Salt-induced thermochromism of a conjugated polyelectrolyte

Peterhans, Lisa; Alloa, Elisa; Sheima, Yauhen; Vannay, Laurent; Leclerc, Mario; Corminboeuf, Clemence; Hayes, Sophia C.; Banerji, Natalie (2017). Salt-induced thermochromism of a conjugated polyelectrolyte. Physical Chemistry Chemical Physics, 19(42), pp. 28853-28866. Royal Society of Chemistry 10.1039/C7CP02734F

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We report here the photophysical properties of a water-soluble conjugated polythiophene with cationic side-chains. When dissolved in aqueous buffer solution (PBS, phosphate buffered saline), there is ordering of the polymer chains due to the presence of the salts, in contrast to pure water, where a random-coil conformation is adopted at room temperature. The ordering leads to a pronounced colour change of the solution (the absorption maximum shifts from 400 nm to 525 nm). Combining resonance Raman spectroscopy with density functional theory computations, we show a significant backbone planarization in the ordered phase. Moreover, the ratio of ordered phase to random-coil phase in PBS solution, as well as the extent of intermolecular interactions in the ordered phase, can be tuned by varying the temperature. Femtosecond transient absorption spectroscopy reveals that the excited-state behaviour of the polyelectrolyte is strongly affected by the degree of ordering. While triplet state formation is favoured in the random-coil chains, the ordered chains show a weak yield of polarons, related to interchain interactions. The investigated polyelectrolyte has been previously used as a biological DNA sensor, based on optical transduction when the conformation of the polyelectrolyte changes during assembly with the biomolecule. Therefore, our results, by correlating the photophysical properties of the polyelectrolyte to backbone and intermolecular conformation in a biologically relevant buffer, provide a significant step forward in understanding the mechanism of the biological sensing.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Departement of Chemistry and Biochemistry

UniBE Contributor:

Peterhans, Lisa Anna and Banerji, Natalie

Subjects:

500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry

ISSN:

1463-9076

Publisher:

Royal Society of Chemistry

Language:

English

Submitter:

Natalie Banerji

Date Deposited:

21 Nov 2018 13:58

Last Modified:

21 Nov 2018 13:58

Publisher DOI:

10.1039/C7CP02734F

BORIS DOI:

10.7892/boris.118313

URI:

https://boris.unibe.ch/id/eprint/118313

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