New synthetic and characterization strategies for polyolefins

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dc.contributor.advisor Raubenheimer, H.G.
dc.contributor.advisor Pasch, H.
dc.contributor.advisor Van Reenen, A.J. Luruli, Nyambeni
dc.contributor.other Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology. en 2012-07-12T07:49:25Z 2012-07-12T07:49:25Z 2007-03
dc.description Thesis (PhD)--University of Stellenbosch, 2006. en_ZA
dc.description.abstract ENGLISH ABSTRACT: Metalloxycarbene complexes [(CO)5M1=O(R)M2(Cl)L2] (M1 = Cr , W; M2 = Zr, Hf; L = Cp, Cp*) were synthesized from the reaction between anionic Fischer-type carbene complex salts [(CO)5M1=C(O)R][NEt4] and metallocene chlorides. The molecular and crystal structures of [(CO)5W=C(Me)OZr(Cp)2Cl], [(CO)5Cr=C(Me)OZr(Cp)2Cl] and [(CO)5W=C(Ph)OHf(Cl)Cp2] determined by X-ray methods, show a short Ccarbene-O and relatively long O-Zr and O-Hf separations. Metalloxycarbene complexes in the presence of MAO are active catalysts for homo- and copolymerization of -olefins and produce polymers with heterogeneous properties. 1-Pentene oligomers, homopolymers of ethylene and ethylene/1-pentene copolymers were successfully synthesized using metalloxycarbenes/MAO and the results obtained were critically compared with those synthesized with metallocene/MAO catalysts. The GC and GPC show that 1-pentene oligomers produced with both metalloxycarbenes and metallocenes catalysts range from simple dimers to more complicated high molecular weight (2 600 g/mol) products. The properties of polyethylene and ethylene/1-pentene copolymers were evaluated by, among others, GPC, SEC-FTIR, preparative molecular weight fractionation and HPer DSC. Generally the polymers obtained using metalloxycarbene/MAO catalysts have broad and bimodal molecular weight distributions. The copolymers have higher concentration of 1- pentene in the lower molecular weight fraction than those produced with metallocene/MAO as shown by SEC-FTIR. Consequently, HPer DSC shows a decrease of melting and crystallization temperature towards the low molecular weight fractions. en_ZA
dc.description.abstract AFRIKAANSE OPSOMMING: Metaaloksikarbeenkomplekse [(CO)5M1=C(R)OM2(Cl)L2] (M1 = Cr , W; M2 = Zr, Hf; L = Cp, Cp*] is gesintetiseer in die reaksie tussen anioniese Fischer-tipe karbeenkomplekssoute, [(CO)5M1=C(O)R][NEt4], en metalloseen dichloriedes. Die molekulêre- en kristalstrukture van [(CO)5W=C(Me)OZr(Cp)2Cl], [(CO)5Cr=C(Me)OZr(Cp)2Cl] en [(CO)5W=C(Ph)OHf(Cl)Cp2] bepaal deur X-straalkristallografiese metodes, toon die aanwesigheid van kort Ckarbeen-O- en relatief lang O-Zr- en O-Hf-bindings. Metaaloksikarbeenkomplekse, in die aanwesigheid van MAO, is aktiewe katalisatore vir die homo- en ko-polimerisering van α-olefiene en is verantwoordelik vir die vorming van polimere met heterogene eienskappe. 1-Penteen oligomere, homopolimere van etileen en etileen/1-penteen ko-polimere is suksesvol gesintetiseer met metaaloksikarbeenkomplekse/MAO en die resultate sodoende verkry, is krities vergelyk met produkte gesintetiseer vanuit metalloseen/MAO prekatalisatore. Die GC en GPC resultate toon dat die 1-penteen oligomere, geproduseer met beide metaaloksikarbeenkomplekse en metallosene, kan wissel van eenvoudige dimere tot meer komplekse, hoë molekulêre massa (2 600g/mol) produkte. Die polietileen en etileen/1- penteen ko-polimere is gekarakteriseer deur onder andere gevorderde, GPC, SEC-FTIR, preparatiewe molekulêre massa fraksionering en HPer DSC. In die algemeen het die polimere verkry met metaaloksikarbeen/MAO katalisatore, breë en bimodale molekulêre massaverspreidings. Die ko-polimere bevat hoër konsentrasies van 1-penteen in die lae molekulêre massa fraksie in vergelyking met dié gevorm vanuit metalloseen/MAO–gekataliseerde mengsels, soos aangedui deur SEC-FTIR-analise. HperDSC wys 'n verlaging in smelt- en kristallisasietemperature in die laer molekulêre massa fraksies. af
dc.format.extent xxvi, 187 leaves : ill.
dc.language.iso en_ZA en_ZA
dc.publisher Stellenbosch : Stellenbosch University
dc.subject Polyolefins -- Synthesis en_ZA
dc.subject Theses -- Polymer science en_ZA
dc.subject Dissertations -- Polymer science en_ZA
dc.title New synthetic and characterization strategies for polyolefins en_ZA
dc.type Thesis en_ZA
dc.rights.holder Stellenbosch University en_ZA
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