Role of back-biting for generation of hybrid dimers and trimers on flash pyrolysis of poly(styrene-co-methacrylonitrile)

The role of the back-biting reaction for generation of dimers and trimers on flash pyrolysis of poly(styrene-co-methacrylonitrile) by pyrolysis gas chromatography with the use of a Curie-point pyrolyzer has been investigated. Yields of each monomer, dimer, and trimer changed depending on the sequence distribution as well as on copolymer composition and pyrolysis temperature. The degradation behavior was explained by the competition between the back-biting reaction and depolymerization. It was found that the hybrid dimers and trimers were produced mainly by the back-biting reaction, which was followed by β-scission, and hence yields of hybrid dimers and trimers correctly reflect the sequence distribution of the copolymer of styrene and methacrylonitrile without interference from the second reaction of monomers regenerated in the flash pyrolysis. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2747–2753, 1999     

Identification of Polyethylene by Differential Scanning Calorimetry: Application to forensic science

A forensic sample consisting of melt-recrystallized polymers that was recovered from the scene of a fire in a factory was identified by differential scanning calorimetry. The factory commonly used two kinds of film sheets, A and B, made by different manufacturers. It was necessary to decide whether the forensic sample related to material A or B. The forensic sample and reference samples of materials A and B were subjected to infrared spectroscopy and pyrolysis gas chromatograph mass spectrometry measurements, which revealed their polyethylene nature. The thermal behaviour of the samples was examined by differential scanning calorimetry (DSC) and they were found to be blends of two kinds of polyethylenes, low-density polyethylene and linear low-density polyethylene. The samples could be identified and distinguished from each other via the DSC measurements.This revised version was published online in November 2005 with corrections to the Cover Date.     

Characterization of poly(styrene‐co‐methacrylonitrile)s obtained by low‐temperature radiation polymerization and thermal degradation behavior measured by Py‐GC and CRTG

Poly(styrene‐co‐methacrylonitrile)s were polymerized in solutions with different polarities (n‐hexane and THF) by low‐temperature γ‐ray irradiation polymerization in a temperature range of −83.6–30 °C. It was found by IR measurement that the composition of the copolymers changed remarkably due to the effects of the polarity of solvents and the polymerization temperature. The thermal degradation behavior in the flash pyrolysis and in the continuous heating pyrolysis of these copolymers was measured by Py‐GC and controlled rate thermogravimetry (CRTG). The effects of the copolymer composition and sequence distribution on the thermal degradation behavior were investigated. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3569–3577, 2000