2011 Volume 60 Issue 3 Pages 239-244
Chemical structures in terminal-modified and branched bisphenol A (BPA) type polycarbonate (PC) samples were characterized by pyrolysis-gas chromatography in the presence of tetramethylammonium hydroxide using ca. 50 μg samples. In the case of terminal-modified PC samples, methyl derivatives of the main component (BPA), the ordinary p-tert-butylphenoxy (PTBP) terminal, and the modified p-tert-cumylphenoxy terminal were quantitatively formed through thermally assisted hydrolysis and methylation of the polymer chain, and quantitatively observed in the pyrograms. The chemical compositions including end groups and number-average molecular weights (Mn) of the PC samples were calculated from the relative peak intensity of these products with less than 5% of relative standard deviations, and were consistent with those obtained by 13C-NMR and size exclusion chromatography (SEC), respectively. Similarly, the methyl derivative of the branching component, 1,1,1-tri(4-hydroxyphenyl)ethane, was clearly observed in the pyrogram of the branched PC sample, together with those of the BPA main chain and PTBP terminal units. The chemical composition of the branched PC sample estimated from the relative intensities of these methyl derivatives, PTBP : BPA : THPE = 3.7 : 95.8 : 0.5 (mol%), was in good agreement with that by an HPLC analysis of the hydrolyzates of the PC sample. In addition, the average numbers of terminals and branching in a PC molecule were calculated to be 2.3 and 0.33, respectively, based on the relationship between the PTBP and THPE contents. Combining the chemical composition and the average branch number, Mn of the branched PC was estimated to be 1.6 × 104, which was comparable to that by SEC. Meanwhile, the average branch number, 0.33, suggests that an average of ca. one third PC molecules have one branching in a molecule, while the remaining two thirds should be linear molecules without any branching in the branched PC sample.
