Distribution analysis of carboxyl groups in polymer by a derivatization/electron probe X-ray micro-analysis

In order to determine the distribution of a small amount of carboxyl groups formed by the oxidation of polymers with micron-level lateral resolution using an analytic method, referred to as ''derivatization-electron probe X-ray microanalysis (EPMA)'', the suitable condition of the derivatization reaction with carboxyl groups in polymers was investigated. It was found that carboxyl groups in polymer were derivatized selectively using gas-phase esterification with 2,2,2-tribromoethanol (TEE). Pyridine was used as a catalyst, and dicyclohexylcarbodiimide (DCC) was used as a dehydration agent. The most suitable amounts of TBE, pyridine, and DCC in a 50 ml reaction vessel were 70 mg, 70 mu g, and 50 mg, respectively. After setting a sample in the vessel without directly contacting the reagents, by heating the reagents and the sample at ll0 degrees C for 2 hours, the highest reaction yield and selectivity were obtained. By derivatization-EPMA using this derivatization condition, an analysis of the distributions of a small amount of carboxyl groups in polymers with 3 mu m lateral resolution has become feasible. For example, in the case of degraded polyethylene (PE), 0.6 units of carboxyl groups per 10,000 ethylene units can be detected. The actual applications to the depth analysis of degraded PE and Nylon-6 have proved that this method is useful for the studies on polymer degradation.