Forasystemofflexiblepolymermolecules,theconceptsoftwoconcentrations,namelythesegmentalandthemolecularconcentrations,havebeenproposedinthispaper.Theformerisequivalenttothevolumefraction.Thelattercanbedefinedasthenumberofthegravitycentersofmacromoleculesinaunitvolume.Thetwoconcentrationsshouldbecorrelatedwitheachotherbytheconformationalfunctionofthepolymerchainandshouldbediscussedindifferentthermodynamicequations.OnthebasisoftheseconceptsithasbeenprovedthattheFlory-Hugginsentropyofmixingshouldbetheresultofthemixing'idealgasesofthegravitycentersofmacromolecules'.Thegeneralcorrelationbetweenthefreeenergyofmixingandthescatteringfunction(structuralfactor)ofpolymerblendshasbeenstudiedbasedonthegeneralfluctuationtheory.WhentheFlory-Hugginsfreeenergyofmixingisadopted,thedeGennesscatteringfunctionofapolymerblendcanbederived.
