Synthesis and morphological characterization of segmented and branched polydimethylsiloxane-polyester copolymers

Abduallah, Abduelmaged Basher Elmabrok (2010-03)

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010.

Thesis

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.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/4021
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