Innovative spectroscopic and chromatographic techniques for the analysis of complex polyolefins prepared by metallocene catalysis

[摘要] ENGLISH ABSTRACT:The study focused on the analysis of a variety o f synthesised tailored copolymers.During the investigation o f the samples new and innovative analytical techniqueswere developed to be able to identify the presence of certain predicted or expectedcopolymerisation products.Emphasis was placed on the versatility of CRYSTAF as a method for the analysis ofsemi-crystalline copolymers. Changes in the crystallisation temperature were used asan indicator, while the type o f method, solvent and sample weight served as variablesin the system. The percentage comonomer content distribution for an unknownsample was determined from the standard curve plotted with the aid o f copolymerswith known comonomer content.Ethylene/higher a-olefin and propylene/higher a-olefm copolymers were synthesisedby means o f a metallocene precatalyst. In both cases, NMR spectroscopy, DSC, GPC,and CRYSTAF were used as analytical tools. In the ethylene series it was shown thatthe sample mixture was homogenous in the molar mass axis (GPC) but not in thechemical composition axis (CRYSTAF) regarding the comonomer content. For thepropylene series, an increase in stereoerrors was observed by NMR and this wascorrelated with crystallisation on heating a DSC for the range o f copolymers.In the case where ethylene/methyl methacrylate block copolymers were synthesisedusing metallocene precatalyst, novel detection and separation methods were used anddeveloped. This included the use o f CRYSTAF fitted with a carbonyl filter, hightemperature gradient HPLC and high temperature liquid chromatography undercritical conditions (LCCC). The last two techniques were the first where separationcould be achieved with samples only dissolving at high temperature. All previousmentioned techniques, as well as the coupling of FTIR to GPC and high temperaturegradient HPLC via LC-Transform revealed that the samples consisted o f varyingethylene and MMA block lengths.

[发布机构] Stellenbosch University