Structural Study of the Thermochromic Transition in Poly(2,5-dialkyl-p-phenyleneethynylene)s

• Published in: Macromolecules Vol. 38; no. 23; pp. 9631 - 9637
• Main Authors: Lebouch, Nolwenn, Garreau, Sébastien, Louarn, Guy, Belletête, Michel, Durocher, Gilles, Leclerc, Mario
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-11-2005
• Subjects: Applied sciences; Electrical, magnetic and optical properties; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Solvent effect; Solvatochromism; Experimental study; Absorption spectrum; Thermochromism; Solid state; Conjugated polymer; Mixed solvent; Phenylene derivative polymer; Polyynic compound; Phenyleneethynylene derivative polymer; Optical properties; Ultraviolet visible spectrum
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma051342y

The solvatochromic and thermochromic properties of poly(2,5-di-2‘-ethylhexyl-p-phenyleneethynylene) have been investigated. While some important changes were observed in UV−vis absorption, calorimetric, and X-ray measurements, temperature-dependent FTIR, Raman, and solid-state NMR spectra did not reveal any significant shift of the peaks associated with the polymer backbone. These results suggest that the chromic effects are not mainly governed by conformational changes of the polymer. From these data and ab initio calculations performed on model compounds, it is believed that the thermochromic transition proceeds from aggregated polymers at room temperature to “free” (weakly interacting) polymer chains at higher temperatures.