Measurement of Molecular Weight Distribution of Poly(Ethylene Imine)

Comparison of chromatograms of poly(ethylene imine) depending on the concentration of sodium nitrate in the eluent is shown in Fig.1. In the case of 0.02M - 0.05M sodium nitrate in the eluent, the constituent of high molecular weight of poly(ethylene imine) is adsorbed to the gel material and is not eluted from a column. When the salt concentration of sodium nitrate is more than 0.1M, the adsorption of a sample is suppressed and a right chromatogram is obtained. The relation between the molecular weight of poly(ethylene imine) and elution volume with SEC/MALS is shown in Fig.2. In the case of 0.1M - 0.2M sodium nitrate in eluent, poly(ethylene imine) is separated in the molecular weight order. The relation between the RMS radius (size of the molecule in the solution) of poly(ethylene imine) and elution volume with SEC/MALS is shown in Fig.3. When the concentration of sodium nitrate is lower than 0.05M, the constituent of high molecular weight of poly(ethylene imine) is adsorbed to the gel material and is not eluted, and the RMS radius of eluted polymer becomes large. When the salt concentration is 0.1M - 0.2M, the influence of the diffusion of molecule is decreasing according to the salt concentration and separation is performed in the molecule size order. From the above result. For the measurement conditions of poly(ethylene imine) with OHpak SB-806M HQ, the eluent of 0.5M acetic acid + 0.1M - 0.2M sodium nitrate is sutable for this analysis.







Sample: 0.2% Poly(ethylene imine), 100micro-L

Columns      : Shodex OHpak SB-806M HQ (8.0mmID*300mm) x 2
Eluent       : 0.5M CH3COOH + nM NaNO3 aq.
Flow rate    : 1.0mL/min
Detector     : Shodex RI, MALS(Multi-Angle Laser Light Scattering Detector)
Column temp. : 40deg-C