A new coil-rod-coil copolymer is synthesized via Sonogashira coupling using one-step methodology. The copolymer PEG-OEPETPT-PEG constitutes of poly(ethylene glycol) (PEG) as the coil block, and oligo[p-(ethynylenephenyleneethynylene)-alt-(thienylenepyridazinylenethienylene)] (OEPETPT) as the rod segment. The conjugated polymer PEPETPT with the same conjugated building blocks is also synthesized for comparison. The structures of both polymers are confirmed by NMR, combined with other characterizations. PEG-OEPETPT-PEG has a 12 nm blue-shift in the emission maximum compared with that of PEPETPT, and a higher quantum yield of fluorescence in THF. PEG-OEPETPTE-PEG tolerates up to 20% water content in H2O/THF mixed solvent without significantly changing the emission wavelength and intensity, while the fluorescence of PEPETPT is dramatically quenched by a very small quantity of water. Further photophysical studies about these two polymers indicate that the introduction of PEG coils onto the conjugated block retards the water-induced-aggregation and therefore improves the fluorescence stability of PEG-OEPETPT-PEG. (c) 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013, 51, 1636-1644