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Master's Dissertation
DOI
Document
Author
Full name
Talita de Francesco Calheiros
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2019
Supervisor
Committee
Petri, Denise Freitas Siqueira (President)
Barbosa, Leandro Ramos Souza
Loh, Watson
Title in Portuguese
Síntese e caracterização de nanopartículas poliméricas com cafeína
Keywords in Portuguese
Atividade fungicida
Cafeína
Estabilidade coloidal
Poli(Metacrilato de metila)
Poliestireno
Polimerização em emulsão
Abstract in Portuguese
Este trabalho consiste na síntese de nanopartículas poliméricas, de poliestireno (PS) e poli (metacrilato de metila) (PMMA) decoradas com cafeína, através de um processo de polimerização em emulsão utilizando-se dois tipos de surfactantes, um catiônico e outro aniônico, e cafeína. As soluções de surfactante com e sem cafeína foram caracterizadas por análises de tensão superficial e condutividade. As dispersões poliméricas foram caracterizadas por espalhamento de luz dinâmico, medidas de potencial-ζ e de estabilidade coloidal. Os polímeros foram caracterizados por calorimetria exploratória diferencial (DSC), espectroscopia vibracional no infravermelho no modo de refletância total atenuada (FTIR-ATR), microscopia de força atômica (AFM) e microscopia eletrônica de transmissão (TEM). Além disso, foram realizadas sínteses dos mesmos polímeros na ausência de surfactante com e sem cafeína, para melhor compreensão de sua influência no meio. Essas sínteses foram caracterizadas por espalhamento de luz, DSC, FTIR-ATR e TEM. Filmes obtidos a partir das dispersões poliméricas foram analisados quanto ao brilho e quanto a ação da cafeína contra Candida albicans. De modo geral, a presença da cafeína não influenciou a morfologia ou a estabilidade coloidal das nanopartículas poliméricas. Porém, o sistema CTAB/cafeína e partículas de PMMA, sintetizadas no mesmo, mostraram comportamento e características diferenciadas. Medidas de condutividade e tensão superficial evidenciaram interações entre cafeína e CTAB. Bandas características de cafeína foram observadas em espectros de FTIR-ATR obtidos para partículas dialisadas de PMMA/CTAB/cafeína. A temperatura de transição vítrea (Tg) determinada para PMMA/CTAB/cafeína foi 12 °C menor que a Tg determinada para PMMA/CTAB. Estes resultados indicam interações específicas entre CTAB e cafeína do tipo cátion-π. Em dispersões e em filmes, a cafeína mostrou forte potencial fungicida. A cafeína se mostrou capaz de mudar o arranjo das partículas nos filmes deixando-os mais homogêneos e com maior brilho. Portanto, a cafeína se mostrou um aditivo muitointeressante para síntese de dispersões poliméricas e para formação de revestimentos que requerem alto brilho e propriedade fungicida.
Title in English
Synthesis and characterization of polymeric nanoparticles decorated with caffeine
Keywords in English
Caffeine
Colloidal stability
Emulsion polymerization
Fungicidal activity
Poly(Methyl methacrylate)
Polymers
Polystyrene
Abstract in English
This work focuses on the synthesis of polystyrene (PS) and poly (methyl methacrylate) (PMMA) nanoparticles decorated with caffeine, through an emulsion polymerization process, using cationic and anionic surfactants and caffeine. Surfactant solutions with and without caffeine were characterized by surface tension and conductivity analysis. Dispersions were characterized by colloidal stability and light scattering for obtaining zeta-potential, mean particle diameter and molar mass. Polymers were characterized by differential scanning calorimetry (DSC) for obtaining glass transition temperature (Tg), infrared spectroscopy (FTIR-ATR), atomic force microscopy (AFM) and transmission electronic microscopy (TEM). Also, synthesis of the same polymers without surfactants, in the absence and in the presence of caffeine, were performed, for better understanding its influence in the system. These syntheses were characterized by light scattering, DSC, FTIR-ATR and TEM. Finally, polymeric films were made in order to evaluate their brightness and fungicidal effect of caffeine. In general, the presence of caffeine did not influence the morphology or colloidal stability of polymer nanoparticles. However, the CTAB/caffeine system and PMMA particles, synthesized therein, showed particular behavior and characteristics. Conductivity and surface tension measurements showed interactions between caffeine and CTAB. Caffeine characteristic bands were observed in FTIR-ATR spectra obtained for dialysed PMMA/CTAB/caffeine particles. The glass transition temperature (Tg) determined for PMMA/CTAB/caffeine was 12 °C lower than the Tg determined for PMMA/CTAB. These results indicated cation-π interactions between CTAB and caffeine. In dispersions and films, caffeine showed strong fungicidal potential. The caffeine was able to change the arrangement of the particles in the films, making them more homogeneous and with greater gloss. Therefore, caffeine has proved to be a very interesting additive for the synthesis of polymer dispersions and for the formation of coatings that require high gloss and fungicidal properties.
 
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Publishing Date
2019-11-14
 
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