An instrument was constructed for studies of self diffusion of polymer in solution. The self diffusion coefficient, D
s, could be measured by using either of the fluorescence recovery after pattern photo-bleaching (FRAPP) or the forced Rayleigh scattering (FRS) techniques with slightly different experimental setups. These techniques are similar in parinciple. In both techniques, D
s is estimated from the relaxation process of intensity of light (fluorescence or diffracted light) due to redistribution after formation of grating-like pattern by photo-bleaching of polymers labeled with photo-bleachable dyes. Capability of the instrument was demonstrated from D
s measurements on solutions of two narrow distribution polystyrene samples with M
s=43,900 and 355,000 in dibutylphthalate in the range of polymer concentration from 1 to 50 wt%. The time variation of intensity of light from the two techniques, FRAPP and FRS, could be fitted with single exponential curves suitable for respective theoretical prediction. Values of D
s estimated with the two methods agreed with each other over the range of D
s values from 10
-8 to 10
-12cm
2/s.
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