Solubility of P3HT in chloroform and chloroform:acetone mixtures: A spin-echo SANS study

• Solubility of widely used P3HT determined in chloroform and chloroform:acetone mixtures. • Neutron scattering spin-echo techniques allow the determination of solubility without additional processing steps. • Agrees with the Hansen solubility parameters and are consistent with acetone being more polar than both chloroform and P3HT. P3HT is a semiconducting polymer widely used in solution-processable photovoltaic research. Measuring the solubility of P3HT in organic solvents is usually an arduous and time-consuming process. Here we report the presence or absence of P3HT nanoparticle agglomeration in optically opaque solutions of P3HT, with concentrations ranging from 6.2 to 22.0 mg·mL −1 , in pure chloroform and in chloroform:acetone mixtures, using the neutron scattering technique, Spin-Echo Small Angle Neutron Scattering (SESANS). We demonstrate in-situ that the solubility of P3HT decreases from ∼ 22.0 mg/mL to < 6.2 mg/mL when the amount of acetone in solution increases from 0 vol% to 60 vol%. This work uses the ability of SESANS to probe P3HT nanoparticle aggregates, with dimensions ranging from ∼ 1 to several microns, in P3HT solutions with concentrations above the solubility limit.