Designation:D4001−13StandardTestMethodforDeterminationofWeight-AverageMolecularWeightofPolymersByLightScattering1ThisstandardisissuedunderthefixeddesignationD4001;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope*1.1Thistestmethoddescribesthetestproceduresfordeterminingtheweight-averagemolecularweightMwofpoly-mersbylightscattering.Itisapplicabletoallnonionichomopolymers(linearorbranched)thatdissolvecompletelywithoutreactionordegradationtoformstablesolutions.Copolymersandpolyelectrolytesarenotwithinitsscope.Theprocedurealsoallowsthedeterminationofthesecondvirialcoefficient,A2,whichisameasureofpolymer-solventinteractions,andtheroot-mean-squareradiusofgyration(s2)1/2,whichisameasureofthedimensionsofthepolymerchain.1.2Themolecular-weightrangeforlightscatteringis,tosomeextent,determinedbythesizeofthedissolvedpolymermoleculesandtherefractiveindicesofsolventandpolymer.Arangefrequentlystatedis10,000to10,000,000,isoftenextendedineitherdirectionwithsuitablesystemsandbytheuseofspecialtechniques.1.2.1Thelowerlimittomolecularweightresultsfromlowlevelsofexcesssolutionscatteringoverthatofthesolvent.Thegreaterthespecificrefractiveincrementdn/dc(differenceinrefractiveindicesofsolutionandsolventperunitconcentration),thegreaterthelevelofsolutionscatteringandthelowerthemolecularweightthatshallbedeterminedwithagivenprecision.1.2.2Theupperlimittomolecularweightresultsfromtheangulardependenceofthesolutionscattering,whichisdeter-minedbythemolecularsize.Forsufficientlylargemolecules,measurementsmustbemadeatsmallscatteringangles,whichareultimatelyoutsidetherangeofthephotometerused.1.3ThevaluesstatedinSIunitsaretoberegardedasstandard.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishapp...
