition-deprotection protocol.

Mathematical Modelling and Control of Chemical Composition Distribution of Ethylene/α-Olefin Copolymers Made with Single and Combined Metallocene Catalysts

ABSTRACTThe single-site nature of metallocene catalysts permits the production of polyolefins with narrow distributions of molecular weight, chemical composition and comonomer sequence length. This enhanced control over polymer chain microstructure permits, in principle, the synthesis of polyolefins with well-controlled properties. In order to benefit from this enhanced control, one needs to understand how polymerization conditions and catalyst type affect polymer microstructure, as well as how the existing characterization techniques can be used to determine their microstructure. This manuscript investigates the effect of polymerization conditions and catalyst type on the chemical composition distribution (CCD) of ethylene/α-olefin copolymers made with single-site and Ziegler-Natta catalysts. Mathematical models will be used to describe CCD of polyolefins made on single- and multiple-site-type catalysts. Crystallization analysis fractionation (CRYSTAF) and temperature rising elution fractionation (TREF) ...

New catalysts for olefin polymerization: from elementary processes to the synthesis of polyolefins

New catalysts for olefin polymerization: from elementary processes to the synthesis of polyolefins

New catalysts for olefin polymerization: from elementary processes to the synthesis of polyolefins

A general investigation of the elementary reactions involved in the activation processes of zirconocene and Ni-based derivatives by methylaluminoxane (MAO) was performed through the association of polymerization kinetics and spectroscopic investigation of the catalytic system. This study demonstrates the close correlation between polymerization activities and the changes in the UV/visible characteristic absorption bands of the transition metal derivative used as catalyst. Hex-1-ene was chosen as model monomer.

Synthesis and characterization of polyolefin–silicate nanocomposites: a catalyst intercalation and in situ polymerization approach†

An organically modified fluorohectorite intercalated by a well-defined cationic palladium complex forms an exfoliated polyolefin–silicate nanocomposite material when exposed to olefinic monomer.

Developments in the synthesis of maleated polyolefins by reactive extrusion

AbstractThe maleation of conventional and metallocene linear low density polyethylenes by reactive extrusion has been explored with a view to defining the conditions necessary for a robust process that provides both high grafting efficiencies (>80%) and minimal degradation or cross‐linking. The dependence of grafting efficiency on various operating parameters (maleic anhydride level, maleic anhydride:initiator ratio, throughput rate, direction of screw rotation, temperature) has been established. Literature methods for characterization of the grafted product based on FTIR or 1H NMR analysis have been critically examined with respect to their ability to distinguish between single unit and oligomeric maleic anhydride grafts and found to yield ambiguous results.

ω‐Chloro‐α‐olefins as co‐ and termonomers for the synthesis of functional polyolefins

AbstractThis paper deals with the use of ω‐chloro‐α‐olefins as monomers for the synthesis of chloro‐functional homo‐, co‐ and terpolyolefins in the presence of (IVb) metallocene/MAO catalytic systems. Two ω‐chloro‐α‐olefins, 11‐chloroundec‐1‐ene and 5‐chloropent‐1‐ene, were tested. It was found that only the functional olefin containing the longer aliphatic spacer between the alkene function and the halide polymerizes readily in the presence of the rac‐Et(Ind)2ZrCl2/MAO catalyst. The drastic influence of the reaction solvent on the chloro‐olefin reactivity and (co)polymerization behavior is examined and discussed. Finally, the terpolymerization of 11‐chloroundec‐1‐ene with ethylene and propene is investigated. In a second part, the quantitative preparation, by derivatization of 11‐chloroundec‐1‐ene units, of functional polyolefins bearing benzoate, hydroxy or azido functions as side groups is described. The corresponding functional polymers are characterized by IR and 1H NMR spectroscopy.

Silanes as Chain Transfer Agents in Metallocene-Mediated Olefin Polymerization. Facile in Situ Catalytic Synthesis of Silyl-Terminated Polyolefins

Silanes as Chain Transfer Agents in Metallocene-Mediated Olefin Polymerization. Facile in Situ Catalytic Synthesis of Silyl-Terminated Polyolefins

Crystal Structure, Morphology, and Phase Transitions in Syndiotactic Polypropylene

Abstract The discovery of a new catalyst for the low temperature and low pressure polymerization of ethylene by Ziegler at the Mulheim Institute in Germany in the mid-1950s opened the door to a whole new world in the synthesis of polyolefins [1]. Shortly thereafter, Natta and his group at the Milan Insti-tute in Italy announced that propylene and higher a-olefins could also be polymerized by the use of coordination catalysts, for example Tic], -Al(eth), F [2, 3]. The discovery of stereospecific polymerization allowed steric control on the growth of polymer chains for the first time. A major consequence of this polymerization is a significant effect of stereoregularity on physical, in particular, and mechanical properties. Another major con-tribution by Natta and his group was the development of methods for characterizing polymer configurations and conformations.

Synthesis of Diblock Polyolefin and Polyester Copolymers Using Zirconium and Aluminum Catalysts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis of Diblock Polyolefin and Polyester Copolymers Using Zirconium and Aluminum CatalystsAnne-Lise Mogstad and Robert M. WaymouthCite this: Macromolecules 1994, 27, 8, 2313–2315Publication Date (Print):April 1, 1994Publication History Published online1 May 2002Published inissue 1 April 1994https://doi.org/10.1021/ma00086a050RIGHTS & PERMISSIONSArticle Views234Altmetric-Citations25LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (328 KB) Get e-Alerts Get e-Alerts

Synthesis of recyclable polyolefins from α,ω‐dihydroxypolybutadiene using condensation and hydrogenation reactions

A polyolefin-like polymer was synthesized by condensation reaction of α,ω-dihydroxypolybutadiene with sebacoyl dichloride followed by hydrogenation. The resulting polymer was subjected to hydrolysis to recover α,ω-dihydroxypolybutadiene

Prospects for expansion of research in the field of polyolefin synthesis (low-density polyethylene)

Prospects for expansion of research in the field of polyolefin synthesis (low-density polyethylene)

Constituents of cigarette smoke. XI. The isolation and synthesis of acenaphthylenes and macrocyclic polyolefins.

Acenaphthylene, the monomethylacenaphthylenes, and some dimethylacenaphthylenes have been identified in cigarette smoke condensate. Some of the acenaphthylenes were synthesised, as was also a perhydro-macrocycle (X). The possible formation of cromatic compounds from macrocyclic polyolefins is discussed, and the isolation of such a macrocycle from cigarette smoke is described. The mass spectra of some acenaphthylenes are described.