ABSTRACT
Theprocedureofdeterminationofparameterviscometodeterminationofparameter8for frozen(at277K)solutionofspin-markedpolymer.Thisparameterdependsondipole-dipolebroadeningofEPR-spectraofspinmarkersandprobes[12]:
8=dtld-(dtld)o(2) wheredtld-theratioofsumintensityofendcomponentsofspectratointensityofcentralcomponentatgivenconcentrationofparamagneticsites;(dtld)o-thevalueofparameterdtldatsuchconcentrationatwhichdipolebroadeningisnotrevealedinEPR-spectra(Figure23.1).Thenthesolutionofspinprobeisselected(solutionofnitroxylradicalnotbondedwithmacromolecule)inthe samesolventinwhichparameterd1/dhasat77Kthesamevalue,asforsolutionofspin-marked polymer;spectraofmarkersandprobesarenormalizedbyequalconcentrationofparamagnetic sitesandtheratioofintensitiesofcentralcomponentsofspectraofprobe(dp)andmarker(dt)is determined.Thisratioiscomparedwiththeoreticaldependencesofratiodpld1onparameter8calculatedforthreeconformationalstatesofmacromolecule:Gaussball,swollenballandglobule (Figure23.2).Suchcomparisonallowsselectingformthreeconformationalstatesofpolymerchain.
Figure23.1.ExamplesofEPR-spectraofsolutionsofspin-markedpoly-4-vinylpyridine(PVP-1,polymerizationdegreeP=500)(0,5mass%)inmethanolat77K.Thenumberofmarkersonpolymerchain:85(I) and3(2).
