Egypt. J. of Appl. Sci., 21, 30 (2006) Analysis of Excluded Volume Effect for Poly (n-alkyl acrylates) in Tetrahydrofuran Salem M. Aqeel Dept. of Chemistry, Faculty of Applied Science, Thamar University, P. O. Box 87246, Thamar , Yemen .com yahoo el@ salemaqe E. Mail: Abstract: The reported data for the solution properties of poly(methyl, ethyl, butyl, hexyl and lauryl acrylates) were applied to analysis the excluded volume effect by using Flory ' s, Fixman's, Kurata's and Yamakawa's theory . Parameters A and B, which describe the short- range and long-range interaction between segments, respectively have been evaluated. Values of expansion factor,  as a function of excluded volume parameter, z have been calculated using A and B parameters. According to our results, the  3 - type equation appears to provide a better fit than  5 – type and  2 - type equation for z>0.5. Keywords: poly(methyl, ethyl, butyl, hexyl and lauryl acrylates), unperturbed dimensions, expansion factor, excluded volume. INTRODUCTION Dilute solution properties of polymer chain should be investigated from the view point of molecule interactions of segment. Usually static properties such as dimensions of polymer chain have been examined from measurements of overall properties such as intrinsic viscosities by means of statistical mechanics such as so- called two – parameter theory [1-4]. The dimensions of polymer chains in solution are greatly influence by interaction between chain elements. These interactions are conveniently divided in two classes: The short-range interactions are those between atoms or groups separated by only a small number of valence bonds. The long-range interactions on the other hand, are those between non-bonded groups, which are separated in the basic chain structure by