To investigate the influence of molecular structure such as side chain on phase separation process in solution, naphthalene-labeled poly (octadecyl vinyl ether) (PODVE) with long side chains was synthesized by living cationic polymerization. Rayleigh Light scattering (RLS) and photoluminescence (PL.) studies indicated that side chain played a dominant role in phase separation process in PODVE/dichloromethane system. According to the results of RLS and PL spectra, it was found that PODVE chains changed from expanded coils to collapsed globules and then aggregated. At C = 0.2 g/L, the long side chain of PODVE (102) separated out from nonpolar solvent below 7.2 degrees C, which directly caused phase separation in solution. In addition, the phase separation temperature slightly increased when the concentration of PODVE (102) solution varies from 0.05 g/L to 0.2 g/L, and more obviously (i.e., from 3.5 degrees C to 7.2 degrees C) as the molecular weight increases from 4300 to 10 200. The Activation energy of phase separation of the PODVE solution was -270.09 kJ/mol estimated by means of Avrami equation and Arrhenius formula. (C) 2011 Elsevier Ltd. All rights reserved.