Well-Defined Alternating Copolymers of Oligo(phenylenevinylene)s and Flexible Chains

A series of alternating copolymers containing oligomeric bis(2-ethylhexyl)-p-phenylenevinylene (BEH-PPV) chromophores and conformational-flexible n-decyl or tetraethylene glycol chains were prepared. The polymerization was carried out using Sonogashira coupling conditions between monomers composed of an iodo-terminated PPV oligomer (trimer, pentamer, or septamer) and a bis(phenylacetylene)containing flexible chain. Polymers containing the n-decyl chain attained higher molecular weights compared to the tetraethylene glycol-containing polymers. 4-Ethynylanisole-capped oligomers (trimer, pentamer, or septamer) were prepared, and their solution photophysical properties were compared to the analogous polymeric materials. The solution optical properties of the polymers were primarily determined by chromophore length of the constituent oligomers. In contrast, the thin film fluorescence spectra of the polymers showed substantial differences between n-decyl and tetraethylene glycol containing materials, suggesting significant changes in the degree of interchain coupling in the solid state. The control of effective conjugation length afforded by these materials makes them a promising system for understanding electronic trap states in conjugated polymers.