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Calibration curves for poly( acrylonitrile) (PAN) and poly(v1-nyipyrroiidone) (PVP) were constructed by using polyethylene oxide (PEO) as primary standards. Molecular weight of PEO at retentlon volume I , (MA),, was converted to molecular weight of PAN or PVP, (M&, by the equation M, = 8(MA);.Constants 8 and f were calculated by using two polymer samples of PAN or PVP of known molecular weights and the PEO Calibration curve. Constants 8 and t for PAN were 12.76 and 0.866, and those for PVP were 3.15 and 0.959. The Mark-Houwink parameters for PAN and PVP were estimated by the SEC method Independently of those for PEO. The relationships between [VIM and retention volume for those polymers suggest that PVP elutes under the mechanism of size excluslon, while PAN suffers the secondary effects even if LlBr Is added to dhnethylformamlde (DMF). Elution behavior of PAN and PVP In DMF and the effect of adding LlBr to DMF are discussed.Poly(acrylonitri1e) (PAN) and poly(vinylpyrro1idone) (PVP) are important polymers as synthetic fibers and as capsular material for medical use, respectively, and accurate determination of molecular weight for these polymers is of primary importance for process and quality controls. Size exclusion chromatography (SEC) is a widely used analytical technique for the characterization of synthetic polymers. Most commonly employed solvents for SEC are tetrahydrofuran (THF) and chloroform, both of which, however, do not dissolve these two polymers. N,N-Dimethylformamide (DMF) has found widespread application in SEC analysis, but it has also been noted that peculiarities of elution behavior for such polar polymers are directly related to the use of DMF. The addition of lithium bromide (LiBr) to DMF has been attempted to eliminate these peculiarities (1-3).In SEC, the construction of a calibration curve for the column system is required at first and a series of polystyrenes (PS) of relatively monodisperse character are mostly employed for this purpose. Because of the poor solubility of PS in DMF, the retardation of retention volume (V,) for PS was observed (3), and as the result of the retardation, the divergence between the universal calibration curves for PS and PAN obtained by plotting [VIM and V , (4) is a matter of course. The abnormality of elution of PS in DMF may be explained by partitioning or adsorption of PS on the gel. Polar polymers such as poly(ethy1ene oxide) (PEO) must be employed as standards. Comparison of the PEO calibration curve in DMF with one obtained on the same column set in THF revealed no difference between them (5).To calculate the molecular weight averages for any polymers other than PEO by a PEO calibration curve, it is necessary to transform molecular weight units of PEO in the curve to those for the polymer specified. One of the techniques used to transform the molecular weight units is so-called "universal calibration" (6), and this method has been shown to have wide applicability. In order to aply the universal calibration method, however, it must be clear that the elu...

ABSTRRCTThe compositional heterogeneity of styrene-methylmethacrylate copolymer has been evaluated by a UV-RI dual-detector method and by a RI detector-pyrolysis-gas chromatographic method and problems associated with the determination of the chemical heterogeneity by a UV-RI method are discussed. The quotient of signals H(UV)/H(RI) of both the detectors ( U V and RI) for polystyrene increased at the extreme parts of the molecular weight distribution owing to nonlinearity of UV response.The correction of the quotient of signals of both detectors for the copolymer was proposed.The UV and RI response factors for the copolymer were supposed to differ from those for homopolymers. Reproducibility for the detector responses influences the values of chemical heterogeneity much more than expected.To overcome these problems, the detection method to obtain each composition independently using different detectors will be preferable.

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