Synthesis and characterization of homo- and copolymers of a-olefins using metallocene catalysts

Luruli, Nyambeni (2002-03)

Thesis (MSc)--Stellenbosch University, 2002.


ENGLISH ABSTRACT: This study comprises the synthesis and characterization of propene/lower a-olefin copolymers and a-olefm homopolymers using metallocene catalyst systems. Incorporation of a-olefin comonomer into the polypropene backbone led to a change in properties such as microstructure and melting and crystallization temperatures. Synthesis of propene/a-olefin (J-butene, l-pentene, l-hexene and 4-menthyl-l-pentene) copolymers was carried out using the Me2Si(2-Methylbenz[e]indenyl)2ZrChIMAO catalyst combination. Copolymers were characterized by NMR, GPC, DSC and CRYSTAF. Comonomer incorporation was generally kept below 6 % to ensure crystallizable copolymers. Comonomer content influences tacticity. It was especially pronounced for propenell-butene copolymers and attributed to the formation of clusters. Melting and crystallization temperatures, (Tm (DSC), Tc (DSC) and Tc (CRYSTAF)), of propene/lower a-olefin copolymers decreased linearly with an increase in comonomer incorporation and strongly depend on comonomer type displaying a different behaviour compared to that of propene/ higher a-olefins (l-octene, I-decene, l-tetradecene, and 1- octadecene) copolymers. The melting and crystallization temperatures of propene/4- methyl-l-pentene copolymers occur between those ofpropene/l-pentene and propenellhexene. Poly-n-olefins (l-pentene, l-hexene, l-octene and l-decene) were prepared using a series of (R-115_C9H6)2ZrChIMAO[R = benzyl, phenyl and Si(CH3)3] and Me2C(115-C5H4-115- C9H6)ZrCh/MAO catalysts under different conditions. The resulting oligomers and polymers were characterized by GPC and NMR. Better conversions were obtained using catalysts with less bulky substituents and high MAO/catalyst ratios. Products ranged from dimeric oligomers to poly-u-olefins with molar masses between ca. 300 g.mol" and 6000 g.mol". Polydispersities, MwlMn, of poly-n-olefins synthesized at room temperatures were approximately 2, however, higher polydispersities were obtained at higher temperatures. Various end groups such as vinylidene, 1,2 disubstituted and 1,1,2 trisubstituted double bonds were observed and attributed to different propagation and termination reactions. The most important vinylidene end group corresponds to a specific 1,2 monomer insertion and termination by p-elimination.

AFRIKAANSE OPSOMMING: Hierdie studie behels die sintese en karakterisering van propeen/laer-a-olefien kopolimere en a-olefien homo-polimere wat berei is deur van metalloseen-katalisatore gebruik te maak. Die insluiting van 'n a-olefien ko-monomeer in die ruggraat van propileen het 'n verandering in eienskappe soos mikrostruktuur, smelting en die temperatuur van kristallisasie tot gevolg gehad. Die sintese van propeen/a-olefien (l-buteen, I-penteen, I-hekseen en 4-metiel-lpenteen) ko-polimere is uitgevoer met die katalisatorkombinasie Me2Si(2-Metielbenz[e] indeniel)2ZrClzIMAO. Daar is gepoog om die inkorporasie van die ko-monomeer tot <6% te beperk, om sodoende kristalliseerbare ko-polimere te verseker. Die komonomeerinhoud beïnvloed taktisiteit. Dit was veralopvallend in die propeen/l-buteen ko-polimere, en is toegeskryf aan die vorming van trosse (klusters) Die ko-polimere is gekarakteriseer deur van KMR, GPK, DSK en KRISTAF gebruik te maak. Die smelt-en kristallisasie-temperature (Tm (DSC), Tc (DSC) en Tc (CRYSTAF») van die propeen/Iaer-n-olefien ko-polimere het lineêr afgeneem met 'n toename in ko-monomeer inkorporasie en het sterk afgehang van van die tipe ko-monomeer. Die gedrag van laasgenoemde ko-polimere het verskil van dié van die propeenlhoër-a-olefien kopolimere (l-okteen, I-dekeen, I-tetradekeen, en l-oktadekeen). Die smelt- en kristallisasie-temperature van die propeen/4-metiel-l-penteen ko-polimere lê tussen dié van propeen/l-penteen en propeen/l-hekseen. Die poli-a-olefiene (l-penteen, I-hekseen,l-okteen en I-dekeen) is onder verskillende reaksiekondisies berei deur van die katalisatore (R-115-C9H6)zZrChIMAO [R=bensiel, feniel en Si(CH3)3] en Me2C(115-C514-115-C9H6)zrChIMAO.gebruik te maak. Die nuwe oligomere en polimere is met behulp van GPK en KMR gekarakteriseer. Katalisatore met kleiner substituente en hoër MAO/katalisator-verhoudings lewer beter omskakelings. Produkte het gevarieer vanaf dimeriese oligomere tot poli-a-olefiene met molêre massas tussen 300 en 6000 g.mol'. Die polidispersie van die poli-a-olefiene by kamertemperatuur gesintetiseer was ongeveer 2; hoër polidispersies is egter by hoër temperature verkry. Vinilideen, 1.2-disgesubstitueerde- en 1,1,2-trigesubsidueerde dubbelbindings is as eindgroepe waargeneem. Dit is toegeskryf aan verskillende voortplantings- en termineringsreaksies. Die belangrikste vinilideen-eindgroep stem ooreen met 'n spesifieke 1,2 monomeerinvoeging en terminering deur p-eliminasie.

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