We use molecular simulation and coarse grained techniques to obtain thermodynamic and transport properties of systems that are relevant for the chemical industry. In particular, we are interested in systems containing surfactants and liquid crystals, as well as fluids in confined systems, like gases and liquids in porous carbons, zeolites or related mesoporous materials.

Currently we are working on the following projects:

Hybrid porous materials (DeSANNS, FP6)

HOT PAPER

Dynamics of formation of porous materials (DeSANNS, FP6)

Surfactant-self assembly and the formation of porous materials (DeSANNS, FP6)

We are interested in understanding the formation of mesoporous solids where surfactant self assemblies are used as templates to direct the structure of the material. Such materials were first reported in the early 1990's by researchers in Mobil, and soon after several synthesis methods were reported using a variety of cationic, anionic, non-ionic surfactants or every block copolymers, to control the pore size and shape of the material.

Preliminary result allow us to understand the limitations for formation of ordered materials with hybrid precursors. Our current interest is to abandon the assumption that these systems are at equilibrium and study the effect of the extent of the silica condensation reaction upon the formation of ordered structures.

This figure contains several phase diagrams calculated using MC simulation of a model surfactant with different hybrid precursors. The work was done by A. Patti (URV, Spain) in collaboration with A.D. Mackie (URV, Spain).

Behaviour of surfactant self-assemblies

Solubilization and release of solutes from micelles has applications in many fields, including drug delivery, release of agrochemicals, personal care and other formulated products. We are using Dissipative Particle Dynamics to study the effect of the solvent in solutions containing triblock type surfactants. In particular we are interested in understanding the dynamics of the micelles when the solvent properties are suddenly changed.

Modelling Polymers of Intrinsic Microporosity in collaboration with P. Budd, Chemistry (U. Manchester), Coray Colina and Greg Larsen from Materials Science (Penn State)

Polymers of Intrinsic Microporosity (PIMs) are inherently porous solids due to their inability to pack efficiently as a consequence of having rigid and contorted monomers. The high microporosity of these materials makes them attractive for gas adsorption and storage. More importantly, the diversity of materials that can be obtained by changing the monomer structure can open the door to many application. The monomers for PIMs are synthesized by Neil McKeown (Cardiff University) and the polymers are prepared and characterised in P. Budd's lab at the University of Manchester. You can learn more about PIMs in P. Budd's webpage
Adsorption of CO2 on PIM -1.	We are generating molecular models for PIM structures to study their properties and potential applications. We use as starting information the structure of the monomer and the final density of the polymer. This allows us to generate a box (the one to the left is 1000 nm3). Using these models we can determine pore size distributions, pore connectivity and calculate adsorption properties with grand canonical Monte Carlo simulations.

Characterization of activated carbons

Activated carbons are probably the most widely used adsorbents, from industrial gas storage, to prevention of poison absorption by the gastrointestinal tract. Activated carbons are disordered materials, composed mainly of graphite platelets that can be stacked in different orientations. The distance between the platelets (pore size distribution), the presence of functional groups on the edges of these platelets (hydroxyl, carbonyl or carboxyl groups), and their distribution define their applications. Due to the high surface area of activated carbons, adsorption of different probe molecules is among the most important techniques used for its characterization. Unfortunately, interpretation of the experimentally measured data often requires the use of models that make important approximations (like the assumption of infinite slit pores) that may result in unrealistic descriptions of the material. More realistic descriptions of disordered carbonaceous materials have been recently obtained using molecular simulations [see for example, Pikunic, et al. Langmuir 2003, 19, 8586; Biggs, et al. Langmuir 2004, 20, 5786; Biggs and Buts Mol. Sim. 2006, 32, 579.].
We are generating models of activated carbons, using some experimental information (composition, density, etc.) as a starting point to generate a molecular level model of the carbon. These models are validated using calculated and experimentally measured adsorption isotherms.
This work is in collaboration of Dr. J. B. Parra's group at the Carbon Institute in Oviedo, Spain. Preliminary work on this area was funded by Lignocarb project.

Adsorption and transport in microporous materials (in collaboration with the IFP)