Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Polymeric nanofibrous membranes that act as surfaces offer two compelling properties; they have extremely large surface areas that can be modified and they can offer multiple reactive sites depending on which polymer they were electrospun from. Combining nanofibrous surfaces such as these with photochromic dyes can give remarkable, light responsive materials. In this study, a terpolymer was electrospun and crosslinked (to impart insolubility to the material) to produce a nanofibrous mat that contained surface secondary-hydroxyl units and benzyl chloride units, from which monomers could grow using surface-initiated atom transfer polymerization (SI-ATRP). The surface was further fluorinated though the secondary-hydroxyl moieties to produce a hydrophobic crosslinked nanofibrous surface. n-Butyl acrylate and a photochromic spiropyran dye were copolymerized from the surface using SIATRP, in order to produce a surface that exhibited reversible adhesion towards a water droplet using ultraviolet and visible light as a stimulus to change between the two states. This in principle would allow the droplet to roll off and stick to the surface respectively. Although the surface displayed a colour change when switched, proving that the SI-ATRP had taken place, the droplet of water remained attached to the surface in both states. / AFRIKAANSE OPSOMMING: Polimeriese nanovesel membrane wat dien as oppervlaktes bied twee aantreklike eienskappe; hulle het baie groot oppervlakareas wat gemodifiseer kan word en hulle bied veelvuldige reaktiewe punte, afhangende van die polimeer waarvan hulle ge-elektrospin is. Deur sulke nanovesel oppervlaktes met fotochromiese kleurstowwe te kombineer, kan uitstekende lig reagerende materiale verkry word. In hierdie studie is ‘n terpolimeer ge-elektrospin en daarna gekruisbind (om die materiaal onoplosbaar te maak) om ‘n nanovesel web te kry wat oppervlak sekondêre-hidroksiel en benzielchloried eenhede bevat. Monomere kan dan vanaf hierdie eenhede groei deur middel van oppervlak-geïnisieerde atoomoordrag polimerisasie (OI-AOPR). Die oppervlak was verder gefluorineer via die sekondêre-hidroksiel eenhede om ‘n hidrofobiese, gekruisbinde nanovesel oppervlak te vorm. n-Butielakrilaat en ‘n fotochromiese spiropiraan kleurstof is gekopolimeriseer vanaf die oppervlak deur middel van OI-AORP om sodoende ‘n oppervlak te skep wat omkeerbare adhesie van ‘n water druppel gee as ultraviolet en sigbare lig as stimulus gebruik word om tussen die twee toestande te wissel. In beginsel sal die water druppel vanaf die oppervlak kan afrol én daaraan vassit, afhangende van die toestand van die oppervlak. Alhoewel die oppervlak van kleur verander het met die wisseling tussen die twee toestande, wat as bewys dien dat OI-AORP wel plaasgevind het, het die druppel water bly vassit aan die oppervlak in beide toestande.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The use of various ‘smart materials’ (briefly meaning materials that respond to a change in their environment) is currently of interest to both academics and industry. The primary aim of the current study was to entrap photochromic (PC) dyes in miniemulsions, as a means to improve their fatigue resistance, thus synthesizing smart nanoparticles. In the coatings industry the use of aqueous systems is becoming a common requirement for health and environmental reasons. Miniemulsion entrapment allows the direct dispersion of PC dyes into aqueous systems while allowing for the opportunity to tailor-make the host matrix in order to obtain a suitable PC response and improved fatigue resistance. The optimal instrument set-up required to establish the PC response of films of the so-called smart nanoparticles (i.e. PC miniemulsions) was determined. A UV-Vis instrument with a chip-type UV LED mounted inside for activation of the samples provided PC response results. A tungsten lamp with filter provided deactivation of the samples. A stable butyl methacrylate (BMA) miniemulsion formulation was established by conducting a design of experiments. A chromene and spironapthoxazine (SNO) PC dye were entrapped in the BMA miniemulsion. A hindered amine light stabiliser (HALS) was also entrapped with the SNO dye in the BMA miniemulsion to further improve the fatigue resistance. The following PC properties of the smart nanoparticles films were evaluated: colourability, thermal decay rate, half-life and fatigue resistance. To compare results with conventional systems, a BMA solution polymer was prepared. The SNO dye and different concentrations of the HALS were mixed with the BMA solution polymer. In comparison to the SNO smart nanoparticles the chromene smart nanoparticles films had lower colourability, but better fatigue resistance. Incorporating HALS at levels of 0.5–2% in the BMA miniemulsion with PC dye did not lead to any significant improvement in fatigue resistance, yet films of the BMA solution polymer showed some improvement. SNO dye incorporated at 1% gave similar colourability in both miniemulsion and in solution polymer, yet the fatigue resistance of the films of the PC miniemulsions was much better. / AFRIKAANSE OPSOMMING: Die gebruik van verskeie “slim materiale’ (kortliks beskryf as materiale wat reageer op `n verandering in hul omgewing) is tans van belang vir beide akademici en die industrie. Die hoofdoel van hierdie studie was om miniemulsietegnologie te gebruik om fotochromiese (FC) kleurstowwe vas te vang, vir die sintese van slim nanopartikels, om sodoende die weerstand teen afgematheid te verbeter. In die verfindustrie word die gebruik van waterbasissisteme meer algemeen weens gesondheids- en omgewingsredes. Die gebruik van miniemulsie sisteme om materiale vas te vang maak dit moontlik om FC kleurstowwe direk in waterbasissisteme te meng. Die sintese van `n unieke gasheer matriks word benodig om die optimum FC verandering te toon en weerstand teen afgematheid te verbeter. Om die FC verandering van die sogenaamde slim nanopartikel films (d.w.s. FC miniemulsies) te ondersoek was `n gepaste instrumentele opstelling nodig. Dit is vasgestel dat `n UV-Vis instrument waarin `n skyfie-tipe UV LED gemonteer is vir aktivering van die monsters, reproduseerbare resultate gegee het. Die monsters is gedeaktiveer deur gebruik te maak van `n tungsten lig met ‘n filter. `n Eksperimentele ontwerp is toegepas om `n stabiele butielmetakrielaat (BMA) miniemulsie formulasie te verkry. `n ‘Chromene’ en ‘spironapthoxazine’ (SNO) FC kleurstof is in die BMA miniemulsie vasgevang tesame met `n verhinderde amien ligstabiliseerder (VALS) om die weerstand teen afgematheid verder te verbeter. Die volgende FC eienskappe van die slim nanopartikels is gemeet: kleurintensiteit, tempo van termiese verwering, half-lewe en weerstand teen afgematheid. `n BMA polimeeroplossing is berei om resultate mee te vergelyk. Die SNO kleurstof en verskillende konsentrasies van die VALS is met die BMA polimeeroplossing gemeng. In vergelyking met die slim SNO nanopartikels het die intelligente chromene nanopartikelfilms `n swakker kleurintensiteit gehad, maar `n hoër weerstand teen afgematheid. Die gebruik van 0.5–2% VALS in die BMA miniemulsie met FC kleurstof het minimale verbetering in weerstand teen afgematheid getoon, maar daar was wel `n beduidende verbetering in die geval van films met FC kleurstof in `n BMA polimeeroplossing. Byvoeging van 1% SNO kleurstof in `n BMA miniemulsie of polimeeroplossing het dieselfde kleurintensiteit gelewer, maar die weerstand teen afgematheid van die FC miniemulsie was baie beter.