Nanochemistry through self-assembly : polymerisation of the organised phases of polyelectrolyte-surfactant complexes

[摘要] ENGLISH ABSTRACT:The general objective of this research was to develop a new approach to directtemplating, where the organised phases of polyelectrolyte-surfactantcomplexes are used as hosts for organic polymerisation reactions.The lamellar polyelectrolyte-surfmer complex of the tail-functionalised di(undecenyl) phosphate (roC11) and polydiallyldimethylammonium chloride(pDADMAC) was identified as a host for organic polymerisation reactions. Thecomplex showed higher stability (than the one found in the case of roC11 alone)when used as a template, owing to the presence of the polyelectrolytebackbone.The mobility of the reactive groups (positioned in the tails of the surfmer) wasnot sufficient for homopolymerisation reactions to take place. Direct, 1:1templating was only achieved on the incorporation of an unbound co-monomer(a dithiol) in the complex. Furthermore the thiol-ene polyaddition reaction usedoffered the advantage over conventional free radical polymerisation thatvolume shrinkage was largely avoided and possibilities for phase disruptionminimised. The pDADMA I roC11 complex was able to withstand swelling with-35 wt % of thiol co-monomer (constituting a 1:1 ratio of thiol to vinyl groups)without signs of phase disruption. The obtained polymer symplexes were curedcopies of the template proving that no phase disruption or disordering occurredduring the polyaddition. These results were confirmed using X-ray scatteringand microscopy. This is the first case of successful polyaddition within the organised phases ofpolyelectrolyte-surfactant complexes to be reported.The addition of a second co-monomer (a diene) to the reaction system provideda possibility by which to vary the composition of the novel composite materialsobtained through the ternary thiol-ene polyaddition within the complex. ittherefore allowed for the investigation of the effect of increasing the amount ofguest polymer on the structure of the host polyelectrolyte-surfactant complex.The increased d-spacing of the host structure with the increase in guestpolymer content gave the possibility to tune the material properties of thosehighly anisotropic networks. Onset of phase disruption was only observed with72 wt% copolymer included within the host. This unusually high degree ofswelling under preservation of nanoscale order could be attributed to theflexible, linear structure of the co-monomers used, since the addition of rigid comonomerswas reported to cause phase disruption at only - 17 wt% of swellingof the host polyelectrolyte-surfactant complex.' The high loading capability ofthe pDADMA I roC11 allowed for a large amount of otherwise unstructuredmaterial to be organised within the template.

[发布机构] Stellenbosch University