Current Scientific Interests
Room Temperature Ionic Liquids (RTILs)
Room temperature ionic liquids (RTIL) are presently attracting a great attention as potential replacement of many noxious compounds for a wide range of activities, including (bio-)catalysis, electro chemistry, separation et cetera. Their success relies on the easy modulation of their performances upon slight changes in their chemical architecture, and that led to the introduction of the term "designer solvents" to characterize this fundamental feature of RTILs.
The research programme of our group focuses on the three main topic:
• Study of the morphology of the neat RTILs and their binary mixures (with water, alcohol etc.) by means of complementary X-Ray and Neutron Wide and Small Angle Scattering. The experimental data are collected on EDXD home Facilities, at Synchrotrons (ESRF, Elettra), and at Neutron Scattering Facilities (ILL, BENSC, ISIS).
• Study of the microsopic dynamics of neat RTILs by using light , neutron and X-ray scattering, dielectric and Raman spectroscopy. The complementarity of the techniques allows the access to a wide dynamic and spatial window to probe relaxation phenomenon. The dynamical properties are investigated under variation of several parameters (alkyl chain length, anion type, additive concentration, etc.)
• Computational rationalization of the (structural and dynamic) experimental data by means of suitable molecular dynamics simulations, after force field parametrization with the data themselves and the results of high-level ab initio calculations.
RTILs are novel solvents that are used in the framework of green chemistry and are finding many smart applications in synthesis, catalysis, chemical engineering etc.
Using high resolution QENS (t.o.f. and backscattering) and NSE techniques we are developing a research program on the complex relaxation behaviour of these materials, thus achieving a world leadership in this field.
Using diffraction techniques (both neutron and X-ray diffraction) we recently provided the first experimental evidences of the existence of nanoscale structural organization in neat RTILs. This observation represents a breakthrough in the rationalisation of the intriguing chemical-physical properties of this important class of green chemicals. The activity at Large Scale Facilities is of excellence, as indicated by the recent highlights: (ELETTRA Synchrotron Highlight: http://www.elettra.trieste.it/ science/highlights/2001-2002/elettra_highlights_2001-2002-pg054.pdf ed NMI3 Highlight: http://neutron.neutron-eu.net/n_nmi3/n_access_activities/1580).
These results have been the topic for invited plenary talk at the Meeting on Relaxation in Complex Systems (Rome (ITA), September 2009) and at the Conference on Ionic Liquids (Yokohama (JP), august 2007). The NSE/backscattering data obtained at different world facilities (HZB, NIST and ILL) will be presented at an invited talk at ACS Meeting in San Francisco in March 2010 (http://www.chemistry.bnl.gov /SciandTech/PRC /physchemil2010.html).
In the framework of FIRB-Futuro in Ricerca grant that I am going to coordinate in the period 2010-2013, several issues related to this theme will be addressed. The project involves tight interaction with two research groups at the Dept. of Chemistry of the Sapienza University in Rome and the Dept. of Chemistry at the Cagliari University.
The research focus will be on a rationalisation of structural (by X-ray and neutron scattering) and dynamic (by neutron, dielectric and Raman spectroscopies) properties of RTILs on the basis of Molecular Dynamics simulations. RTILs will be studied in a number of conditions, including neat state, binary mixtures (e.g. with water, other small molecular compounds, macromolecules etc. ), nano-confinement and mixtures with gases such as CO2 and CH4.
• Aggregation processes in supercritical CO2.
Supercritical (sc-) CO2 is attracting huge interest as a green solvent for many chemical processes, such as synthesis, separation, catalysis etc.
I am very active in characterising structural features of sc-CO2 solutions of block-copolymers, using neutron and X-ray diffraction. Using these techniques I provided the first description of the concept of Critical Micellization Density (cmd), rationalising the occurrence of aggregation processes when the solvent density crosses a critical value. The morphological properties of these systems were also investigated in terms of aggregates interacting through an hard sphere potential, providing an excellent description of combined neutron and X-ray diffraction data. Taking advantage of the high brilliance of synchrotron sources and using a home-developed high pressure cell I also characterised the kinetics of micelles formation and disruption in sc-CO2.
• Polymer Structure and Dynamics
I am active in characterizing morphology and relaxation processes in amorphous polymers across their glass transition. Much of the activity focused on atactic polypropylene (aPP). The morphology of aPP has been studied using neutron diffraction on a fully deuterated sample. The development of intermediate range order correlation, which has a dynamic origin, has been observed [Highlight of the HZB Annual Report (2005)]. aPP was also investigated by means of neutron spectroscopy techniques (QENS and NSE), covering the dynamics from fraction of psec to tens of nsec. Using this approach the sub-Tg dynamics in aPP was accessed, successfully comparing with Molecular Dynamics simulations.
In order to access the collective dynamics in aPP, a deuterated sample was characterised with NSE over an unprecedently large dynamic window of five decades in time, providing high quality data which allow strict testing of theories (e.g. Mode Coupling Theory) on glass transition features. This is the only existing data set where data over such a wide dynamic range are collected at the same spectrometer without any arbitrary data treatment. Such a result was achieved through the optimization of the NSE setup at SPAN (HMI), in which I was directly involved.