The principle of absolute quantification for size exclusion chromatography (SEC) with refractive index-light scattering (RI-LS) dual detectors was discussed with emphasis on the importance of the injected mass of the sample.By the measurement of the response constant of dual detectors for the injected whole sample

the specific refractive index increment dn/dc and the absolute weight average molecular weight (Mw) could be simultaneously determined.The proposed data treatment procedures are first applied to a series of narrow MWD polystyrene (PS) samples for determining the values of dndc and Mw.The experimental relationship between dn/dc and Mw for PS is in coincidence with the theoretical formula derived from the end group effect.The correction of dn/dc when Mw104 must be considered.The proposed method is not only useful for homopolymers

but is also applicable to polymer mixture and blends.Regarding an unlike polymer mixture with a given composition as a single solute

the specific refractive index increment and the absolute weight average molecular weight of the polymer mixture can be measured to decide whether molecular association between the two components happens or not.The method is illustrated by the system of poly(methyl-methacrylate) and polystyrene (PMMA/PS) in THF solution.PMMA chains will partially associate with PS chains to form complexes.The Mw values of PMMA/PS mixtures in THF show a great positive deviation from the linear composition addition rule.The deviation is attributed to the formation of PMMA/PS complex.The complex formation could be described by a simple reaction scheme of nA+mB=AnBm.Analyzing and fitting the experimental data yields:n=3

m=1/3 and an association constant of Ka=4.6×105.