Colloids Polymers and Surfaces

Research Interests

We are interested in surface/interface phenomena. At a colloidal or polymeric level, and within the broad field of colloid and surface chemistry,research is largely concentrated on the surfactant self-assembly, with or without the presence of polymers (or proteins), developing solutions of tunable rheology, from gels to mesomorphic or smectic phases. Other studies involve the pH definition near the colloid interfaces and the permeation through the soft interfaces developed.

From the biochemical/biomedical point of view, we have been working with polymeric matrices, namely hydrogels (entangled or cross-linked networks of polymer-based structure with swelling and entrapment capabilities) which possess a high potential for biomedical-oriented applications. In this regard we have been developing matrices for drug delivery systems for the skin barrier and we have been focus on allergy, burn and pain treatments. These matrices are based upon crosslinked gels from chitosan and dextran (polysaccharides) due to their biocompatibility and biodegradability. After the drug is incorporated studies on the stability of the formulation and the release properties of the drugs are modeled.

Another multidisciplinary topic being covered is the extraction and identifi cation of surface active agents from plant origin, including polyphenol families with antioxidant capabilities. Presently, most of our studies in this fi eld are dealing with the cork tree, coffee and some Portuguese varieties of beans. From the more environmental oriented point of view we have been working with the “green solvents” known as Room Temperature Ionic Liquids (RTIL) dispersed in bulky aqueous and non-aqueous solvents. Some of the studied RTIL’s, when dispersed in aqueous solutions, act as a new class of surfactants with unique abilities because along with the highly advantageous characteristic of these “green fluids” as bulk solvents, they can be nano-dispersed in water and some non-aqueous solvents. Here, one can combine two reagents of completely different natures (hydrophilic and hydrophobic) into a macroscopically homogeneous solution, being micellar or microemulsion states. Some very recent preliminary results suggest that in equimolar mixtures of SDS and long hydrocarbon chain RTIL’s, both mixed micelle behaviour and catalytic effects are present. These phenomena are currently under a deeper investigation.
 

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Selected Publications

1. M. Blesic, A. Lopes, E. Melo, Z. Petrovski, N. Plechkova, J. Lopes, K. Seddon, L. Rebelo, On the Self-Aggregation and Fluorescence Quenching Aptitude of Surfactant Ionic Liquids, J. Phys. Chem. B, 112 (2008), 8645–8650
2. A. Lopes, K. Edwards, E. Feitosa, Extruded vesicles of dioctadecyldimethylammonium bromide and chloride investigated by light scattering and cryogenic transmission electron microscopy, J. Colloid Interf. Sci., 322 (2008), 582-588
3. Lameiro M. H., Lopes A., Martins L. O., Alves P. M. and Melo E. (2006). “Incorporation of a model protein into chitosan-bile salt microparticles.” International Journal of Pharmaceutics 312(1-2): 119-130