SL 10

optical Probes for acid-Base interactions in polymeric mIxtures

F. Böhme, U. Oertel, H. Komber

Leibniz Institute of Polymer Research Dresden, Hohe Straße 6, 01069 Dresden Boehme@ipfdd.de

Specific interactions in polymers, polymer blends, mixtures of polymers with low molecular weight compounds or polymeric composites may influence material properties significantly. This not only concerns mechanical and thermal performance, but also functional properties like optical behavior, conductivity or biological compatibility. Our special interest is focused on polymeric systems the optical properties of which are influenced by acid-base interactions between the components. We take advantage of alterations in optical properties occurring after deprotonation of chromophores ionically or covalently bound to a polymer. Examples of suitable structures are shown below.

Deprotonation strongly influences the electronic structure of the chromophores resulting in a distinct bathochromic shift of the chromophores longest wavelength absorption band by about 100 nm. Simultaneously, alterations in cis-trans isomerization and in non-linear optical behavior are observed.

In the examples introduced in the paper, polymers with pronounced basicity were used as proton acceptors. Among them are polyethylene imine and polyamidines with pK_a values up to 11. The interactions with the chromophores result into the formation of ionic complexes which also influence thermal properties and film forming behavior of the polymers beside the optical properties mentioned above.