Abstract
In gel permeation chromatography (GPC), polymers have to be dissolved in an appropriate eluent which has low viscosity and high differential refractive index to the polymers. The eluent should be also satisfied for many other experimental requirements. In this study, we conpared various eluents, i.e., ο-chlorophenol (OCP), an OCP/α-chloronaphthalene (α-CN) mixture, hexafluoroisopropanol (HFIP), HFIP/0.01 MCF3COONa, and a HFIP/toluene mixture, for this purpose. A home-made GPC apparatus equipped with a Showadenko Model SE-11 refractive index detector was used. GPC separations were made by using a set of two columns of Toyosoda TSK-GEL GMH6. The temperature of column oven was varied depending upon eluents. The detector was operated at ambient temperature. Apparent chromatograms were good in OCP as eluent. However, the peakpositions and the widths of the chromatograms varied with injections. To improve this poor reproducibility, α-CN was added into OCP. The chromatograms obtained thus, however, showed high concentration dependence, although the peak positions were reproducible. Generally, HFIP is a good solvent for polyamides. Pure HFIP, unfortunately, did not provide normal chromatograms : an unknown shoulder or peak appeared in lower elution count region. To eliminate this abnormal phenomenon, a small amount of CF3COONa was added into HFIP with reference to a published paper. The result was normal. We can obtain the molecular weight distribution curves from the chromatograms, if a calibration curve was prepared for Nylon 12. Unfortunately, polystyrene was insoluble in this eluent. Therefore, it was impossible to prepare or estimate the calibration curve of Nylon 12 from that of polystyrene. The most recommendable eluent was a HFIP/toluene mixture (2/8 in volume). Reproducible chromatograms were obtained together with the calibration curve of polystyrene. We conclude that a HFIP/toluene mixture was preferable to phenols as an eluent of GPC for Nylon 12.
