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Second and third virial coefficients (A2 and A3, respectively) for cyclohexane solutions of linear polystyrene (benzyl-PS) samples, synthesized with benzyllithium (n-butyllithium/tetramethylethylenediamine/toluene ligand complex) as an initiator, were determined as functions of temperature and weight-average molecular weight Mw ranging from 710 to 7650. At the Θ temperature (34.5 °C), where A2 ) 0 for sufficiently high Mw, A2 decreased with lowering Mw, in contrast to the sharp increase reported for low molecular weight polystyrene with a butyl group (butyl-PS) at one of the chain ends. This molecular weight dependence of negative A 2 for benzyl-PS was explained, without consideration of end effects, by the recent theory of Yamakawa and Yoshizaki for the helical wormlike chain with three-segment interactions, while the upswing of positive A 2 for butyl-PS was ascribed primarily to the butyl end effect that surpasses the ternary cluster effect. The A3 values for both benzyl-and butyl-PS were positive and increased with decreasing Mw, showing significant end effects. The end effect in the former was larger than that in the latter, indicating that the three-segment interaction among a chain-end unit and two middle units for benzyl-PS is larger than that for butyl-PS.

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