RAFT mediated polysaccharide copolymers

Reda Fleet, J.B. McLeary, V. Grumel, W.G. Weber, H. Matahwa, R.D. Sanderson
2008 European Polymer Journal  
ii Declaration I, the undersigned, hereby declare that the work contained in this thesis is my own original work and that I have not previously in its entirety or in part submitted it at any university for a degree. _____________________ Reda Fleet Abstract iii Abstract Cellulose, one of the most abundant organic substances on earth, is a linear polymer of D-glucose units joined through 1,4-β-linkages. Cellulose is however not easily processed without chemical modification. A number of
more » ... s exist for the modification of cellulose, of which the viscose process is one of the most widely applied. Grafting of synthetic polymeric chains onto or from cellulosic materials is an useful technique that can be used to combine the strengths of synthetic and natural polymers dramatically, so changing the properties of cellulosic materials (pulp, regenerated cellulose, cellulose derivatives). In this study five model xanthate (Reversible Addition-Fragmentation chain Transfer (RAFT)/Macromolecular Design through Interchange of Xanthates (MADIX)) agents, namely, monofunctional, difunctional, trifunctional and tetrafunctional species of the form S=C(O-Z)-S-R, with different leaving groups and different activating moieties, were prepared and then studied to determine the feasibility of cellulose modification via addition fragmentation processes. These agents were characterized by Nuclear Magnetic Resonance spectroscopy (NMR), Fourier Transform Infrared spectroscopy (FT-IR) and Ultraviolet spectroscopy (UV). Polyvinyl acetates (PVAc) in the form of linear, three armed and four armed star shaped polymers were then successfully synthesized in reactions mediated by these xanthate RAFT/MADIX agents Xanthates were applied to polysaccharide materials using the viscose process (xanthate esters were formed directly on a cellulosic substrate, with subsequent alkylation) Grafting reactions were then conducted with the polysaccharides; cellulose was modified with vinyl acetate, [this is an example of a surface modification of natural polymers that is of interest in various industries, such as textiles and paper manufacture]. Analysis of the graft copolymers was conducted via Size Exclusion Chromatography (SEC), Liquid Adsorption Chromatography (LAC), Thermogravimetric Analysis (TGA), and FT-IR. Polyvinyl acetate was successfully grafted onto three polysaccharides (cellulosic materials), namely Hydroxyl Propyl Cellulose (HPC), Methyl Cellulose (MC) and cellulose. The study showed that the modification of cellulosic substrates with defined grafts of vinyl acetate can be easily achieved through minor modifications to existing industrial techniques. Abstract iv Opsomming Sellulose, een van die volopste organiese verbindings ter wêreld, is 'n lineêre polimeer bestaande uit D-glukose eenhede, gekoppel deur 1,4-β-bindings. Sellulose is egter moeilik om te verwerk sonder chemiese verandering. 'n Aantal tegnieke is bekend vir die modifikasie van sellulose, waarvan die viskoseproses (Eng. viscose process) die algemeenste toegepas word. Enting (Eng. grafting) van sintetiese polimeerkettings aan, of van, sellulosemateriale is 'n toeganklike tegniek om die nuttige eienskappe van sintetiese en natuurlike polimere te kombineer, en gevolglik die eienskappe van sellulosemateriale te verander (b.v. pulp, geregenereerde sellulose, sellulose derivate). In hierdie studie is vyf model xantaat verbindings berei, as MADIX-tipe verbindings (Eng. Macromolecular Design through Interchange of Xanthates) vir RAFT (Eng. Reversible Addition-Fragmentation Chain Transfer) sinteses. Hierdie verbindings was monofunksionele, difunksionele, tri-funksionele en tetra-funksionele spesies van die vorm S=C(O-Z)-S-R, met verskillende verlatende groepe en verskillende aktiverende funksionele groepe. Die verbindings is gesintetiseer, gekarakteriseer en bestudeer, om die uitvoerbaarheid van sellulose modifikasie via die addisie-fragmentasie proses te bepaal. Hierdie verbindings is gekarakteriseerd m.b.v. KMR, FTIR en UV spektroskopie. Polivinielasetaat (PVAs) polimere, in die lineêre-, drie-arm en vierarm sterpolimere vorms is suksesvol gesintetiseer in hierdie xantaat RAFT/MADIXpolimerisasies. Xantate is met polisakkariede gereageer deur die gebruik van die viskose-proses (die xantaatesters is direk gekoppel aan 'n sellulosesubstraat, gevolg deur alkilering). Entingsreaksies is dan op die polisakkarides uitgevoer, om die modifikasie van sellulose met vinielasetaat te bewerkstellig. [Hierdie dien as 'n voorbeeld van 'n oppervlakmodifisering van natuurlike polimere wat van belang is in verskeie industrieë, b.v. tekstiele en papiervervaardiging.] Ontleding van die entkopolimere is gedoen m.b.v. grootte-uitsluitings-chromatografie (Eng. SEC), vloeistof-uitslui-tingschromatogafie (Eng. LAC), termogravimetrieseanalise (Eng. TGA) en Fouriertransformasie-infrarooispektroskopie (FTIR). Poliviniel asetaat (PVAs) is suksesvol geheg aan drie polisakkarides (sellulose materiale) naamlik, hidroksipropielsellulose, metielsellulose en sellulose. Die studie Abstract v toon dat die modifikasie van sellulosesubstrate met gedefinieerde enting van vinielasetaat maklik uitvoerbaar is deur wysiging van bestaande industriële tegnieke. Dedication vi Dedication I dedicate this work to my family and friends, and my beloved.
doi:10.1016/j.eurpolymj.2008.06.042 fatcat:jels4cubpjadhpip52i4tp5vsi