We are familiar with polymer materials in all aspects of our everyday lives - but in future, polymers are set to be important materials for electronics and displays too. In order to make them work as efficiently as possible it is important to understand the nature of the quantum states of the electrons that emit light from the materials. For many purposes it would desirable if the materials could emit polarized light; this can be achieved by exploiting the intrinsic anisotropy of these electronic states. In a recent Advanced Materials publication, researchers from Franco Cacialli' s group in the LCN, in collaboration with colleagues from the University of Oxford and Lodz, have demonstrated extremely high polarized light emission (above 95%) using polymeric films that are oriented by drawing them out using a stretchable matrix.
The study revealed that certain water-soluble conjugated polymers, reach very high degrees of alignment in such stretched matrixes; moreover, this alignment survives even when the polymer molecule is encased in an insulating 'sheath' made of cyclodextrin molecules. This is remarkable because cyclodextrin encapsulation might have been expected to prevent the alignment, and it is significant because such sheathed conjugated polymers have other desirable properties, such as reduced losses by migration of energy onto other molecules.
This work has been published in Advanced Materials (F. Di Stasio et al, Adv. Mat., DOI: 10.1002/adma.201004356).
Journal link: http://onlinelibrary.wiley.com/doi/10.1002/adma.201004356/abstract
Figure 1 Pictures and photoluminescence spectra of a stretched film optically excited with UV light polarised perpendicular (left, dashed line) and parallel (right, solid line) to the stretching direction. The dashed spectrum has been magnified 50 times for clarity.