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Influence of photochromic additives on the optical and electrical properties of polymer matrices
Tumová, Šárka ; Toman, Petr (referee) ; Weiter, Martin (advisor)
This thesis is focused on the photochromic molecule of spiropyran, which changes its structure as well as physical and chemical properties after UV irradiation. These changes are reversible, the molecule thermally restore its initial structure. For the study, the molecule SP1 with the systematic name 1',3'-dihydro-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-(2H)-indole] was used. This molecule was incorporated within polymers PVK, Tg PPV, PCBTDPP and PCDTBT and the method of UV-VIS spectroscopy was used to observe the photochromic activity within these matrices. The influence of matrices to the ability to undergo UV induced photochromic conversion as well as to the reverse conversion to the initial structure induced by heat was monitored. Furthermore, the influence of spiropyran to the electrical properties of individual matrices was studied. The effect of photochromic conversion to both, the mobility of charge carriers and to the photogeneration was observed. For this purpose, the method of current-voltage measurement was used.
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Characterization of cosmetic dispersion by centrifugal analyser
Tumová, Šárka ; Bokrová, Jitka (referee) ; Doskočil, Leoš (advisor)
Cosmetic products are widely used nowadays. These products are mostly emulsion systems, in which processes that lower physical stability can take place. This can leads among others to the shortening of the expiration date or to the reduction of the efficacy of the product. So, in the cosmetic practice, the physical stability is monitoring by tests. There are more types of these tests and they can be realized under different conditions. This Bachelor Thesis is focused on monitoring the physical stability of samples of cosmetics products by using an analytical centrifuge LUMiSizer and by using methods that are commonly used in a cosmetic practice and development. The aim of this study is to compare single results and to verify the suitability of the use of LUMiSizer for accelerated determine of the physical stability of cosmetic products. The stability of samples over time and the effect of the temperature on the stability of samples were monitoring by using the LUMiSizer device. Freeze-Thaw cycles and the conventional method of testing the stability of samples were applied as well. There was also determined the effectiveness of the stability test, mentioned by the literature, in this work. Based upon the results of experiments that were carried out and upon information given by manufacturers of samples that were used, the LUMiSizer device was evaluated as a useful tool for assessing the stability of samples although results obtained by the LUMiSizer device are not exactly the same as results of the conventional method. Although the application of additional methods is recommended.
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