Abstract. This study focuses on detailed investigation of solvent effects on controlling photophysical properties of poly [2-methoxy,5-(2’-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) nanoparticles prepared by using reprecipitation techniques. In this work, the MEH-PPV polymer is dissolved in various solvents, including chlorobenzene (CRB), toluene (TOL) and pyridine (PYR). The polymers in solutions adopt different conformations (i.e. collapsed or extended coils), depending on local polymer-solvent interactions. The differences of chain conformations cause the variations of chain packing within the nanoparticles. The majority of nanoparticles exhibit diameter of about 65-70 nm. The photophysical properties of MEH-PPV nanoparticles varied with type of solvents. The absorption spectra of nanoparticles exhibit a broad pattern with a long red tail at about 550 nm, indicating the formation of inter-and/or intrachain aggregates within the nanoparticles. However, the nanoparticle from TOL system shows blueshift of λmax, corresponding to the decrease of conjugation length due to the existence of collapsed coil. The photoluminescence (PL) spectra of MEH-PPV nanoparticles show consistent result with the shift of λmax to about 590 nm and vibronic shoulder at about 640 nm. The PL patterns vary with the type of solvents. In addition, the PL patterns depend on the variations of excitation wavelengths. These discrepancies indicated the variation of chain conformation and degree of aggregation within the nanoparticles. Our results demonstrate the simple method to prepare the conjugated polymer nanoparticle with different photophysical properties by changing solvents.
Synthesis, Effect of Solvents on Electronic Absorption Spectra and Antimicrobial Activity of Some Histidine Complexes