Low polydispersive polystyrenes, tethered with pyrene (Py-PS) or naphthalene (Na-PS) at one end of the chain, were synthesized by atom transform radical polymerization (ATRP). The fluorescence emission spectra of Py-PS in THF were measured with different amount of water added. The results indicate that the "monomer" fluorescence intensity (I_M) of pyrene increased progressively with the increase of water content; and as the water content reached a certain amount, the emission of pyrene excimer was observed, whose intensity (I_E) increased when water was further added, until a macroscopical phase separation appeared. The critical added water contents for Py-PS at three concentrations were obtained from the changes of I_E/I_M and I_1/I_3 with the addition of water. Nonradiative energy transfer (NRET) was also exploited for a mixture of Py-PS and Na-PS in THF. The results may help to understand the aggregation of PS, as well as copolymers containing polystyrene block in solution containing different amount of water.

Key words: POLYSTYRENE, AGGREGALES, PYRENE, NAPHTHALENE, FLUORESCENCE