Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / Thesis submitted in partial fulfillment of the requirements for the degree
of Master of Science (Polymer Science)
at University of Stellenbosch. / ENGLISH ABSTRACT: The preparation of poly(acrylonitrile/methyl acrylate) [poly(AN-co-MA)] copolymers and
poly(AN-co-MA)/clay nanocomposites, via emulsion polymerization, their characterisation,
and the relationships between their molecular structures and physical properties are described.
The copolymer composition was varied, and the properties of the products were analysed and
correlated to copolymer composition.
The free volume properties of the copolymer were dependent on the glass transition
temperature (Tg), which is dependant on the copolymer composition. The copolymer
crystallinity decreased with increasing MA content. The decrease in crystallinity and increase
in both o-Ps lifetime and o-Ps intensity with decreasing Tg was caused by the enhanced chain
mobility brought about by the incorporation of methyl acrylate.
The poly(acrylonitrile-co-methyl acrylate)/clay nanocomposites with 60% AN:40%
MA (mol:mol) ratio were prepared using montmorillonite clay modified via adsorption, using
2-acrylamido-2-methyl-1-propanesulphonic acid (AMPS), via in-situ intercalation
polymerization. The poly(AN-co-MA)/clay nanocomposites with different clay loadings
showed no difference in morphology. They exhibited improved thermomechanical properties
and higher thermal stability than the neat copolymers.
The melt rheology results of these nanocomposites showed an improved storage
modulus as well as increased shear thinning behaviour with increasing clay content. However,
the nanocomposites exhibited long-time relaxation behaviour and their chemical structures
evolved during analysis. This was attributed to cyclisation reactions taking place at the
temperature used during the oscillatory tests.
The sorption isotherms of water vapour in these nanocomposites followed a dualmode
sorption behaviour (BET type II mode). Hysteresis was observed in sorption/desorption
isotherms of these nanocomposites. The equilibrium water uptake was higher in the nanocomposites compared to the neat copolymers, and it increased with increasing clay
content, especially at high water activities (0.8).
Although diffusion and permeability decreased with increasing clay content the
solubility increased due to the hydrophilic nature of the clay. Despite the decrease in diffusion
and permeability parameters the free volume hole radius of the nanocomposites remained constant, but a slight decrease in free volume hole number was observed. / AFRIKAANSE OPSOMMING: Die bereiding van poli(akrilonitriel/metielakrilaat) [poli(AN-ko-MA)] kopolimere en
poli(AN-ko-MA)/klei nanosamestellings deur middel van emulsiepolimerisasie, hul
karakterisering asook die ooreenkoms tussen hul molekulêre strukture en fisiese eienskappe is
beskryf. Die kopolimeersamestelling is gevarieer, en eienskappe is geanaliseer en dan
gekorreleer met die kopolimeersamestelling.
Die vrye-volume eienskappe van die kopolimeer was afhanklik van die
glasoorgangstemperatuur (Tg) wat weer afhanklik is van die kopolimeersamestealling. Die
kristalliniteit van die kopolimeer het verminder met die hoeveelheid MA teenwoordig. Die
afname in kristalliniteit en toename in beide die o-Ps leeftyd en o-Ps intensiteit met afname in
Tg is veroorsaak deur die beter kettingbeweegbaarheid wat veroorsaak is deur die byvoeging
van metielakrilaat.
Die poli(akrilonitriel-ko-metielakrilaat)/klei nanosamestellings met 60% AN:40% MA
(mol:mol) verhouding is berei deur die gebruik van montmorillonietklei, gemodifiseer deur
die adsorpsie van 2-akrielamido-2-metiel-1-propaansulfoonsuur (AMPS) deur middel van 'n
in-situ interkaleringspolimerisasie. Die poli(AN-ko-MA)/klei nanosamestellings het, ten spyte
van die verskillende hoeveelhede klei wat gebruik is, geen verandering in morfologie getoon
nie. Hulle het wel beter termodinamiese eienskappe en hoër termiese stabiliteit as die
oorspronklike kopolimere getoon.
Die smeltreologie resultate van hierdie nanosamestellings het ‘n beter stoormodulus
getoon, sowel as toenemende skuifverdunningsgedrag met 'n verhoogde klei inhoud. Tog het
die nanosamestellings lang tyd-ontspanningsgedrag getoon en die chemiese struktuur het
verander tydens analise. Dit word toegeskryf aan die sikliese reaksies wat plaasvind by die
temperatuur wat gebruik is tydens die ossillatoriese toetse.
Die sorpsie isoterme van waterdamp in hierdie nanosamestellings het ‘n dubbel-styl
sorpsiegedrag gevolg (BET tipe II styl). Histerese is waargeneem in sorpsie/desorpsie isoterme van hierdie nanosamestellings. Die ewewig in wateropname van die
nanosamestellings was hoër as vir dié van die oorspronklike kopolimere en dit het toegeneem
met 'n toenemende klei inhoud, veral by hoë humiditeit (0.8).
Al het die diffusie en deurlaatbaarheid afgeneem met 'n toename in die klei inhoud,
het die oplosbaarheid toegeneem as gevolg van die hidrofiliese karakter van die klei. Ten
spyte van die afname in diffusie en deurlaatbaarheidsparameters, het die radius van die vryevolume
openinge van die nanosamestellings konstant gebly, maar ‘n klein afname in die aantal vrye-volume openinge is gevind.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4824 |
| Date | 12 1900 |
| Creators | Zengeni, Eddson |
| Contributors | Hartmann, P. C., Sanderson, R. D., University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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