Orientador: Watson Loh / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-19T04:42:09Z (GMT). No. of bitstreams: 1 Brinatti_Cesar_M.pdf: 6269984 bytes, checksum: 65e7cdbf89a7e16102822d62f57e20e9 (MD5) Previous issue date: 2011 / Resumo: As sulfobetaínas (SB) são uma classe de surfatantes zwitteriônicos. A presença de grupos carregados tanto positiva quanto negativamente na mesma molécula concede à sua cabeça polar uma hidrofilicidade intermediária entre surfatantes iônicos e não-iônicos. O estudo termodinâmico de associação da série homóloga de sulfobetaínas, bem como sua interação com polímeros iônicos e não-iônicos, foi feito utilizando a técnica de titulação calorimétrica isotérmica (ITC), em diferentes temperaturas. O aumento da temperatura leva a um valor mais negativo de energia livre de Gibbs de micelização DmicG, o que favorece a micelização. O termo entrópico TDmicS, embora sempre positivo, é o responsável pela micelização em baixas temperaturas. No entanto, com o aumento da temperatura este termo perde sua intensidade, enquanto o termo entálpico DmicHinverte seu sinal, de positivo para negativo, superando em intensidade o termo entrópico, sendo então o responsável pela micelização em temperaturas elevadas. No estudo de interação com polímeros não-iônicos, o poli (ácido acrílico), PAA, induziu a formação de agregados de unímeros de surfatantes em concentrações abaixo de sua cmc, enquanto o poli (óxido de propileno), PPO, foi incorporado às micelas. Em relação aos polímeros iônicos, o polímero catiônico cloreto de poli (dialildimetilamônio), PDADMAC, e o polímero aniônico poli (acrilato de sódio), PAA, não apresentaram interação alguma com a sulfobetaína. Apenas o polímero aniônico poli (4-estireno sulfonato de sódio), PSS, induziu a formação de agregados de unímeros de surfatante em concentrações muito abaixo da cmc. Esta indução deve-se à interação eletrostática entre o grupo sulfonato (-SO3) do PSS e o grupo amônio ( RNMe2X ) da SB, auxiliada pela presença do grupo hidrofóbico estireno do polímero, que é incorporado às micelas / Abstract: Sulfobetaines (SB) are a class of zwitterionic surfactants. The presence of groups both positively and negatively charged in the same molecule renders an intermediate hydrophilicity between ionic and nonionic surfactants. The self-assembly thermodynamic study of a homologous series of sulfobetaines, as well as its interaction with ionic and nonionic polymers, was performed by isothermal titration calorimetry (ITC), in different temperatures. The increase in temperature leads to a more negative value of the Gibbs free energy of micellization DmicG, which favors micellization. The entropic term TDmicS, although always positive, is the responsible for the micellization in lower temperatures. However, with the increase in temperature this term loses its intensity, while the enthalpic term DmicH changes its sign, from positive to negative, overcoming the entropic term in intensity, and therefore being the responsible for the micellization in higer temperatures. In the study of interaction with nonionic polymers, poly (acrylic acid), PAA, induced the formation of aggregates of surfactant monomers in concentrations below its cmc, while poly (propylene oxide), PPO, was incorporated to the micelles. Regarding ionic polymers, the cationic poly(diallyldimethylammonium chloride), PDADMAC, and the anionic polymer poly (sodium acrylate), PAA, didn't show any interaction with the sulfobetaine. Only the anionic polymer poly(sodium 4-styrenesulfonate), PSS, induced the formation of aggregates of surfactant monomers in concentrations well below its cmc. This induction is due to the electrostatic interaction between the sulfonate group (-SO3) from the PSS and the ammonium group (RNMe2X) from the SB, aided by the presence of the hydrophobic group styrene in the polymer, which is incorporated into the micelles / Mestrado / Físico-Química / Mestre em Química

Cellulose is the most abundant biopolymer on Earth as it is found in every plant cell wall; therefore, it represents one of the most promising natural resources for the fabrication of sustainable materials. In plants, cellulose is mainly used for structural integrity, however, some species organise cellulose in helicoidal nano-architectures generating strong iridescent colours. Recent research has shown that cellulose nanocrystals, CNCs, isolated from natural fibres, can spontaneously self-assemble into architectures that resemble the one producing colouration in plants. Therefore, CNCs are an ideal candidate for the development of new photonic materials that can find use to substitute conventional pigments, which are often harmful to humans and to the environment. However, various obstacles still prevent a widespread use of cellulose-based photonic structures. For instance, while the CNC films can display a wide range of colours, a precise control of the optical appearance is still difficult to achieve. The intrinsic low thermal stability and brittleness of cellulose-based films strongly limit their use as photonic pigments at the industrial scale. Moreover, it is challenging to integrate them into composites to obtain further functionality while preserving their optical response. In this thesis, I present a series of research contributions that make progress towards addressing these challenges. First, I use an external magnetic field to tune the CNC films scattering response. Then, I demonstrate how it is possible to tailor the optical appearance and the mechanical properties of the films as well as to enhance their functionality, by combining CNCs with other polymers. Finally, I study the thermal properties of CNC films to improve the retention of the helicoidal arrangement at high temperatures and to explore the potential use of this material in industrial fabrication processes, such as hot-melt extrusion.