A UV/visible spectroscopic study of water‐soluble conjugated polyenes prepared via the ring‐opening metathesis polymerization reaction

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Abstract
A series of water‐soluble conjugated polyenes, based on the poly(furanylvinylene) structure, have been prepared from readily available starting materials using ring‐opening metathesis polymerization followed by dehydrogenation of the resulting polymer. 13C NMR analysis of the precursor polymers shows that the stereochemistry of the main‐chain double bonds varies from 93% trans to 10% trans and is retained in the water‐soluble derivatives, allowing different degrees of extended conjugation. This is reflected in the UV/vis spectra of the materials. The polymers may be cast into films from aqueous solution, and the UV/vis spectra exhibit vibrational fine structure indicative of conformational rigidity; significantly this fine structure is retained on redissolving the high‐trans but not the high‐cis films. The absorption maximum of the visible spectrum shows a stronger pH dependence in the high‐cis polymers than in the high‐trans, and this is interpreted in terms of the different modes of hydrogen bonding which cis and trans units can adopt.