Poly(-N,N-dimethylaminomethyl styrene) is a basic polmer which has basic dissociation groups. The effect of eluent composition is shown below:
Eluent a)------This eluent is a typical one for polymer analysis, however, this eluent is not good for this polymer. The polymer is adsorbed by the packing materials and will not elute because dissociation of amino groups in the polymer is suppressed.
Eluent b)------By the addition of chloroform, the polarity of the eluent is lowered and the adsorption problem by the packing materials is apparently solved. However, comparing the calibration curve of polystyrene of the eluent b) with that of THF, it is confirmed that some amount of adsorption still exists.
Eluent c)------N-methylpyrolidon (NMP) which is commonly used for the analysis of high polarity polymers is used as the eluent. To cancel ionic interaction between NMP and sample, LiBr is added, and, to suppress dissociation of sample, ethylenediamine is added. The obtained GPC pattern is very good and free from hydrophobic adsorption and ionic interaction.
As described in the above, not only the selection of column type but also the selection of eluent composition is very important for the analysis of ionic polymers. GPC KD-800 series are suited to the polar substances which are dissolved in polar solvents such as DMF, DMAc, NMP and ethylacetate.


Sample: Poly(-N,N-dimethylaminomethyl styrene)

Columns      : Shodex GPC KD-804 + KD-803 (8.0 mm I.D. x 300 mm each)
Eluent       : a) 5 mM LiBr in DMF
               b) 5 mM LiBr in DMF/CHCl3=50/50
               c) (5 mM LiBr + 50 mM Ethylenediamine) in NMP
Flow rate    : 1.0 mL/min
Detector     : RI
Column temp. : Room temp.