Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT:
Polydimethylsiloxane–polyester (PDMS-PES) copolymers produce materials which have
enhanced properties and take advantage of the unique properties of the two very dissimilar
components. The dissimilar nature of the components results in these types of materials
typically having complex morphologies in the solid state as a result of phase segregation.
When the polyester component is crystallisable, an even richer variation in morphology can
be expected. The chain structure of the copolymer in terms of the distribution of the various
segments along the chain and the variation in the composition also has a dramatic impact on
the solid state morphology. In this study, two different types of polyesters were used to
synthesise five series of PDMS-PES segmented copolymers and one series of PDMS-PES
branched copolymer. The two polyester segments selected were polybutyleneadipate (PBA)
and polybuthylenecyclohexancarboxylate (PBCH). The copolymers were synthesised via
polycondensation in the melt state. Insights on many variations in the PDMS-PES copolymer
synthesis are given. The copolymer series synthesized gave systematic series where the
influence of the polyester type, chain architecture, bulk composition, block length,
crystallinity and processing condition on the bulk and surface morphology could be studied.
The remarkable variations in the properties of the copolymer were attributed to the
differences in the copolymers morphology in terms of the microphase segregation,
crystallization and the free volume properties. These variations were also found to alter the
nature of the surface compositions and the related surface properties. Multiphase morphology
exhibited in all the PDMS-PES copolymers and the type of morphology observed was
dependent on PDMS contents, PDMS segment length and the degree of branching. Three
types of morphology were observed: spherical micro-domains of PDMS in a matrix of PES,
bicontinuous double diamond type morphology, and spherical micro-domains of PES in a
matrix of PDMS. Spherical domains of the PDMS were also observed for low PDMS content
copolymers between the crystalline polyester lamellae. The complexity of the PDMS-PBCH
copolymer morphology was further investigated, using an extensive set of experimental data
that has been drawn together with using positron annihilation lifetime spectroscopy (PALS)
and developing and applying a new type of hyphenated technique between fractionation
(chromatography) and microscopy (atomic force microscopy) techniques. The outcome has
provided a unique perspective regarding the complexity of the PDMS-PBCH copolymer
morphology, which is believed to provide basis for a theoretical structure-properties
relationship in this fascinating class of thermoplastic material. / AFRIKAANSE OPSOMMING:
Polidimetielsiloksaan–poliëster (PDMS–PES) kopolimere lewer verbindings met goeie
eienskappe en trek voordeel uit die unieke eienskappe van die twee baie verskillende
komponente. Aangesien die aard van hierdie twee verbindings baie verskil het hulle ‘n
gekompliseerde morfologie in die vastetoestand as gevolg van faseskeiding. Wanneer die
poliëster komponent kristalliseerbaar is kan ‘n nog ryker variasie in morfologie verwag word.
Die kettingstruktuur van die kopolimere in terme van die verspreiding van die verskillende
segmente al langs die ketting en die variasie in samestelling, het ook ‘n groot invloed op die
vastetoestandmorfologie. In hierdie studie is twee verskillende tipes poliëster gebruik om vyf
reekse PDMS–PES gesegmenteerde kopolimere en een reeks vertakte PDMS–PES
kopolimere te berei. Die twee poliëstersegmente is polibutileenadipaat (PBA) en
polibutileensikloheksaankarboksilaat (PBCH). Die kopolimere is berei deur middel van
polikondensasie in die smeltfase. Inligting aangaande verskeie faktore in the bereiding van
die PDMS–PES kopolimere is ingewin. Die reekse kopolimere wat berei is, het dit moontlik
gemaak om die invloed van die tipe poliëster, kettingargitektuur, grootmaatsamestelling,
bloklengte, kristalliniteit en reaksiekondisies op die oppervlakte en interne morfologie te
bestudeer. Die opmerklike verskille in the eienskappe van die kopolimere word toegeskryf
aan die verskille in die kopolimeermorfologie in terme van die mikrofaseskeiding,
kristalliniteit en vryevolume eienskappe. Hierdie verskille het ook veranderings in die
oppervlakte samestellings en verwante oppervlakte eienskappe teweeggebring. Multifase
morfologie, in alle PDMS–PES kopolimere en die tipe morfologie wat waargeneem is, is
afhanklik van die PDMS inhoud, die PDMS segmentlengte en die graad van vertakking. Drie
tipes morfologie is waargeneem: sferiese mikro-gebiede van PDMS in ‘n PES matriks, ‘n bikontinueerlike
dubbele-diamant tipe en sferiese mikro-gebiede van PES in ‘n PDMS matriks.
Sferiese gebiede van die PDMS is ook waargeneem in kopolimere met ‘n lae PDMS inhoud
tussen die kristallyne poliëster lae. Die kompleksiteit van die PDMS–PBCH
kopolimeermorfologie is verder ondersoek deur gebruik te maak van ‘n wye reeks
eksperimentele data afkomstig van positronvernietigingsleeftydspektroskopie (PALS), gevolg
deur die ontwikkeling en toepassing van ‘n nuwe soort gekoppelde tegniek – tussen
fraksionering (chromatografie) en mikroskopie (atoomkragmikroskopie) tegnieke. Die
resultate het ‘n unieke perspektief gegee wat betref die kompleksiteit van die PDMS–PBCH
kopolimeermorfologie en dien as ‘n basis vir die teoretiese struktuur–eienskapverwantskap
van hierdie interessante klas termoplastiese materiale.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4021 |
| Date | 03 1900 |
| Creators | Abduallah, Abduelmaged Basher Elmabrok |
| Contributors | Mallon, Peter, 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 | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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