Synthesis and investigation of smart nanoparticles

[摘要] ENGLISH ABSTRACT:The use of various 'smart materials' (briefly meaning materials that respond to a change intheir environment) is currently of interest to both academics and industry. The primary aim ofthe current study was to entrap photochromic (PC) dyes in miniemulsions, as a means toimprove their fatigue resistance, thus synthesizing smart nanoparticles. In the coatings industrythe use of aqueous systems is becoming a common requirement for health and environmentalreasons.Miniemulsion entrapment allows the direct dispersion of PC dyes into aqueous systems whileallowing for the opportunity to tailor-make the host matrix in order to obtain a suitable PCresponse and improved fatigue resistance.The optimal instrument set-up required to establish the PC response of films of the so-calledsmart nanoparticles (i.e. PC miniemulsions) was determined. A UV-Vis instrument with achip-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 adesign of experiments. A chromene and spironapthoxazine (SNO) PC dye were entrapped inthe BMA miniemulsion. A hindered amine light stabiliser (HALS) was also entrapped with theSNO dye in the BMA miniemulsion to further improve the fatigue resistance. The followingPC properties of the smart nanoparticles films were evaluated: colourability, thermal decayrate, half-life and fatigue resistance. To compare results with conventional systems, a BMAsolution polymer was prepared. The SNO dye and different concentrations of the HALS weremixed with the BMA solution polymer.In comparison to the SNO smart nanoparticles the chromene smart nanoparticles films hadlower colourability, but better fatigue resistance.Incorporating HALS at levels of 0.5–2% in the BMA miniemulsion with PC dye did not leadto any significant improvement in fatigue resistance, yet films of the BMA solution polymershowed some improvement.SNO dye incorporated at 1% gave similar colourability in both miniemulsion and in solutionpolymer, yet the fatigue resistance of the films of the PC miniemulsions was much better.

[发布机构] Stellenbosch University