Spectroscopic Study of Photophysical Change in Collapsed Coils of Conjugated Polymers:  Effects of Solvent and Temperature

Abstract

A relationship between conformation and photophysics of poly[2-methoxy-5-(2‘-ethylhexoxy)-p-phenylenevinylene] (MEH−PPV) in dilute solution was investigated by utilizing UV/vis absorption, excitation, and emission spectroscopy. By tuning polymer−solvent interactions, a control of conjugation length which relates to state of chain collapse is achieved. Position of absorption and emission spectra can be systematically moved within 60 nm by using a series of alcohols and aromatic solvents as well as mixed solvents. In addition to a decrease of conjugation length, the collapsed chain exhibit optical characteristics different from that of the extended counterpart. While a single type of emitter is present in the extended chain, separate emission from multiple emitters with various conjugation lengths is detected from the collapsed coils. Fluorescence decay measurements support the presence of multiple emitters. Studies of UV/vis absorption and photoluminescence upon increasing temperature detect a blue shift of transition energies and a decrease of absorption and emission efficiency. In addition, rate of the shift is found to decrease with increasing magnitude of chain collapse.

Ionizing radiation induced degradation of poly (2-methoxy-5-(2’-ethyl-hexyloxy) -1,4-phenylene vinylene) in solution

“…32 For MEH-PPV, especially, evidence shows that the polymer chains can be considered as a collection of approximately planar segments with different conjugation lengths, with an average of 10 repeating units. 33 Thus the CAFI study was performed using a MEH-PPV decamer.…”

Simple conjugated polymer nanoparticles as biological labels

“…This was caused by a spread in the individual chromophore conjugation lengths from coiling or twisting of the constituent polymer chains brought on by their transition from a solution to a particulate environment. With these different chromophores absorbing, a wider absorption profile is obtained, enveloping all those absorption bands (Traiphol et al 2006).…”

“…This delocalization enabled the formation of novel electronic species with lower band gaps. Although there might be coiling effects shortening effective conjugation length in the individual chains this is probably overcome by this orbital overlap during aggregation (Traiphol et al 2006).…”

Novel Polydiacetylene-Functionalized Nanostructures for Sensing Applications

“…Since the chemical nature of the chain terminal freely exposed to the outside seems to strongly influence the packing process of monomers around inorganic cores [10], we have undertaken the study of the photopolymerization behavior of differently double-functionalized diacetylenes (DAs) when arranged onto pre-formed silver nanoparticles with the aim of investigating the influence exerted by the tail groups on the optical properties of the PDA formed. To this purpose, monomers of general formula X-(CH 2 ) m -C≡C-C≡C-(CH 2 ) 8 -COOH, where X is a outer reactive group suitable for post-functionalization reactions and/or anchoring onto supports, have been synthesized and used.…”