Field-flow fractionation of amphiphilic block copolymers

Journal Title
Journal ISSN
Volume Title
Stellenbosch : Stellenbosch University
ENGLISH ABSTRACT : Complex polymers have multiple distributions with respect to molecular weight, chemical composition, functionality as well as molecular topology and architecture. Moreover, these distributions affect polymer properties thus making it necessary to develop fractionation techniques capable of providing comprehensive information regarding these distributions. As a result, field-flow fractionation (FFF) has emerged as a main stream fractionation technique for the characterisation of complex macromolecular, colloidal and particulate materials as it has significant advantages over current column-based techniques. Of the various FFF subtechniques, thermal field-flow fractionation (ThFFF) shows sensitivity towards chemical composition and as such has successfully been applied to address the analytical challenges associated with chemical composition determination. The work presented in this study demonstrates that the separation capabilities of ThFFF are not limited to size and chemical composition, but can also be extended to include microstructure-based separations. It is further demonstrated that ThFFF is currently the only fractionation technique capable of separating dynamic polymer self-assemblies (such as micelles) according to corona microstructure while simultaneously providing information regarding shape, aggregation number, diffusion, thermal diffusion and Soret coefficients as well as size, molecular weight, chemical composition and their respective distributions. Moreover, the determination of chemical composition distributions was accomplished by a novel approach coupling ThFFF to FTIR via a LC-Transform interface.
AFRIKAANSE OPSOMMING : Komplekse polimere het verskeie verspreidings ten opsigte van molekulêre eienskappe, soos molekulêre massa, funksionaliteit, chemiese samestelling, mikrostruktuur, molekulêre argitektuur en molekulêre topologie. Hierdie verspreidings kan die toepassings van polimere direk beinvloed en dus is dit nodig om fraksioneringstegnieke te ontwikkel wat ‘n omvattende beeld van hierdie verspreidings kan lewer. As ‘n gevolg het veldvloeifraksionering (FFF) as ‘n hoofstroom polimeerkarakteriseringstegniek ontwikkel vir die analiese van makromolekulêre en partikulêre materiale omdat dit verskeie voordele het bo huidige metodes. Termiese veldvloeifraksionering (ThFFF) is n fraksioneringstegniek wat sensitief is vir die chemiese samestelling van polimeriese materiale en as sulks word dit gebruik om die uitdagings wat verband het met die bepaling van chemiese samestellings, aan te pak. Die werk wat hier beskryf word bewys dat die fraksioneringsvermoë van ThFFF is nie net beperk tot molekulêre groote en chemiese samestelling nie, maar dat dit ook mikrostruktuur insluit. Dit word ook gewys dat ThFFF is huidiglik die enigste fraksioneringstegniek wat die form, saampakgetal, diffusie, termies diffusie en Soret koëffisiënte asook molekulêre groote, molekulêre massa en chemiese samestelling verspreidings van micelles kan bepaal terwyl dit die hulle skei volgens chemiese samestelling. Die bepaling van chemiese samestelling verspreidings word gedoen deur n nuwe metode wat ThFFF koppel met FTIR deur gebruik te maak van n LC-Transform apparaat.
Thesis (PhD)--Stellenbosch University, 2016
Field-Flow Fractionation (FFF), Fourier transform infrared spectroscopy (FTIR), Block copolymers, Micelles, UCTD, Thermal field-flow fractionation (ThFFF)