Total Ion Counts

POLYISOPRENE/POLY(c-£e)BUTADIENE (50/50 copolymer)

see insert in spectrum (X and Y represent integers, the values of which may change throughout the polymer matrix)

B.F. Goodrich, USA

solution in tetrahydrofuran; 10 yg

Teq 510°C; tj 5s; tj 10s; Eel 12eV; expansion chamber removed (Extranuclear 5000-1 Py-MS system)

5 X 104

REMARKS - The dominant pyrolysis mechanism appears to be depolymerisation resulting in the formation of large monomer, medium-sized dimer and small trimer peaks. Many of the other signals including all odd-numbered mass peaks, appear to be due to residual electron impact fragmentation (mainly loss of 15 daltons from the monomer and oligomer ions). In addition, some peaks may be due to thermal degradation reactions. The conspicuous peaks at m/z 220 and m/z 205 represent the molecular ion and (M-15) fragment ion of dibutylhydroxytoluene, a common stabilizer in tetrahydrofuran solvents. Note the relatively low abundance of mixed oligomer signals (e.g. the lack of a marked butadiene-isoprene dimer at m/z 122) indicating a block co-polymer structure.

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