The interpenetration of two excludedhyphen;volume chain molecules of different size in dilute solution is studied via scaling and renormalization methods. The chains are found to interpenetrate much more strongly than smoothedhyphen;density models suggest, in accordance with recent work by Khokhlov. The pair correlation funtiong(r) goes to zero at the origin only as a weak power ofr. This power is related to Des Cloizeauxrsquo;s exponents Vthgr;idescribingintrachain correlations. The power is also related to the scaling exponents of star polymers. The mutual excluded volumeMSLof two chains with greatly different length is proportional to the volume of the smaller chain and to the mass of the larger. ThusMSLis much smaller than a smoothed density model would predict. We discuss which chain correlations give rise to this small MSL. The universal coefficient relatingMSLto the radius of gyration of the smaller chain is strongly dependent on the dimensiondof space, according to our secondhyphen;order expansion in 4hyphen;d. The interpenetration behavior predicted here affects measurable thermodynamic, scattering, and physicalndash;chemical properties of the solution.
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