Data: 30 de janeiro
Título: "Supramolecular surfactant-cyclodextrin interactions".
Prof. Dr. Artur José Monteiro Valente, Universidade de Coimbra, Portugal.
Resumo: Cyclodextrins are able to act as host molecules in supramolecular chemistry with applications ranging from pharmaceutics to detergency. Among guest molecules surfactants play an important role with both fundamental and practical applications. The formation of cyclodextrin/surfactant host-guest compounds leads to an increase in the critical micelle concentration and in the solubility of surfactants. The possibility of changing the balance between several intermolecular forces, and thus allowing the study of, e.g., dehydration and steric hindrance effects upon association, makes surfactants ideal guest molecules for fundamental studies. Therefore, these systems allow for obtaining a deep insight into the host-guest association mechanism. Here, we review the influence on the thermodynamic properties of CD-surfactant association by highlighting the effect of different surfactant architectures (in particular, single tail, gemini and bolaform), with special emphasis on cationic surfactants. The applied methods for computation of the association stoichiometry and stability constants are also reviewed and discussed; this is an important point since there are significant discrepancies and scattered data for similar systems in the literature. In general, the surfactant-cyclodextrin association is treated without reference to the kinetics of the process. However, there are several examples where the kinetics of the process can be investigated, in particular those where volumes of the CD cavity and surfactant (either the tail or in special cases the head group) are similar in magnitude. This will also be discussed.
Docente responsável: Watson Loh
Data: 02 de fevereiro
Título: “Cellulose Nanocrystal-a promising sustainable nanomaterial for environmental applications”.
Prof. Dr. Michael K.C. Tam, University of Waterloo, Canada.
Abstract: Cellulose nanocrystals (CNCs) are rod-like nanoparticles obtained by sulfuric acid hydrolysis of cellulose fibres. Several properties of CNCs, such as its availability, low cost, high mechanical strength, large number of surface functional groups, high surface area per volume and aspect-ratio have led to an increasing interest in using them for adsorption and controlled release applications. Pristine CNCs were incorporated into hydrogel beads in order to eliminate the need for centrifugation. CNCs used in these hydrogel beads were also functionalized and such effects on the adsorption and controlled release characteristics were examined. Preliminary results suggested that CNCs incorporated alginate hydrogel bead systems possessed attractive adsorption properties both in batch and fixed bed column adsorption systems. These hydrogel beads could be regenerated and reused if necessary. Such sustainable nanomaterials possess attractive characteristics for the removal of various types of contaminants in waste water systems.
Docente responsável: Watson Loh.