Characterization of Organic Materials by High Temperature X-Ray Techniques

PIOTTO, A. T.; AVALOS, M. C.; BOLMARO, R. E.

Madrid

Congreso; XXII International Congress and General Assembly; 2011

International Union of Crystallography

Characterization of Organic Materials by High Temperature  X-Ray Techniques. Ana T. Piotto,a Raúl E. Bolmaro,a Martina C. Avalos.b  aCondensed Matter Group, Instituto de Física Rosario, (Rosario, Argentine). bPhysical Metallurgy Group, Instituto de Física Rosario, (Rosario, Argentine). E-mail: piottoana@gmail.com In the field of materials science, the study of properties of materials constituted by organic macromolecular systems with p-extended conjugation is an area of great interest. This type of compounds exhibits remarkable electro-conductive, optical and magnetic properties as shown for instance by fluorene derivatives (1), obtained by chemical synthesis [[1]]. This class of materials is particularly important in artificial photosynthesis, photocatalysis, solar cells, molecular computing and optoelectronics. [[2]] High Temperature Powder X-Ray Diffraction techniques (XRD) were used to explore in situ possible crystallinity changes in some of these compounds. XRD pattern analysis, allowed evaluating their response regarding chemical identity preservation in relation to their crystal structures in between room temperature and 400 °C. The experiments were performed under atmospheric conditions and temperatures fixed at 25 °C, 150 °C and 400 °C. At 25 °C they all showed crystallinity that was lost when temperatures reached 150 °C, where they all showed an amorphous character that remained unchanged at temperatures around 400 °C. (Graphic 1) We assume that this change can be related to a polymeric reaction, generated in situ at higher temperatures. [[3]] Those results were also investigated by using other analytical techniques like Differential Thermal analysis (DTA), Differential Scanning Calorimetry (DSC) and Mass Spectroscopy (MS). The results confirmed that the presumed occurrence of polymerization reactions is correct. The using of High temperature Powder XRD techniques, allowed us to explore changes in crystalline state of this organic materials. The application of these techniques will help us to investigate and understand the optical and electro -conductive properties of fluorene derivatives.  Keywords: X-Ray, high temperature, polymerization [[1]] A. Piotto, M. Avalos, R. Spanevello, XXVIII Congreso Argentino de Química. Universidad Nacional de Lanús, Argentina (September 2010). [[2]] N. Nielsen, F. Diederich, The Chemical Record 2002, 189-198. [[3]] S. Masashi, O. Naoya, S. Fumio, M. Toshio, Polymer Journal 2011, 43, 51–57.