Electrochemical and optical properties of amorphous segmented conjugated polymers

MARCELA F. ALMASSIO; PABLO G. DEL ROSSO; GABRIEL PLANES; CESAR BARBERO; RAÚL O. GARAY

Buenos Aires-Argentina

Simposio; 15th International Symposium on Metaestable, Amorphous and Nanostructured Materials; 2008

ISMANAM Steering Committee and International Advisory Board

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:PL; mso-fareast-language:PL;} @page Section1 {size:595.3pt 841.9pt; margin:70.85pt 70.85pt 70.85pt 70.85pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Conjugated polymers can exist in a large number of morphological organizations at the molecular and nanoscopic levels. Such organizations spring from the interrelation between the rigidity of the aromatic segments and the structural flexibility, conferred either conformationally or by saturated groups placed in the main chain [1]. On the other hand, amorphous molecular glasses is a new materials class characterized by their high density of active units, good processability and homogeneous properties [2]. Amorphous molecular materials represent an approach to solve the inconveniences that emerge from the crystallinity, extensive aggregation and morphological heterogeneity of conjugated polymers. However, polymeric systems have traditionally been associated with highly stable amorphous states under thermal stress, with mechanical properties that cannot be paralleled by molecular systems and with much lower diffusion mobilities in multilayer devices. We have previously reported a study on polymer Ia composed of methoxy-substituted p-terphenylene units showing how the chain configuration and molecular weight of the polymer influenced its processability, morphology and optical properties [3]. In this communication,  we will present the optical (UV-visible, fluorescence and fluorescence anisotropy spectroscopies) and electrochemical (cyclic voltammetry) characterizations of thin films of two novel polymers, Ib and IIc, along with those of the model compounds IIa-c. The molecular architecture constrains the chainless chromophores into bent and folded conformations producing highly soluble (> 10% w/w in CHCl3) and morphologically stable amorphous polymers with high Tgs (near 160 Cº). No distinct absorption or emission spectral signatures corresponding to either aggregates or excimers were detected in Ib-c even after long-term annealing. Film fluorescence anisotropies that ranged from 0.130 (IIa) to 0.351 (IIc) showed that bulk exciton mobilities in these disordered assemblies are very sensitive to small structural changes in the chromophore periphery. Their electrochemical behavior parallels the fundamental characteristics observed in films of the model compounds IIa-c. References: [1]  P. Wood, I.D.W. Samuel, G.R. Webster, P.L. Burn,. Synt. Met. 119 (2001)571. [2]  Y. Shirota, J. Mater. Chem. 15(2005)75. [3]  P.G. Del Rosso, M.F. Almassio, P. Aramendía, S.S. Antollini, R.O. Garay, Eur. Polym. J., 43 (2007) 2584.