This paper reports a polythiophene derivative that contains oligo(ethylene oxide) short side chains

poly(3-oligo(ethylene oxide)3-thiophene) (P3OET) of Mn 6000

which is synthesized by nickel-catalyzed polymerization of 2-bromo-5-iodine-3-oligo(ethylene oxide)3-thiophene.The presented P3OET can well dissolve in tetrahydrofuran

a good solvent

and emit orange-colored light under UV illumination at room temperature.In water

a selective polar solvent of P3OET

P3OET self-assembled into spherical nanostructures that showed a red-colored emission with a red-shifted spectrum and decreased quantum yield

in comparison with that in tetrahydrofuran; in contrast

in methanol

another selective polar solvent of P3OET

P3OET self-assembled into silk-like nanostructures that showed a yellow-colored emission with a blue-shifted spectrum and enhanced quantum yield

which is a quite unusual phenomenon that is also called aggregation-enhanced emission.Moreover

the integration of oligo(ethylene oxide) and polythiophenes made the presented P3OET exhibit temperature responsive behavior in aqueous solutions

similar to that of the temperature responsive polymers of oligo(ethylene glycol) methacrylate reported previously in literatures.This unique property of oligo(ethylene oxide)-contained polymers resulted in reversible temperature-induced twisting of the polythiophene conjugated backbone

allowing the reversible varying on the conjugation length by changing the temperature in milieu

which was accompanied by pronounced spectroscopic changes.At elevated temperatures

the blue-shifted spectra with enhanced intensities were recorded in aqueous solutions.These unique features of P3OET make it possess great potential for chemo-/bio-detection applications.With mouse melanoma B16F10 cells as the model

the experimental results indicate that the P3OET assemblies can enter the cells and readily emit strong visible fluorescence for cellular imaging.The temperature responsive behavior of P3OET also allow manipulate the fluorescence intensity for sensing the cellular temperature change.The cellular temperature change can be induced by both the heat generated by an external heater and the intracellular temperature variations induced by external chemical stimuli

e.g.

adding carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone

an uncoupler of oxidative phosphorylation in mitochondria that can cause heat production by respiration

or adding 5-fluorouracil

an anticancer drug that can also induce an unveiled temperature variation due to early responses of apoptosis such as DNA cleavage.