Synthesis and characterization of multiphase copolymers

Elhrari, Wael K. S. (2011-12)

Thesis (PhD)--Stellenbosch University, 2011.

Thesis

ENGLISH ABSTRACT: Multiphase copolymers generally consist of copolymers where the disparate natures of each of the segments results in complex phase-segregated morphologies in the solid state. The outstanding properties and wide range of applications of multiphase copolymers has led to the need for more sophisticated synthesis methods to produce copolymers with controlled structures. Associated with developments in synthetic methods is the need to develop suitable techniques to characterize these materials in order to obtain a better understanding of their structure–property relationships. The synthesis of multiphase copolymers presents many challenges. These are related to the nature of the molecular requirements, were the monomers of each of the different components may not be polymerized by all available polymerization techniques. This has led to the need to combine different polymerization techniques to overcome such limitations. The focus of this study is the combination of living controlled polymerization techniques, namely anionic polymerization and RAFT polymerization, with hydroboration/autoxidation, to produce non-polyolefin block and graft copolymers. Block copolymers were synthesized by coupling anionic polymerization and hydroboration/autoxidation reactions. The first block segment was prepared via anionic polymerization, and then end-functionalized with a suitable functional group (e.g. an allyl group). A hydroboration/autoxidation reaction was then used to initiate the polymerization of the second block by the slow addition of oxygen at room temperature. Graft copolymers were synthesized using the 'grafting from' technique, by coupling RAFT copolymerization with hydroboration/autoxidation reactions. The backbone polymer was synthesized via RAFT copolymerization of symmetric and asymmetric monomer, after which a hydroboration/autoxidation reaction was carried out to produce graft copolymers. The hydroboration/hydroxylation reaction could also be used to modify an unsaturated polymer chain. The EPDM rubber chain was modified by transforming the double bond into an hydroxyl group, which could undergo an esterification reaction with an acid chloride RAFT agent to produce the multifunctional RAFT polymer. This was used for the controlled living free radical polymerization of the graft chains. Significant amounts of homopolymerization in addition to graft formation were obtained. Solid state NMR (SS NMR) and positron annihilation lifetime spectroscopy were used to determine the compositional phase segregation point in the graft copolymers. The spin diffusion data from the SS NMR provided insight into the seemingly anomalous positron data at the phase segregation point. It is demonstrated how these two techniques can provide complimentary data on the solid state morphology of these multiphase materials.

AFRIKAANSE OPSOMMING: In die algemeen bestaan multifase kopolimere uit segmente van verskillende aard wat komplekse fase-geskeide-morfologie in die vastetoestand tot gevolg het. Die uitstekende eienskappe en wye reeks toepassings van multifase kopolimere het daartoe gelei dat meer gesofistikeerde sintesemetodes vir die bereiding van kopolimere met gekontrolleerde strukture nodig was. Gepaardgaande met verwante ontwikkelings op die gebied van sintesemetodes was dit nodig om gepaste analitiese tegnieke te ontwikkel vir die karakterisering van hierdie verbindings, ten einde die struktuur–eienskap verwantskap van hierdie materiale beter te verstaan. Daar is egter baie uitdagings m.b.t. die sintese van hierdie multifase kopolimere. Dit is afhanklik van die aard van die molekulêre vereistes waar die monomere van elk van die verskillende komponente nie deur alle beskikbare polimerisasietegnieke gepolimeriseer kan word nie. Dit het daartoe gelei dat verskillende polimerasietegnieke gekombineer is ten einde hierdie beperkinge te oorbrug. Die fokus van hierdie studie is die kombinering van lewende vry-radikaal gekontrolleerde polimerisasietegnieke, naamlik anioniese polimerisasie en RAFTpolimerisasie, met hidroborering/outoksidasie, om nie-olefiniese blok- en entkopolimere te berei. Blok-kopolimere is berei deur die koppeling van anioniese polimerisasie en hidroborering/outoksidasie reaksies. Die eerste bloksegment is berei via anioniese polimerisasie en daarna is endfunksionering met 'n geskikte funksionele groep (bv. 'n allielgroep) bewerkstellig. Daarna is 'n hidroborering/outoksidasie reaksie gebruik om die polimerisasie van die tweede blok te inisieer d.m.v. die stadige toevoeging van suurstof by kamertemperatuur. Entkopolimere is berei deur gebruik te maak van die 'ent-vanaf' tegniek, d.m.v. die koppeling van RAFT-kopolimerisasie met hidroborering/outoksidasie reaksies. Die rugraatpolimeer is berei d.m.v. kopolimerisasie van simmetriese en nie-simmetriese monomere waarna die hidroborering/outoksidasie reaksie uitgevoer is om sodoende entkopolimere te vorm. Die hidroborering/hidroksilasie reaksie kon ook gebruik word om 'n onversadigde polimeerketting te wysig. Die EPDM rubberketting is gewysig deur die omskakeling van die dubbelbinding in 'n hidroksielgroep, wat dan 'n esterifikasie reaskie kon ondergaan met 'n suurchloried-RAFT verbinding, om sodoende die multifunksionele RAFT-polimeer te vorm. Dit is gebruik vir die gekontrolleerde lewende vry-radikaalpolimerisasie van die entkettings. Behalwe entvorming is 'n hoë mate van homopolimerisasie waargeneem. Vastetoestand KMR (VS KMR) en positronvernietigingsleeftydspektroskopie is gebruik om die saamgestelde faseskeidingspunt in die entkopolimere te bepaal. Die spindifffusie data van VS KMR het insig verleen aan die oënskynlik onreëlmatige positrondata by die faseskeidingspunt. In die studie is bewys hoe hierdie twee tegnieke komplimentêre data kan lewer m.b.t. die vastetoestandmorfologie van hierdie multifase materiale.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/18003
This item appears in the following collections: