Long polymer chains in good solvent: beyond the universal limit

We analyze the effects of finite segment size and weak chain stiffness on the properties of polymer solutions in the dilute lirait. We consider both weak coupling (cross over from G- to excluded volume - conditions) and strong coupling (very good solvents), pointing out that the renormalization group in its standard field theoretic implementation allows for two universal branches corresponding to these two different situations. The strong coupling branch implicitly relies on the existence of a finite segment size, a feature which however does not explicitly show up in the renormalized results. Beyond the leading `corrections to scaling' described by the standard renormalization group flow, the strong coupling branch necessarily is affected by nonuniversal corrections. In field theoretic renormalization we include the first order effects of finite segment size or stiffness in terras of an expansion of the scaling functions about the universal limit. We compare to direct renormalization, where finite segment size or stiffness are included into the renormalization group equations. This somewhat magnifies the effects, but still the nonuniversal corrections are negligible for chains longer than about 500 freely rotating units. Qualitatively the effects in both renormalization schemes are the saine, consistent with experimental or Monte Carlo results