Conjugated Polymer Nanoparticles of Poly(9,9-di-n-dodecylfluorene-2,7-diyl) and MEH-PPV: Photoluminescence Properties, β-phase Formation and Morphology.

Conjugated polymer nanoparticles (CPNs) demonstrate exceptional versatility as nanostructured materials with promising applications in optoelectronics, photonics, bio-imaging, biosensing, and nanomedicine. Additionally, their properties can be easily tailored for specific applications through the choice of the conjugated polymer and surface modification. In this study, CPNs were synthesized via the reprecipitation method, and their optical properties were investigated. The formation of CPNs was studied using the solvent tetrahydrofuran (THF) to investigate the influence of the polymers' concentration on the nanoparticles' production. CPNs were successfully synthesized using two polymers: PFD (Poly(9,9-di-n-dodecylfluorene-2,7-diyl)), which predominantly emits in the blue region, and MEH-PPV (Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]), which predominantly emits in the red region. Increasing the polymer concentration during synthesis affected the optical properties of the nanoparticles produced by enhancing energy transfers between intra/interchain of the polymers in the collapsed state and the CPNs of PFD with high concentrations exhibited new fluorescence emission peak related to β-phase formation. Moreover, the fluorescence quantum yield of CPNs of PFD increases with concentration while for CPN of MEH-PPV seems to saturate for higher concentrations. Interestingly, the hydrodynamic radius of the CPNs remained largely consistent regardless of concentration and the changes in the optical properties.