Thermal decomposition of poly(sec-amyl methacrylate)

The thermal decomposition of poly(sec-amyl methacrylate) is studied by simultaneous thermogravimetry-gas chromatography-mass spectrometry and by pyrolysis-gas chromatography. The TG curve has four distinct breaks and a plateau. Results of the identification of the evolved gas at the individual break...
Ausführliche Beschreibung

The thermal decomposition of poly(sec-amyl methacrylate) is studied by simultaneous thermogravimetry-gas chromatography-mass spectrometry and by pyrolysis-gas chromatography. The TG curve has four distinct breaks and a plateau. Results of the identification of the evolved gas at the individual breaks by GC-MS techniques lead to the conclusion that these breaks correspond to the individual processes in the decomposition mechanism like that of poly(tert-butyl methacrylate): the first break, the depolymerization initiated at the unsaturated chain ends; the second break, the depolymerization initiated at the saturated chain ends; the third break, the ester decomposition; the plateau, the inhibition of decomposition by the formation of poly(methacrylic anhydride); the fourth break, the decomposition of poly(methacrylic anhydride). The extent of ester decomposition is related to the substituent constants based on Hammett equation. The ester decomposition product is separated into three pentene isomers by pyrolysis-gas chromatography: trans-2-pentene, cis-2-pentene, and 1-pentene. As raising decomposition temperature, the composition ratio of trans-2-pentene decreases and becomes constant above 620 K, and the composition ratios of cis-2-pentene and 1-pentene increase and also become constant above 620 K. These results are accounted for by mobility of atoms included in the substituent at forming a ring transition state. Ausführliche Beschreibung