Measurement of functional group and molecular weight interrelations by GPC/IR

When the effluent from a gel permeation chromatograph is analyzed by infrared absorbance on a continuous basis (GPC/IR), individual functional groups can be followed. Successive analyses at different characteristic wavelengths permit the estimation of group distribution within a molecular weight distribution. The use of low molecular weight internal standards that combine the functional groups of interest is shown to enhance the reliability of the method. A mixture of polymers of styrene and methyl methacrylate and a copolymer of the two have been analyzed with phenyl benzoate as an internal standard. It is demonstrated also that the relative concentration of hydroxyl and ether groups can be monitored in a mixture of poly(ethylene oxide) homologs. Among the polymer substituent groups successfully analyzed in GPC/IR with trichloroethylene as solvent are OH, COC, SiOSi, CF, CH2, carboxyl, and phenyl.