Visualizing spontaneous physisorption of non-charged π-conjugated polymers onto neutral surfaces of spherical silica in nonpolar solvents

Three non-charged π-conjugative polymeric fluorophores, that is, poly(di-n-octylfluorene; PF8), poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-bithiophene] and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], spontaneously physisorbed onto the neutral surface of 0.5-μm-sized spherical silica and four other ceramics in common nonpolar organic solvents within several hrs at room temperature. This process was observed via photoluminescence and excitation spectra. Attractive van der Waals interactions between the polymers and ceramics are responsible for the solution-phase physisorption. Surprisingly, the highest fraction (51–56%) of β-phase PF8 was found to deposit at the surface without thermal treatment.