Control over the photophysical properties of nanoparticles of regioregular poly(3-octylthiophene) using various poor solvents

Abstract

© 2015 Elsevier B.V. All rights reserved. In this study, we demonstrate an ability to control the photophysical properties of nanoparticles of regioregular poly(3-octylthiophene) (rr-P3OT) by utilizing solvent-nonsolvent system. The strength of local polymer-solvent interactions is controlled by using hexane or hexanol as a poor solvent. We have found that the assembling of rr-P3OT chains in mixtures of toluene and these poor solvents results in the formation of nanoparticles with average diameter of about 35 nm. Interestingly, the use of hexane or hexanol as a poor solvent causes drastic variation of photophysical properties of the resultant nanoparticles. Their absorption spectra show quite different patterns. In addition, the photoluminescent (PL) peaks are detected at 565 nm and 645 nm in the systems of toluene/hexane and toluene/hexanol, respectively. Photoemission quantum efficiency of the nanoparticles also depends significantly on type of the poor solvents. We further demonstrate that the photophysical properties can be systematically controlled by using a series of linear alcohols as poor solvents. The increase of alcohol chain length causes the decrease of its polarity, which in turn improves the polymer-solvent interactions. In the system of toluene/decanol, PL spectrum of the nanoparticles covers relatively broad energy region, ranging from about 540 to 770 nm. Our study provides a simple method for preparation of rr-P3OT nanoparticles with controllable photophysical properties.