It was found that use of hydrophilic poly(ethylene oxide) (PEO) as a dispersion agent could disstack phthalocyanine IPC) in water and enhance its luminescence quantum yield. A combination of laser light scattering, UV-vis, and fluorescence spectroscopy was used to study the PEO/PC interaction. Our results revealed that, for a given weight concentration, long PEO chains were more effective than shorter ones to disstack PC into individual molecules. The PEO concentration dependence of UV-vis and fluorescence emission spectra showed that one long PEO chain (M-w similar to 10 000 g/mol) is as effective as 25 short PEO chains (M-w similar to 2000 g/mol).